本文作者為薛世卿（Thomas Hsueh，X：@guiltygyoza）。他曾創辦 Topology，研究領域涵蓋加密原生遊戲、自主世界與可驗證計算；2025 年起轉向應用科學，近來投入量子電腦與AI的研究。他的部落格是 guiltygyoza.xyz。

本文首發於 Parity官網，電子報為轉載；另有英文版。遙望集是 Parity 的研究資助計畫。

1. 因果局域與細胞自動機

這個世界上，沒有任何東西（有形的、無形的、原子或位元）能夠以超光速移動，對吧？

我們活在狹義相對論被證實之後的時代。我們相信因果關係：結果必定發生在原因之後。我們相信任何因果效應的傳遞，速度都不能超過真空光速。我們熟習閔考斯基圖，理解「因」必定在「果」的過去光錐裡。因果效應是以有限的速度傳播的，不能忽視距離的存在。這樣的認知模型，可稱為「因果局域性」。

「因果局域性」這個認知模型如此普及，以至於在電腦科學領域裡，Leslie Lamport 定義了「發生在前」關係（happened-before relation，記作 →）；後來的研究者（Ahamad 等人，1995 年）以它為基礎，為分散式系統定義了「因果一致性」：給定一個有許多進程的系統，給定任兩個操作 A 和 B 滿足 A→B，如果系統中任何一個進程，都保證先看到 A 再看到 B，則這個系統是「因果一致」的。在這樣的系統裡，所有進程都看到一樣的因果順序。

我們可以從電腦科學角度觀察「因果局域性」：細胞自動機。讓我們設計以下的細胞自動機規則：

• 在二維平面上，有兩顆大球，一顆在左，一顆在右。

• 左球和右球，在每一個時間步，都會各自投擲一枚 50-50 機率的硬幣，決定下一個時間步自己是什麼顏色。

• 一旦「量測」一顆球，該球就會凍結在量測瞬間的顏色，並且朝另一顆球發射一枚中介子，中介子攜帶自己的顏色。

• 被中介子碰到的球，會凍結成該色，並且將中介子吸收。

啟動這個細胞自動機，並在一段時間之後量測右球，你可能觀察到下面的結果：

你會發現左球顏色有兩種狀態：

1. 狀態一：量測右球之後、中介子尚未到達左球之前，左球的顏色是 50-50 隨機的紅與藍。

2. 狀態二：量測右球、中介子碰到左球之後，左球必定與右球同色。

在量測右球後，左球的顏色，取決於中介子移動速度。

在這個細胞自動機裡，所有規則都是針對相鄰格點而制定（每一格有八個鄰居，稱為 Moore 鄰域）。這項侷限讓細胞自動機必須遵守「因果局域性」，畢竟所有改變只能夠透過鄰居傳遞。中介子的移動速度恰好為「每一個時間步，移動一格」。「一步一格」的速度，是這個細胞自動機小宇宙裡的「真空光速」。而這個系統，可以被理解為「透過局域因果效應互動的系統」。

假如我們讓中介子以更快的速度移動，那麼，我們將更容易量到左右兩球顏色相同的情況。

現在，使用我們的想像力，考慮「時間步為無限小」的情形：兩球以「無限快」的速度在紅藍兩色之間隨機閃爍，中介子則以「無限快」的速度移動。

再次考慮上述實驗，我們發現狀態一消失了，只剩下狀態二。使用狄拉克符號（Dirac notation），將紅色表示為 、藍色表示為 ，則在時間步無限小的情形下，兩球顏色的量測統計，與下面這個量子態相同：

這行數學代表：有二分之一的機率，我們將測到兩球皆為紅色；另外二分之一的機率，將測到兩球皆為藍色。

中介子以「無限速度」移動，導致「因果效應」違背局域性、以無限速度傳播。這個使用細胞自動機的思考實驗，展示了「量子糾纏」的效果。

量測一顆球（因），另一顆球「立刻」凍結為同色（果），這個因果效應無視距離的瞬間傳播，愛因斯坦（Albert Einstein）稱之為「鬼魅般的超距作用」（spooky action at a distance）。

2. 愛因斯坦擔憂的超距力量

大谷翔平的指叉球，以直球球路前進，到本壘前卻快速掉落，落在好球帶右下角，再次誘騙打者揮棒落空。

有辦法準確計算指叉球的落點嗎？常識告訴我們，仔細考慮越多因素，並且不犯下任何計算上的錯誤，就能持續提高計算結果的準確度。首先，考慮棒球離手瞬間的速度向量。接下來，考慮棒球離手瞬間的角速度向量。如有需要，考慮棒球飛行過程中的每一刻，所在位置的地心引力、風向、氣壓、濕度等因素。考慮使用最精確的電腦，使用最小的網格，進行有限元素法模擬。我們相信，考慮越多因素，並保持計算嚴謹，就有辦法無限逼近真相。

這個信仰的一個必然結果（corollary）：如果計算結果偏離真相，而且我們確定並沒有犯下任何計算錯誤，那麼，必定還有應考慮而未考慮的因素作祟。

這個信仰，用更抽象一點的語言表示，就是「實在論」：宇宙裡一切事物都客觀實在。我們如果觀測一個系統 X，得到觀測結果 Y，是因為 X 在觀測前「本來」就有某種確定、實在的狀態值，透過我們的觀測手法得到 Y 的結果。

想像一個簡單的橫向捲軸遊戲：作為玩家，你處在地圖中的某處，你的視野有侷限，只能看到附近的樣貌，例如幾隻會走路的蘑菇人。然而，遊戲系統在背景裡，孜孜不倦的計算地圖裡所有事物的行為，不管那些事物有沒有出現在你的視野裡。這就是「實在論」的體現。

套用在宇宙的尺度，「實在論」告訴我們，無論是否受到有意識的主體觀察，宇宙的任一處，在任一時刻，都完美依照宇宙法則，老老實實的演變。

狡猾的遊戲設計師，在能力有限的運算平台上，想要創造豐富的遊戲體驗，老早就脫離了「實在論」。1985 年由任天堂推出的《超級瑪利歐兄弟》，並不遵守「實在論」。玩家在地圖某處，玩家視野被稱為 visible screen，比視野稍大的一個範圍被稱為 relevant screen。relevant screen 內的遊戲地圖才受到遊戲系統運算的青睞，逐幀更新；在那之外，怪物尚未誕生、事物被凍結在「初始狀態」。「玩家觀測不到的地方，就別計算了」這樣的作法，可以顯著節省記憶體與運算量，也對遊玩體驗沒有顯著影響。

然而，我們基本上不相信，宇宙也玩這套把戲、在不受觀測的地方胡作非為。我們基本上相信宇宙中一切的一切都孜孜不倦、像機械齒輪般精巧、準確的演變著。

將「實在論」和「因果局域性」結合，就是著名的「局域實在論」：一切存在都是客觀的，獨立於任何觀測，並且在某區域發生的事件，不能以超越光速的方式影響其他區域。

假如你此刻抱持這個信仰，認為理所當然，那麼你的認知已過時一百年了。一百年前，這個信仰就受到量子力學的挑戰。

挑戰實在論

1925 年春天，戴維森-革末實驗（Davisson–Germer experiment）發現，原本要探討的電子散射現象（你可以理解為微觀的撞球實驗），顯現超乎預期複雜的散射分佈。1926 年，他們得知德布羅意（Louis de Broglie）和薛丁格（Erwin Schrödinger）的量子力學理論，主張電子具有波的性質，被玻恩（Max Born）鼓勵往「波的繞射」而非「粒子散射」的方向研究。1927 年春天，戴維森和革末發表實驗結果：電子打在鎳晶體表面後散射回來，只在特定角度特別強，正是波被晶格繞射的特徵。

粒子具有波的特性，正是對實在論的挑戰。一個粒子，在一個時刻，只能實實在在的存在於一個地方。量子力學理論卻說，一個粒子的位置，並沒有實實在在的唯一存在，而是機率性的漫佈在空間中、由波動理論描述。

1927 年 10 月，在布魯塞爾舉辦、眾星雲集的第五次 Solvay 會議（Solvay Conference），主題為「電子和光子」。愛因斯坦和波耳（Niels Bohr）爭辯量子力學是否能夠完整描述宇宙一切行為。愛因斯坦認為不，波耳認為可。愛因斯坦針對電子繞射實驗，提出一個思考實驗：

• 製備一個系統，包含電子槍、狹縫、成像屏幕。

• 量子力學宣稱，宇宙只能告訴我們「電子穿過狹縫之後，在屏幕上某處出現的機率」；愛因斯坦認為這種只能給出機率、給不出精確位置的問題，是因為存在應考慮而未考慮的因素作祟（回想稍早我們對大谷翔平指叉球落點的討論）。

• 假如我們仔細觀察電子穿過狹縫時，狹縫的微小變化，例如狹縫被電子撞到而出現的微小反衝，那麼我們就能得知更多、超過量子力學極限的資訊，有利於推斷電子軌跡（回想稍早的討論：風向、氣壓、濕度！）。

波耳說，如果我們去精確觀察狹縫的反衝（動量），那麼量子力學的測不準原理表示，我們就無法擁有確切的狹縫位置資訊；由於繞射斑紋取決於狹縫位置，如果狹縫位置模糊，繞射圖像就會亂成一團，斑紋消失。

愛因斯坦並不滿意。他認為肯定有應考慮而未考慮的因素作祟。只有「機率」、沒有確定性這種事情，肯定是人類物理學的缺陷，宇宙不會使用這種不精確、擲骰子般的作法來演變。

海森堡（Werner Heisenberg）回憶：

• 愛因斯坦：「上帝不擲骰子。」（God does not play dice.）

• 波耳：「告訴上帝該怎麼管理世界，不是我們的事。」（It cannot be for us to tell God how he is to run the world.）

挑戰局域性

第五次 Solvay 會議上，愛因斯坦提出另一個思考實驗：

• 製備一個系統，包含電子槍、小孔、成像屏幕。

• 量子力學說，一顆電子穿過小孔後，形成一個半球形的「電子波」，電子存在位置可由這個波的形狀來描述；儘管電子波朝各方向擴散，實驗告訴我們，如果電子槍打出一顆電子，成像屏幕上只會出現一個點。

• 假如電子波就是電子在穿過小孔後的「實在」，那麼這個「實在」由波的形狀（散佈在空間中）從小孔出發，抵達屏幕後卻變成單點，有賴於某種無視距離的瞬間資訊傳遞方式：由於電子波涵蓋屏幕各處，屏幕測到電子的那一點，要瞬間通知屏幕其他所有位置：「嘿，電子在我這！你們那裡不准測到電子了！」

• 這種無視距離的力量，違背局域性，匪夷所思，根本見鬼了，是一種「鬼魅般的作用」。

量子力學同時挑戰「實在論」和「局域性」：事物沒有實在，只能以「機率」描述，並且存在違背局域性的超距力量來支配機率變化。

會議後多年，愛因斯坦依舊不滿。1935 年的 EPR 論文，就是想要挑戰這件事：想像兩顆粒子 A 和 B 交互作用後分開，總動量為零，彼此的距離也是確定的。我們可以自由選擇要測 A 的動量或者位置。如果我們選擇測量 A 的動量，套用動量守恆，就能瞬間得知 B 的動量。假如我們選擇測量 A 的位置，由於兩者的距離是確定的，因此不用測就能瞬間得知 B 的位置。基於這個結果，假如我們相信「局域性」，也就是對 A 的測量無法瞬間影響 B，那麼 B 的動量和位置各自都是實實在在的，才有可能不用測就瞬間知道結果。最後，因為量子力學宣稱位置和動量只能精確描述其一，因此量子力學不完備——肯定還有應考慮而未考慮的因素作祟。

把這些作祟的因素稱為「隱變量」，這個理論就稱為「局域隱變量理論」（local hidden-variable theory，LHVT）。1951 年，EPR 論文的思考實驗被玻姆（David Bohm）重述，黏在一起的兩顆粒子，分開後因為角動量守恆，測量其中一顆粒子沿著某軸向的自旋值，就能得知另一顆粒子沿著相同軸向的自旋值。自旋值是離散的 ，比起連續的位置和動量，更容易透過實驗精確檢驗。1964 年，貝爾（John Bell）將這個思考實驗，具體化為一條不等式，可透過實驗數據統計值來證偽 LHVT。1969 年，John Clauser 等人，把貝爾思考實驗中仰賴的一個嚴格條件拿掉（即兩邊沿同一方向測量時，結果必須完美反相關；真實的光源、偏振器與偵測器都做不到），設計出一個更容易實驗的版本、一條新的不等式，稱為 CHSH 不等式。

Bell 不等式（CHSH 及其變體）至今已被數十個實驗違反，例如 Freedman & Clauser 1972、Aspect et al. 1982、Weihs et al. 1998、Hensen et al. 2015。

這些實驗結果，建議我們放棄「局域實在論」的信仰。取而代之，宇宙中存在能夠無視距離、將因果效應瞬間傳遞的超距力量。正是這個超距力量，負責量子糾纏系統裡的狀態更新。回想稍早的細胞自動機實驗，把兩球想成是量子糾纏系統，則中介子的移動速度是無限的，因此測量其中一顆球的顏色，另一顆球的顏色在同一個瞬間就被凍結為相同顏色。

3. 駕馭超距力量

CHSH 測試與不等式

讓我們首先理解 CHSH 不等式：。解釋如下。

Alice 和 Bob 兩名實驗者分隔兩地，中間有一對黏在一起的雙胞胎粒子。突然，這對雙胞胎分裂了，兩顆粒子各自朝向一名實驗者飛去。實驗者在乎的是這些粒子的自旋值，並且各自挑選兩個方向進行測量。例如，Alice 挑選的方向一是地面往天空的垂直方向，方向二則是與地面平行的右手方向。兩名實驗者可以任意挑選自己喜愛的方向。粒子自旋值測量的結果，不管是哪名實驗者、沿著哪個方向測量，結果只有可能是 +1 或 -1。+1 代表「測出粒子沿著測量方向自旋！」；-1 則代表「測出粒子沿著測量方向的反方向自旋！」

現在使用變數進行討論。Alice 的兩個測量方向為 、。沿著 測量時的結果為 ，沿著 測量的結果則為 ，。Bob 的方向則是 、，結果為 、，。Alice 和 Bob 將進行這個實驗許多次，各自記錄下測量結果，最後進行統計分析。

每一次實驗，Alice 和 Bob 的測量方向組合，其實只有四種可能：、、、。每一次實驗，Alice 和 Bob 的測量結果進行相乘，只有兩種可能：+1 或 -1。

CHSH 不等式的左邊是 ，其中 是平均值。這些平均值是什麼意思呢？以 為例：將所有實驗中，Alice 和 Bob 的測量組合為 的實驗挑出來，把每一次實驗的兩邊測量結果相乘，然後取平均。

因此這個式子的意義，就是從眾多實驗數據中，產出四種平均值，然後將前三種加在一起，再扣掉第四種。

假如我們相信「局域實在論」，代表粒子在分離之後，不再交換資訊，各自帶著自己的「實在值」前往各自的實驗者。例如，朝向 Bob 飛去的粒子，在剝離雙胞胎時就已經決定：「待會如果 Bob 測 方向的話，我要給他 +1 的結果；如果他測 方向，我則給他 -1。」透過窮舉這對雙胞胎粒子所有可能的「決定」，CHSH 論文的作者發現「局域實在論」會導致 。

然而，至今已有數十個實驗的統計數據違背了上述不等式。

CHSH 遊戲

有些學者的焦點並不在於「局域實在論」，畢竟他們（或者他們的指導老師）早在 Solvay 會議的年代就已經被波耳說服了。他們的焦點在於量子資訊技術：量子糾纏這種超距作用，在資訊領域有什麼用處？

在 2000 年代初，CHSH 不等式的實驗，被重述成一種合作式的資訊遊戲：Alice 和 Bob 分隔兩地，不能通訊；一名中立的裁判，給兩人各自提供一個隨機位元（值為 x、y），並要求兩人各自回覆給裁判一個位元（值為 a、b）。Alice 和 Bob 的獲勝條件是：

• 如果 x 和 y 都是 1，那麼 a 和 b 必須不同。

• 如果 x 和 y 是另外三種可能，那麼 a 和 b 必須相同。

濃縮為一個式子表示：。

有趣的是，因為量子糾纏不算通訊，遊戲允許 Alice 和 Bob 共享、操作一對糾纏的量子（想像稍早細胞自動機裡的左右兩球，Alice 和 Bob 可以各執一顆）。

Alice 和 Bob 該怎麼玩呢？考慮遊戲的難處，兩人在第一種情況下必須給出相異的答案，在剩餘三種情況下則必須給出相同的答案，然而沒有辦法交流得知到底屬於哪一種情況。因此，假如不動用量子糾纏的力量，Alice 和 Bob 的最佳策略很簡單，就是在玩遊戲前就說好，待會無論如何兩人都回覆一樣的答案。勝率是 75%，不能再高。

假如使用量子糾纏的力量呢？Alice 和 Bob 可以建構出具有如下狀態的一對糾纏粒子：

這對粒子，只要兩邊沿著同一個方向測量（本例的測量方向都在同一個平面上），不管誰先測、測出什麼，兩邊的測量結果必定相同。

Alice 和 Bob 談好了如下策略：

• 各自選擇兩個測量方向，先以變數表示：Alice 的是 、，Bob 的則是 、。

• 遊戲進行時：

  • Alice 如果收到隨機位元 ，就沿著 方向量測糾纏粒子，測量結果為 ；收到 則沿著 方向測量，測量結果為 。

  • Bob 收到 就沿著 方向測量，結果為 ；收到 則沿著 方向測量，結果為 。

• 測量結果只能是 +1 或 -1，同 CHSH 測試。

• Alice 和 Bob 各自將測量結果作為答覆，交給裁判。

為了最大化勝率，、、、 應該要是哪些方向呢？遊戲規則告訴我們，當 時，Alice 和 Bob 的答覆必須相異才能獲勝，也就是 的結果必須是負值。因此，Alice 和 Bob 等於是要最大化下列的統計值：

這不就是 CHSH 不等式的左邊嗎！

略過推導（牽涉到超出本文範圍的波函數基底投影機制），為了最大化勝率，Alice 和 Bob 可以採取如下測量方向：

• A1 = 0°

• A2 = 90°

• B1 = 45°

• B2 = -45°

如此一來，最大勝率將提升為 ，大於不使用糾纏粒子的最大勝率 0.75。

要注意的是，在遊戲過程中，Alice 和 Bob 會各自測量持有的糾纏粒子，而測量行為會將這些粒子「消耗掉」，測量之後的它們不再糾纏。

「消耗」這個角度暗示我們，糾纏的粒子們可以被視為一種「工程資源」，用來無視距離的對量子態進行操作。

量子遙傳電路（quantum teleportation circuit）

能否透過消耗掉一對糾纏的粒子，把一筆量子資訊從甲地傳送到乙地？

首先澄清，就算用上了量子糾纏，我們也無法實現超光速的古典資訊傳遞。然而，我們可以藉由消耗一對糾纏的粒子，將 Alice 手上的量子態傳送到 Bob 手上，並且理論上能在乙地完美保持量子態原貌。

基本上牽涉到 5 個步驟：

1. 製備一對糾纏的粒子 a 和 b，狀態處於所謂的 Bell 態（Bell state）：。這對粒子不論誰先被測、測出什麼結果，兩邊測量結果必定相同，都是 0 或者都是 1，並且兩種情況機率相等。

2. 將 a 分配給甲方，將 b 分配給乙方，並且 a 和 b 保持糾纏狀態。

3. 甲方將手上的粒子，和作為訊息的量子態 m，進行糾纏。至此，a、b、m 三個量子態都糾纏在一起。

4. 甲方對 a 和 m 進行測量，因而消耗掉 a，也把 m 塌縮掉。

5. 甲方將測量結果，以古典通訊方法（例如 WhatsApp）告訴乙方。乙方依照得知的資訊，對手上的 b 進行對應的量子閘操作。操作完之後，乙方手上擁有量子態 m。

以量子電路表示如下（量子閘符號，例如 H 閘、X 閘、Z 閘等，超出本文範圍，不做解釋； 代表的 CNOT 閘於下文解釋）：

量子運算的擴容挑戰

關注量子運算的擴容問題，一個最基本的衡量依據是物理量子位元數（physical qubit count），也就是一個運算平台在物理層級上能夠同時製備、維護、操作的量子位元（qubit）實體數量。

過去三十年以來，單一平台（monolithic platform）上的量子位元數量持續的提升，近年來尤以中性原子平台的擴容速度最快，見下圖。

然而，在能夠彈性配置資源來進行單量子位元閘（1-qubit gate）以及雙量子位元閘（2-qubit gate）的前提下，今日的平台極限大約在三位數的物理量子位元。例如：

• Logical computation demonstrated with a neutral atom quantum processor 的 256 顆。

• Logical quantum processor based on reconfigurable atom arrays 的 280 顆。

橫跨不同量子位元類型，要持續在「單一平台」上提升量子位元數量，都遇到困難：

超導電路平台

超導電路平台，以低溫下的超導電路作為量子位元，使用電路的兩個最低能階作為 ，能階差距約為 20 µeV，以 換算成激發頻率約為 5 GHz。因此，在兩個能階之間轉換有賴 5GHz 的微波訊號。

然而，5GHz 的訊號，在波導裡對應的波長大約是 3 公分，和整個電路系統的尺度在同一個數量級，導致顯著的串音（crosstalk）：原本要驅動某特定量子位元的訊號，外溢出去影響其他量子位元。實務上，會透過元件尺寸差異，讓相鄰的量子位元激發頻率錯開。但是這個設計遇到的侷限之一，在於如果甲乙量子位元相鄰，讓甲的激發頻率小於乙，則甲的 激發頻率可能會在乙的 附近，因此當驅動甲的訊號外溢到乙，可能把乙推到 ，超出 的範圍，導致資訊丟失。這導致在單位頻寬內能夠容納的激發頻率數量有限。

更何況，整個超導電路系統的操作溫度通常在 0.015K 左右，必須放置在特製的冰箱裡；越多量子位元，導致需要越多的控制訊號線和讀取訊號線拉進冰箱，導致熱量的帶入、雜訊的增加，而雜訊會摧毀量子態。

離子阱平台

離子阱平台，以都卜勒冷卻（Doppler cooling）和邊帶冷卻（sideband cooling）等手法將離子冷卻到低溫，束縛在由交流電場（Paul 阱，例如 Cirac & Zoller 1995、Monroe et al. 1995）或者靜電場加上強磁場（Penning 阱，例如 Jain et al. 2018）所構成的位能阱裡，形成一顆顆獨立的量子位元。這些量子位元除了各自的量子態，在共享的電磁場裡會形成集體振動模式。正是透過將量子態耦合到這個集體模式，讓量子位元們可以進行量子糾纏，進而進行雙量子位元閘的運算。

然而，一旦量子位元數量上升，集體振動模式就會變得複雜、模式頻率之間的差距變小，容易產生錯誤耦合、引發錯誤的計算。因此，人們不得不放棄製造一個大陷阱、讓所有量子位元都在其中集體振動，改為製造多個獨立的小陷阱。這樣的作法導致必須能夠跨陷阱的搬運離子，增加架構複雜度，並且搬運途中也會產生雜訊，干擾量子態。

中性原子平台

中性原子平台，將以磁光陷阱和邊帶冷卻等手法冷卻到低溫的中性原子，以一顆原子搭配一道光鑷子的方式，束縛在空間中特定位置，形成矩陣排列的量子位元。

要提高量子位元數量，就要將控制這些量子位元的光學系統規模化，也就是能夠同時操作大量的光鑷子、激發和讀取用的雷射光束，同時維持高精度的頻率、相位、空間定位。

另外，在完成冷卻後，需將中性原子以光鑷子重排成規律的矩陣，量子位元越多，重排耗時越長、搬運距離越遠，導致雜訊提高。

為了創造量子糾纏，中性原子被激發至高激發的 Rydberg 態（Rydberg state），透過凡得瓦力，抑制鄰近中性原子被激發到高激發態的能力，這樣的機制導致相鄰的量子位元產生糾纏。然而，量子位元越多、密度越高，凡得瓦力越容易影響到不應被影響的鄰居，導致閘運算的錯誤。

若只提高量子位元數量，不提高密度，導致整體陣列尺寸變大，導致重排、原子搬運的距離和時間提高，雜訊增加。

量子超級電腦

考慮古典電腦的演化史。由於複雜的科學模擬問題超過單一機器的能力，1980-1990 年代興起的大規模平行處理（massively parallel processing），例如 Cray 的超級電腦，將多達兩千顆的處理器聯合在一起。

今日的量子運算，仍處於極早期的階段：尚未有任何單一量子機器能提供古典電腦無法提供的商業應用價值。為了加速擴容，研究者開始問：能否像古典超級電腦那樣，把多個小量子平台連接起來，建造量子超級電腦？

這項任務，面臨不存在於古典超級電腦的挑戰：量子態無法被複製，並且因為容易損耗而無法任意搬移。最好能讓多個量子平台共享量子態、跨平台操作這些量子態，整個過程中盡可能避免去搬運實體量子位元。最好能藉此將多個量子平台「虛擬化」成一個超大型量子平台，擁有等效的大量量子位元，解鎖超過任何古典電腦能力的新運算問題。

非局域門

其中的關鍵之一，就是應用量子糾纏的超距作用力。利用這種力量，我們可以實現「超距門」，更普及的說法是「非局域門」。考慮古典電腦，一個邏輯閘在晶片上的特定位置，佔據特定面積，透過閘的材料使用、結構設計等因素，讓輸入和輸出訊號形成我們需要的邏輯關係。例如，假如我們要將兩個古典位元進行 XOR 運算（），那麼我們得將這兩個位元的訊號傳送到位於電路系統裡「某一個地方」的 XOR 邏輯閘電路的輸入端，在其輸出端得到答案。非局域門，則是能夠無視距離的針對分處異地的多個輸入訊號執行邏輯操作。這就好比，在 101 號實驗室的一號量子平台有一個量子位元 a，其量子態為 x；在隔壁 102 號實驗室的二號量子平台有一個量子位元 b，其量子態為 y，透過非局域門，我們可以在不搬運 a 和 b 的情形下，隔空「打一個響指」，讓 b 的量子態變成 ，代價是消耗一對預先共享的糾纏粒子，並且雙向各傳送一個古典位元。

以這篇論文（Optimal local implementation of non-local quantum gates）的 Remote CNOT 為例進行說明。CNOT 是一種雙量子位元的量子邏輯閘，全名是受控反閘（controlled-NOT）。它有兩個輸入：控制輸入（control in）和目標輸入（target in）；兩個輸出：控制輸出（control out）和目標輸出（target out）。CNOT 的運作規則很簡單：控制輸入是 1 時，目標輸入反轉後成為目標輸出；否則目標輸出等於目標輸入。CNOT 是最基本的邏輯閘之一，搭配單量子位元閘，就能組成通用閘集（universal gate set），角色類似古典運算的 {NAND}。

一般的 CNOT 運作在物理空間中相鄰（局域）的兩個量子位元。Remote CNOT 則超越局域性：

• Alice 和 Bob 分隔兩地，各有一個量子位元 a 和 b。

• 另外，Alice 和 Bob 各持有一對量子糾纏的量子位元之一 和 。

• 透過 Remote CNOT，Alice 和 Bob 可以對 a 和 b 執行邏輯上的 CNOT：以 a 為控制位元、b 為目標位元，若 a 是 0，則 b 保持不變；若 a 是 1，則 b 反轉。

看電路：

一共六個步驟：

1. 製備一對處於 Bell 態的糾纏粒子 ，兩個粒子分別稱作 。

2. 將 「分配」給 Alice 和 Bob（如何「分配」而不牽涉搬運實體量子位元，下文討論）。

3. Alice 將手上的量子位元 a 和 進行糾纏。

4. Alice 測量 （因此將其消耗掉），並將測量結果以古典通訊方法告訴 Bob，Bob 以其為控制位元對 執行一個 CNOT 作為本地修正。

5. Bob 將手上的量子位元 b 和 進行糾纏。

6. Bob 測量 （因此將其消耗掉），並將測量結果以古典通訊方法告訴 Alice，Alice 以其為控制位元對 a 執行一個受控 Z 閘（controlled-Z，CZ）作為本地修正。

結束上述步驟後，Alice 與 Bob 手上的量子位元，經歷了「等效於局域 CNOT」的聯合狀態轉換：

盤點這個程序消耗的資源：

• 1 個糾纏位元（ebit）

• 兩個方向的通訊，各 1 個古典位元（cbit）

總體而言，「預先共享的糾纏」是一種可消耗的資源：藉由消耗糾纏 → 交換古典測量結果 → 施加局域的修正操作，我們可以讓相隔兩地的量子位元共同執行邏輯閘，整個過程中不需要搬運實體量子位元。

4. 商業野心

糾纏互換（entanglement swapping）

注意：上述的量子遙傳電路和非局域門，步驟 1 和 2 都是「製備一對糾纏粒子；將糾纏粒子分配給兩方」。問題是，如何「分配」這些糾纏粒子而不牽涉到搬運脆弱的實體量子位元呢？

事實上，「分配」這個說法並不準確。 並不是在某地製備好之後「分配」給 Alice 和 Bob 的。

實務作法是：用光子作為「飛行量子位元」，將 Alice 和 Bob 手上本來就有的一對量子位元轉變為糾纏態。

更具體一點，中性原子和離子阱平台，使用如下方法製備糾纏資源：

1. Alice 和 Bob 兩方各準備好一個量子位元，用於製備糾纏資源，記作 。

2. 重複下述步驟直到成功：

   1. Alice 和 Bob 各自「激發」手上的量子位元，使其輻射出光子 。 處於糾纏態， 也處於糾纏態。具體「激發」的作法，於下文討論。

   2. 對任何一方而言，成功糾纏後，這個「量子位元-光子」系統狀態可以如此表示：。這代表，該系統有 1/2 機率會量測到「量子位元 0、光子水平（Horizontal）偏振」，另外 1/2 機率則量測到「量子位元 1、光子垂直（Vertical）偏振」。

   3. 將兩顆光子 送到一個中間站。在這裡，我們嘗試對兩顆光子動點手腳，讓分隔兩地的 、 變為糾纏態。作法包含兩個步驟：

      1. 將兩顆光子送入「兩個輸入、兩個輸出」的分光器，讓輸出端的兩顆光子無法分辨是從哪個輸入過來的（功能上類似加密貨幣的混幣器），因而可將兩顆光子視為一個整體。

      2. 去量測這兩顆光子的偏振方向。這個量測程序被稱為 Bell 態量測（Bell state measurement，BSM）。當量測結果顯示特定偏振方向組合時，我們可以宣告（herald） 已經成功進入糾纏態。如果沒有成功，回到步驟 2a 重來，直到這一步成功為止。

這樣的作法，將「 糾纏、 糾纏」轉為「 糾纏」，在 1993 年被提出，稱為「糾纏互換」。

拼圖還缺一個角落：Alice 和 Bob 兩方在步驟 2a，如何讓量子位元和光子產生糾纏呢？

量子位元-光子介面

要如何「激發」一個量子位元 Q，使其輻射出的光子 P 和 Q 處於糾纏態呢？

在自由空間中，有一個中性原子或者離子的量子位元 Q，以雷射脈衝激發 Q，然後它衰變、輻射出一顆光子 P。如果激發後的 Q，有多個衰變路徑可以「選擇」，那麼輻射後 Q 的能階，和 P 的狀態（例如 P 的偏振方向），就可能形成糾纏。但是且慢，在自由空間中做這件事情，有許多變數：

1. 激發後的 Q 會衰變到哪一個能階、輻射出何種頻率的 P 呢？

2. 激發後的 Q 朝哪一個方向輻射出 P？

3. 從激發到輻射之間的時間多長？

關於變數 1，請注意，我們希望輻射後的 Q 是回到 或者 這兩個能階的其中之一。一個具體的量子平台，使用特定元素、在特定外加磁場下的中性原子或者離子，會有特定的 ，作為計算子空間。計算子空間，以古典運算類比，好比 CMOS 晶片上的 0 伏特電位，和 1.2 伏特電位，前者解讀為邏輯 0，後者解讀為邏輯 1。要是輻射後的 Q 跑到 之外，那就構成計算子空間的「洩漏」（leakage），如果無法補救、映射回子空間，就丟失了資訊。

關於變數 2，在自由空間中輻射可能朝各種方向隨機。當方向不可控，導致收集光子的效率低下。

關於變數 3，在自由空間中輻射的時間，也是隨機的，具體而言，衰變等待的時間呈指數分佈。相較之下，空腔能縮短並塑形光子的波包，讓兩地的光子更容易在分光器上重疊，重複速率也更高。

為了讓衰變路徑、輻射方向和時間可控，研究者使用空腔來改變量子位元周圍的電磁場環境。關鍵物理機制是 Purcell 效應（Purcell effect）。1946 年，研究核磁共振的 Edward Purcell，在一篇簡短會議摘要中提出，一個輻射體，如果位於一個空腔中，空腔的共振模式與輻射體的頻率共振，可以提高輻射體的輻射速率。這種由空腔引起的自發輻射速率改變，稱為 Purcell 效應。

把空腔做成兩面相對的鏡子，透過設計這個空腔的幾何形狀，然後把量子位元擺在空腔中適合的位置，進行激發和輻射，可以提高對上述三種變數的控制。如果其中一面鏡子的透射率高一點，可以作為「輸出鏡」，讓 Q 輻射出來的光子跑出來、送進光纖裡，帶往中間站。2007 年這篇論文（Single-Atom Single-Photon Quantum Interface）是實現上述設計的早期代表性論文之一。

Nu Quantum 的野心：資料中心級的分散式量子運算

Nu Quantum 是一間於 2018 年從劍橋大學卡文迪許實驗室（Cavendish Laboratory）衍生出的英國公司，致力於成為服務未來量子電腦資料中心的「Cisco」，提供量子電腦連線、共同運算的網路層解決方案。

Nu Quantum 正是使用空腔作為量子位元-光子介面（qubit–photon interface，QPI）。下圖出自 Nu Quantum 的 PCT 專利申請 WO2023073379A1；同一專利族的英國專利 GB2612578B 已於 2024 年獲准。

針對圖中主要元件進行說明：

• 104a 和 104b 就是構成空腔的兩面鏡子。

• 112 是量子位元。

• 106 是空腔本身（104a 與 104b 之間的空間）；用以激發量子位元的雷射脈衝，則沿圖中右側的虛線箭頭從側面打入。

• 左側的 114 是機械致動器，使用 PDH 穩頻技術，配合 102 和 108 這兩面鏡子（104a 和 104b 的延伸），透過反饋機制鎖定鏡子之間的距離，動態的保持空腔共振模式的頻率穩定。

根據 2025 年發表的論文（Optical Microcavities for Efficient Qubit-Photon Interfaces and Networked Quantum Computing），空腔長度約為 370 微米、腰部寬度約為 5 微米。2024 年的新聞稿則揭露空腔長度可以鎖定在 0.08 奈米以內，以常見的中性原子量子位元 Rb-87 躍遷波長 780 奈米而言，對應的頻率誤差約為 （約 80 MHz）。

2024 年 O’Reilly et al.（Monroe 團隊）這篇論文（Fast photon-mediated entanglement of continuously-cooled trapped ions for quantum networking）堪稱目前最先進的成果，做到每秒創造 250 次（250 Hz）成功糾纏的頻率。由於「量子超級電腦」需要糾纏資源來執行非局域門，製造糾纏資源的頻率至關重要。Nu Quantum 的短期目標之一是將該頻率再提高兩個數量級。

Nu Quantum 的宏觀目標是在一個資料中心尺度的屋簷下，將多個量子平台（又稱為量子處理器，即 quantum processing unit，簡稱 QPU；目前僅接受離子阱與中性原子平台）虛擬化為單一分散式平台。解決方案一共分為三層：

1. QPI 為最底層，安裝在各量子平台中，負責創造上述的量子位元-光子糾纏，輸出光子。

2. 往上一層是量子網路單元（Quantum Networking Unit，QNU），將來自各 QPI 的光子進行路由、配對、重複執行 BSM 程序直到宣告成功，負責為任意一對 QPU 創造共享非局域糾纏資源。

3. 再往上一層為分散式量子糾錯（Distributed Quantum Error Correction，DQEC；2025 年的論文），負責橫跨 QPU 執行錯誤偵測和修正，使得所有 QPU 的物理量子位元能夠抽象化為一定數量的邏輯量子位元（logical qubit），供量子軟體使用。

CavilinQ 的野心：高速量子互聯

新創公司 CavilinQ 成立於 2025 年，同樣致力於以光子互聯來擴容量子電腦的長期願景。重點在於提高 QPI 的操作頻率和保真度，用來高速生產量子平台間的非局域糾纏資源。

CavilinQ 研發出的空腔，能更快的發射光子，其光子具有更高的方向性和發射時間精度，進而加速後續的宣告步驟。另外，團隊具備將五種以上不同空腔整合進量子記憶體的經驗，這樣的實作經驗是在現實世界部署量子互聯所必需的。

回顧 QPI 的運作關鍵，在於讓空腔共振模式的頻率，盡可能接近量子位元目標衰變躍遷的頻率；兩者越接近，就有越高的機率誘導量子位元做出所需的衰變。一個關鍵指標是空腔的精細度（finesse，一般記作 ，是沒有單位的比值）。提高精細度（降低腔內損耗）並縮小光腰，可以提高量子位元與腔模的耦合，讓更多光子進入腔模、再經輸出鏡取出。

團隊發表的最新論文（High Finesse Buckled Microcavities）揭露一種新的空腔製程，在 780 奈米的波長上，精細度達到約 90 萬。簡述製程如下：

1. 將一片矽晶圓的表面進行平滑化處理。

2. 用離子束濺鍍技術，在矽晶圓的一面上鍍膜，結構為數十層高低折射率材料交替堆疊，在目標頻率區間創造高反射率。

3. 將矽晶圓翻過來，塗布光阻，進行矽蝕刻。光阻圖案開口區域的矽基板被貫穿，露出鍍膜的背面。鍍膜懸空後，內部應力導致鍍膜彎曲成凹面鏡。

4. 將光阻洗掉。單獨的鏡面晶片在步驟 3 的蝕刻中就已從晶圓上分離，不需要切割。將兩片凹面鏡相對黏合，形成空腔。

除了量子運算擴容外，團隊盼望其量子互聯技術能推動以下應用：

盲量子運算

盲量子運算的概念早在 2001 年就被提出（Childs，Secure assisted quantum computation，2005 年正式刊登）。伺服器對計算內容一無所知的特性，稱為「盲性」（blindness）。

設想：

• Alice 有寶貴的量子態 、寶貴的量子演算法 ，以及有限的量子運算資源（有量子記憶體、可以執行簡單的 Pauli 閘）。

• Bob 則有意出租其通用型量子電腦。

盲量子運算的協定，讓 Bob 能作為 Alice 的代理，執行 、交付答案，過程中 Bob 無法得到任何有關 或是 的資訊。

2008 年提出的 BFK 協定（Universal blind quantum computation，2009 年發表）讓客戶端不再需要量子記憶體或量子閘，只要準備隨機的單一量子位元送給伺服器，就能盲執行任意量子演算法。2016 年 Takeuchi et al.（Fault-tolerant verifiable blind quantum computing with logical state remote preparation）基於 BFK 協定，在理論上加強容錯性，讓伺服器端可以執行更長的運算時間、承受更大的雜訊，依然給出正確運算結果。

2025 年 Baranes et al.（Designing fault-tolerant blind quantum computation）設計出可擴展到容錯規模的架構，同時讓客戶端的需求維持在極低的程度：

• 客戶端只需要具備「針對來自伺服器的光子量子位元，在任意基底（方向）上進行測量」的能力即可，既不需要保存量子態，也不需要執行任何閘。

• 伺服器端仰賴 QPI，在協定中反覆將物質量子位元與光子耦合、將這些承載量子資訊的光子送到客戶端進行測量。

這樣的技術降低盲量子運算的客戶端成本、擴大這項技術的潛在市場。

量子超長基線干涉技術

量子互聯技術可應用於宇宙觀測。具體概念是，透過量子糾纏的非局域的特性，將天文干涉儀的基線做得更長來提高解析度，並透過避免傳輸天文光子來提升靈敏度。

先針對幾個著名的天文干涉儀系統，進行簡短介紹。

1. 事件視界望遠鏡（Event Horizon Telescope，EHT），於 2000 年代初期開始概念性試驗，2009 年計畫發起，2017 年達到可正式觀測的規模。利用的技術稱為「特長基線干涉測量法」（very long baseline interferometry，VLBI）：先將分佈各地的望遠鏡以原子鐘進行精確時間同步，然後同時觀測同一個遙遠天體發出的電波，各自將電波的相位資訊記錄在時間同步的電訊號中，所有電訊號集中至相關器中心執行時間校正和干涉計算，產生干涉條紋，進而重建天體影像。人類史上第一張黑洞影像就是由 EHT 捕捉到的。2017 年 4 月全球 8 座望遠鏡同時按下快門，在大約 40 個小時的曝光時間內搜集約 3.5PB 的數據，2019 年 4 月完成數據處理，公布影像。EHT 操作波長約 1.3 毫米（230 GHz），即微波頻段，受到原子鐘的極限以及大氣層水氣干擾問題所侷限，觀測頻率難以進一步提升。角解析度達到 20 微角秒，相當於能從地球分辨出月球表面上的乒乓球。

2. 海軍精密光學干涉儀（Navy Precision Optical Interferometer，NPOI），1994 年建成，陣列呈 Y 字形，三條臂各長 250 公尺，定天鏡（siderostat）可以搬到臂上不同的觀測墩（pier），藉此調整基線長度，進而影響解析度。來自星星的光線走真空金屬管道，搭配調整光路長度用的延遲線，讓各站搜集到的微弱星光同時抵達中間的干涉站進行干涉。設計上的最大基線達 437 公尺，對應約 0.2-0.4 毫角秒的理論角解析度；操作頻段是比微波還要更高頻的可見光，操作波長約 450-850nm。相比之下，哈伯望遠鏡對可見光的角解析度約 50 毫角秒。

3. 高角解析度天文中心（Center for High Angular Resolution Astronomy，CHARA），1999 年首次取得干涉條紋，2000 年落成啟用。最大基線 331 公尺，操作頻段是可見光和近紅外光，波長 500-2500nm，對應的角解析度約 0.3-1.5 毫角秒（隨波長而定）。和 NPOI 一樣採用的是微弱星光從各望遠鏡走真空金屬管道抵達干涉站進行干涉的作法。系統一共包含六座望遠鏡，兩兩配對可提供 15 種不同的基線長度選擇。

NPOI 和 CHARA 的限制在於，若要進一步提高解析度，則必須把基線變長，加劇微弱星光在管道中的衰減與相位擾動。若改用無線電 VLBI 的作法，在各站以本地振盪器各自量測，又會引入零點漲落造成的真空雜訊，對微弱的星光而言靈敏度太差。

有沒有辦法讓抵達不同觀測站的星光進行干涉，而不必在地表上傳輸微弱的星光？

有辦法：執行非局域干涉。

理論構想最初約在 2011 年由 Gottesman et al.（Longer-Baseline Telescopes Using Quantum Repeaters）提出，同年 Mankei Tsang（Quantum Nonlocality in Weak-Thermal-Light Interferometry）證明在弱光條件下，把兩站光場放在一起量測的「非局域」方法，在測量精確度上嚴格優於兩站各自量測、再合併結果的「局域」方法（例如無線電 VLBI 的外差偵測）。

到了 2025 年，Stas et al.（Entanglement assisted non-local optical interferometry in a quantum network）以實驗室的弱雷射脈衝模擬星光，驗證了非局域干涉望遠鏡的概念：兩站實際相距約 6 公尺，在兩站之間加入光纖捲後，有效基線延長到 1.55 公里。具體作法如下：

1. 兩處觀測站各有量子記憶體，記憶體內含一個記憶用的量子位元，以及一個通訊用的量子位元。稱記憶用量子位元為 、，通訊用量子位元為 、。

2. 為兩處觀測站準備好一個異向疊加的糾纏對 ，將糾纏態存在記憶用量子位元 ，延長保存時間。

3. 星光隨時可能以疊加態的形式，同時抵達兩個觀測站，稱其為天文光子。

4. 當天文光子抵達時，有一定機率和兩站各自的量子記憶體裡的通訊用量子位元產生耦合，進而將光子資訊寫入 、。

5. 將天文光子導出，在分光器上和本地振盪器送出的弱同調光脈衝混光（其光子數本身就不確定），藉以抹除「觀察到天文光子具體抵達哪一個觀測站」的可能性，確保維持其疊加態。

6. 兩站的量子記憶體，分別針對內部兩個量子位元執行一個 CNOT（以記憶用量子位元為控制位元）。記得 在一開始已經處於糾纏態。至此，若 、 攜帶天文光子資訊，該資訊已耦合進 。

7. 分別測量 、 的自旋方向。如果測出同向，則我們確知天文光子資訊有被系統捕獲。若測出異向，則系統沒有捕獲天文光子。

8. 若有捕獲天文光子，此時系統波函數為 ，正負號取決於前一步 、 是測出上還是下， 則為我們真正在乎的天文光子疊加態在兩站之間的相位資訊。

9. 測量此系統波函數。

10. 執行上述步驟 2-9 多次，在有捕獲天文光子的前提下（由第 7 步判斷），反覆測量最後的系統波函數，透過統計方法可估計出 的數值。

有了天文光子的相位資訊，搭配基線長度等系統資訊，就可以反推天體的位置以及還原出天體影像。

遙想有朝一日能夠建造像是 VLBI 那樣分佈全球地表的非局域干涉觀測站網路。若要更長的基線，並消除大氣水氣干擾，可以架設人造衛星網路來承載這個系統，允許人類更進一步探究璀璨星空的奧秘。

This essay is by Thomas Hsueh (X: @guiltygyoza). He founded Topology, and his research has spanned crypto-native games, autonomous worlds and verifiable computing. Since 2025 he has turned to the applied sciences, and lately to research on quantum computers and AI. His blog is guiltygyoza.xyz.

This essay was first published on the Parity website; this newsletter edition is a reprint. There is also a Chinese edition. Telescope Editions is Parity’s research grant program.

1. Causal Locality & Cellular Automata

In this world, nothing—tangible or intangible, atoms or bits—can move faster than light, right?

We live in an era where special relativity has been verified. We believe in causality: an effect must occur after its cause. We believe that the transmission speed of any causal effect cannot exceed the speed of light in vacuum. We are familiar with Minkowski diagrams and understand that a cause must lie within the past light cone of its effect. Causal effects propagate at a finite speed and cannot ignore the distances in between. This mental model can be called “causal locality.”

The mental model of “causal locality” is so widespread that, in the field of computer science, Leslie Lamport defined the “happened-before relation” (), on which later researchers (Ahamad et al. 1995) built “causal consistency” for distributed systems: given a system with many processes, and given any two operations and satisfying , if every process in the system is guaranteed to observe before observing , then the system is “causally consistent.” In such a system, all processes observe the same causal order.

We can study “causal locality” from a computer science perspective: cellular automata. Design a cellular automaton with the following rules:

• On a two-dimensional plane, there are two large balls, one on the left and one on the right.

• At every time step, the left ball and the right ball each toss a coin with a 50-50 probability to determine what color they will be in the next time step.

• Once a ball is “measured,” that ball freezes in its color at the moment of measurement and emits a particle toward the other ball. The particle carries the color of the frozen ball.

• A ball hit by a particle freezes into that color and absorbs the particle.

Start this cellular automaton, and measure the right ball after some time. You may observe the following result:

You will find the left ball’s color has two states:

1. State 1: after the right ball is measured, and before the particle reaches the left ball, the left ball’s color is randomly red or blue with a 50-50 probability.

2. State 2: after the particle hits the left ball, the left ball must have the same color as the right ball.

In short, after the right ball is measured, the color of the left ball is a function of the particle’s speed.

In this cellular automaton, all rules are defined over adjacent cells—each cell has eight neighbors, known as the Moore neighborhood. This limitation forces the cellular automaton to obey “causal locality,” because all changes can only be transmitted through neighboring cells. The speed of the particle is exactly “one cell per time step.” This speed is the “speed of light in vacuum” of this tiny cellular-automaton universe.

If we allow the particle to move faster, then we will be more likely to measure the left and right balls as having the same color.

Now, use our imagination to consider the case where the “time step is infinitesimally small”: the two balls randomly flash between red and blue “infinitely fast,” while the particle also moves “infinitely fast.”

Reconsidering the above experiment, we find that state 1 disappears, leaving only state 2. Using Dirac notation, let red be represented by and blue by . When the time step is infinitesimally small, the measurement statistics of the two balls’ colors match those of the following quantum state:

This expression says: there is a one-half probability that we will measure both balls as red, and another one-half probability that we will measure both balls as blue.

The particle moves at an “infinite speed,” causing the causal effect to violate locality and propagate at an infinite speed. This thought experiment uses a cellular automaton to demonstrate the effect of “quantum entanglement.”

Measuring one ball (cause) causes the other ball to “immediately” freeze into the same color (effect). This instantaneous propagation of causal effects regardless of distance was called “spooky action at a distance” by Einstein.

2. The Spooky Force That Worried Einstein

Local Realism

Shohei Ohtani’s splitter travels like a fastball, but drops rapidly before reaching home plate, landing in the lower-right corner of the strike zone, once again baiting the batter to swing and miss.

Is it possible to accurately calculate where a splitter will land? Common sense tells us that, by carefully considering more factors and making no computational errors, we can approach arbitrary accuracy in our result. First, consider the velocity vector of the baseball at the instant it leaves Shohei’s hand. Next, consider the angular velocity vector of the baseball at that same instant. If necessary, at every moment during the flight, consider factors such as the gravitational field, wind direction, air pressure, and humidity at its location. Consider using the most precise computer and the smallest mesh to run the most accurate finite element simulation. We believe that, by considering more factors and maintaining computational rigor, we can approach the truth.

A necessary corollary of this belief is the following: if the calculation result deviates from the truth, and we are certain that no computational error has been made, then there must be some factors that should have been considered but were missed.

Expressed in more abstract language, this belief is “realism”: everything in the universe is objectively real. If we observe a system and obtain an observation result , it is because, before the act of observation, “already” possessed a real and definite state, and our act of observation produced the result .

Imagine a simple side-scrolling game. As the player, you are located somewhere on the map. Your field of view is limited, as you can only see nearby features, such as a few walking mushrooms. However, in the background, the game system tirelessly calculates the behavior of everything on the map, regardless of whether those things appear within your field of view. This is a manifestation of “realism.”

Applied at the scale of the universe, “realism” tells us that, whether or not it is observed by a conscious subject, every location in the universe, at every moment, evolves perfectly and faithfully according to the laws of the universe.

Cunning game designers, seeking to create rich game experiences on computing platforms with limited capabilities, abandoned “realism” long ago. Super Mario Bros., released by Nintendo in 1985, does not obey “realism.” The player’s field of view is called the visible screen, while a slightly larger area is called the relevant screen. Only the game map within the relevant screen is attended to by the game system and updated frame by frame. Outside that area, monsters have not yet been born, and objects remain frozen in their “initial states.” The practice of “do not calculate what the player cannot observe” can significantly save memory and computation while having no significant effect on the gameplay experience.

However, we fundamentally do not believe that the universe plays this trick, behaving arbitrarily in places that are not being observed. We fundamentally believe that everything in the universe evolves tirelessly with perfect precision, like perfectly interlocking gears.

Combining “realism” with “causal locality” gives us the well-known idea of “local realism”: everything that exists is objective and independent of any observation, and an event occurring in one region cannot influence another region faster than the speed of light.

If you currently hold this belief and regard it as self-evident, then you are practically one hundred years out of date. A century ago, this belief was challenged by quantum mechanics.

Challenge to Realism

In the spring of 1925, the Davisson–Germer experiment discovered that the electron-scattering phenomenon it had originally set out to investigate—which you can understand as a microscopic billiards experiment—displayed a scattering distribution far more complex than expected.

In 1926, Davisson and Germer learned of the quantum-mechanical theories of de Broglie and Schrödinger, which argued that electrons possess wave-like properties, and were encouraged by Max Born to investigate the phenomenon as wave diffraction rather than particle scattering.

In the spring of 1927, they published their experimental results: electrons scattered off the surface of a nickel crystal came back strongly only at particular angles, exactly as waves diffracted by the crystal lattice would.

The fact that particles possess wave-like properties is itself a challenge to realism. A particle, at any given moment, can only actually exist in one place, right? Semantically, a particle is a localized existence. Quantum mechanics, however, says that a particle’s position does not possess one single, definite existence. Instead, it is probabilistically spread across space and described by wave theory.

In October 1927, at the star-studded Fifth Solvay Conference in Brussels, with the theme “Electrons and Photons,” Einstein and Bohr debated whether quantum mechanics could completely describe all behavior in the universe. Einstein believed it could not; Bohr believed it could. In response to the electron-diffraction experiment, Einstein proposed a thought experiment:

• Prepare a system consisting of an electron gun, a slit, and an imaging screen.

• Quantum mechanics claims that the universe can tell us only “the probability that, after passing through the slit, the electron will appear at a particular location on the screen.” Einstein believed that this inability to provide an exact position, and its ability to provide only probabilities, resulted from some factors that should have been considered but were missed. Recall our earlier discussion of where Shohei Ohtani’s splitter would land.

• If we carefully observe tiny changes in the slit while the electron is passing through—for example, the slight recoil of the slit when the electron strikes it—we can obtain more information beyond the limits of quantum mechanics, which would help us infer the electron’s trajectory. Recall our earlier discussion about wind direction, air pressure, and humidity.

Bohr replied that if we precisely observe the recoil of the slit—its momentum—then the uncertainty principle of quantum mechanics tells us that we can no longer possess precise information about the slit’s position. Since the diffraction pattern depends on the position of the slit, if the slit’s position becomes uncertain, the diffraction image becomes disordered. The pattern would disappear.

Einstein was not satisfied. He believed that there must be some missing factors. The idea that there could only be “probability” and no certainty had to be a defect in human physics. The universe should not evolve in an uncertain way.

Heisenberg recalled:

• Einstein: “God does not play dice.”

• Bohr: “It cannot be for us to tell God how he is to run the world.”

Challenge to Locality

At the same conference, Einstein proposed another thought experiment:

• Prepare a system consisting of an electron gun, a small aperture, and an imaging screen.

• Quantum mechanics says that after an electron passes through the aperture, it forms a hemispherical “electron wave,” and the electron’s possible location can be described by the shape of this wave. Although the electron wave spreads in every direction, experiments tell us that if the electron gun emits one electron, only one point will appear on the imaging screen.

• If the electron wave is the electron’s physical reality after it passes through the aperture, this reality, taking the shape of a wave and spreading throughout space, eventually becomes a single point upon reaching the screen. This “collapse” from a wave to a point would require some instantaneous method of transmitting information that disregards distance: the point at which the electron is detected must instantly notify every other location on the screen, “Hey, the electron is here! You are not allowed to detect it there!”

• Such a distance-defying force violates locality. It is a “spooky action.”

Quantum mechanics challenges both “realism” and “locality”: things possess no definite reality and can only be described in terms of probability, while a nonlocal action at a distance governs how those probabilities change.

Many years after the conference, Einstein remained dissatisfied. The 1935 EPR paper was an attempt to challenge quantum mechanics. Imagine two particles, and , that interact and then separate: their total momentum is zero, and the distance between them is also definite. We may freely choose whether to measure the momentum or the position of . If we choose to measure the momentum of , by applying conservation of momentum, we can instantly determine the momentum of . If we choose to measure the position of , because the distance between the two is definite, we can instantly determine the position of without measuring it.

Based on this result, if we believe in “locality”—that measuring cannot instantaneously affect —the momentum and position of must each be real and definite. Only then could their values be known instantly without being measured. Finally, because quantum mechanics claims that only one of position and momentum can be described precisely at a time, quantum mechanics must be incomplete: there must be some hidden factors that should have been considered.

Call these hidden factors “hidden variables,” and the resulting theory is called a “local hidden-variable theory” (LHVT).

In 1951, the EPR paper’s thought experiment was reformulated by David Bohm. After two particles that had been bound together separated, conservation of angular momentum meant that measuring the spin value of one particle along a certain axis would reveal the spin value of the other particle along the same axis. Spin values are discrete, , and are easier to measure precisely in experiments than the continuous position and momentum.

In 1964, John Bell turned this thought experiment into a falsifiable inequality, allowing LHVT to be falsified using statistical values from experimental data. In 1969, John Clauser and others removed one strict condition required by Bell’s thought experiment—that measurements along the same direction on the two sides be perfectly anticorrelated, which no real source, analyzer, or detector achieves—and designed a version that was easier to test experimentally, together with a new inequality known as the CHSH inequality.

To date, Bell inequalities (CHSH and its variants) have been violated in several dozen experiments, e.g., Freedman & Clauser 1972, Aspect et al. 1982, Weihs et al. 1998, Hensen et al. 2015.

These experimental results suggest that we abandon our belief in “local realism.” In its place, there exists in the universe an action-at-a-distance force that can transmit causal effects instantaneously. It is precisely this action-at-a-distance force that is responsible for state updates in quantum-entangled systems.

Recall the cellular automaton from earlier. With the particle moving at infinite speed, we could squint and view the two balls as a quantum-entangled system. When the color of one ball is measured, the color of the other ball is frozen into the same color at that very instant.

3. Harnessing the Spooky Action

The CHSH Test and Inequality

Let’s study the CHSH inequality:

Picture Alice and Bob as two experimenters separated in space. Between them is a pair of twin particles bound together. Suddenly, the pair splits apart, and each particle flies toward one of the experimenters. The experimenters are interested in the spin values of these particles, and each chooses 2 directions along which to perform measurements. For example, Alice’s first direction may be the vertical direction perpendicular to the ground, while her second direction may be parallel to the ground to her right-hand side. The two experimenters may freely choose whichever directions they prefer.

Any measured spin value of a particle can only be +1 or -1:

• +1 means “the particle was measured to spin along the measurement direction!”

• -1 means “the particle was measured to spin in the direction opposite to the measurement direction!”

Now let’s formalize our discussion with variables. Alice’s two measurement directions are and . The spin value obtained by measuring along is , while the spin value obtained by measuring along is . Thus,

Bob’s directions are and , and his results are

Alice and Bob perform this experiment many times, independently record their measurement results, and finally run a statistical analysis.

In each experimental run, there are only 4 possible combinations of Alice’s and Bob’s measurement directions:

In each run, the product of Alice’s and Bob’s measurement results takes one of two possible values: .

The left-hand side of the CHSH inequality is this expression:

where denotes the statistical average. What do these averages mean? Take . Across all experimental runs, select those where Alice and Bob used the measurement combination . Calculate the product of their results from each selected run, then take the average.

Therefore, the above expression amounts to calculating four average values from experimental data, adding the first three together, and subtracting the fourth.

If we believe in “local realism,” after the particles separate, they no longer exchange information. Each particle carries its own “real values” toward its respective experimenter. Imagine that when the particle flying toward Bob separates from its twin, it has already “decided”: if Bob measures along direction , I will give him the result +1; if he measures along , I will give him the result -1.

By enumerating all possible “decisions” that the pair of twin particles could make, the authors of the CHSH paper found that “local realism” leads to:

However, to date, several dozen experiments have produced data that violate this inequality.

The CHSH Game

Some researchers are not so much interested in “local realism.” After all, they—or their academic advisors—were already persuaded by Bohr back in the days of the Solvay conferences. Their focus is on quantum information technology: What use does this spooky action have in information technology?

In the early 2000s, the experimental test of the CHSH inequality was reformulated as a cooperative information game:

• Alice and Bob are separated and cannot communicate.

• A neutral referee gives each of them a random bit, with values and , and asks each of them to return one bit to the referee, with values and .

• Alice and Bob win together:

  • If , and must differ.

  • If and take any of the other 3 combinations, and must be the same.

Compress the conditions above into a single equation:

Interestingly, because quantum entanglement does not count as communication, the game allows Alice and Bob to share and operate on a pair of entangled particles. Imagine the two balls from our earlier cellular automaton: Alice and Bob may each hold one of them.

How should Alice and Bob play? Consider the challenge. When , the two must give different answers; in the other three cases, they must give the same answer. However, they have no way to communicate and determine which case they are in. Therefore, without leveraging quantum entanglement, their best strategy is very simple: before the game begins, they agree that no matter what happens, they will both return the same answer. Their winning probability is 75%. It is impossible to get any higher than that.

What if they leverage quantum entanglement? Alice and Bob can prepare a pair of entangled particles in the following state:

For this pair of particles, as long as both sides measure along the same direction (all the directions in this example lie in one plane), no matter who measures first or what result is obtained, the measurement outcomes on the two sides will always agree.

Alice and Bob then agree on the following strategy:

• Each chooses two measurement directions. Alice’s directions are , while Bob’s directions are .

• During the game:

  • If Alice receives the random bit , she measures her entangled particle along direction , obtaining the result . If she receives , she measures along direction , obtaining the result .

  • If Bob receives , he measures along direction , obtaining the result . If he receives , he measures along direction , obtaining the result .

• As in the CHSH test, any measurement result can only be +1 or -1.

• Alice and Bob each submit their measurement result to the referee as their answer.

To maximize the winning probability, what directions should be?

The rules of the game tell us that when , Alice and Bob must give different answers to win. In other words, the product must be negative. Therefore, Alice and Bob are effectively trying to maximize the following statistical quantity:

This is exactly the left-hand side of the CHSH inequality!

Skipping the derivation—which involves wave-function basis projection, beyond the scope of this article—we find that Alice and Bob can choose the following measurement directions to maximize their winning probability:

• A1 = 0°

• A2 = 90°

• B1 = 45°

• B2 = -45°

These choices lead to a winning probability of , or 85.36%, which is greater than the maximum winning probability of 75% when quantum entanglement is not used.

Note that Alice and Bob each measure the entangled particle in their possession. The act of measurement “consumes” the particles: after they are measured, they are no longer entangled.

This notion of consumption suggests that entangled particles can be considered as an engineering resource to perform nonlocal operations on quantum states.

Quantum Teleportation Circuit

A more generalized goal than winning the CHSH game is: how to transfer a piece of quantum information from Alice in one location to Bob in another location using entangled particles?

To clarify, even with quantum entanglement, we cannot achieve faster-than-light transmission of classical information. However, by consuming a pair of entangled particles, we can transfer the quantum state held by Alice to Bob. Notice that after the transfer, Alice no longer possesses the quantum state, as we are confined by the no-cloning theorem.

At a basic level, the transfer involves 5 steps:

1. Prepare a pair of entangled particles, and , in the so-called Bell state. The measurement results on these two particles are either both 0 or both 1, with equal probability.

2. Distribute to Alice, and to Bob, while keeping and entangled.

3. Alice entangles her particle with the message quantum state . At this point, the three quantum states , , and are all entangled together.

4. Alice measures and , thereby consuming as a resource, and collapsing .

5. Alice communicates the measurement results—classical information—to Bob through a classical communication channel. Based on the information received, Bob performs the corresponding quantum gate operations on as a correction. Now, Bob possesses the message quantum state .

The entire process can be represented by the following quantum circuit. Quantum gate symbols such as the gate and the and gates are beyond the scope of this article; the symbol representing the CNOT gate will be explained below.

Scaling Challenges of Quantum Computing

In scaling quantum computers, one of the most basic metrics is the physical qubit count: the number of physical qubits that a computing platform can prepare, maintain, and operate at the physical level.

Over the past thirty years, the number of qubits on a single (monolithic) platform has continued to increase. In recent years, neutral-atom platforms in particular have scaled at the fastest rate, as shown in the figure below.

However, if we require that the physical qubits be flexibly allocatable to perform 1-qubit gates and 2-qubit gates, the limit today is in the hundreds of physical qubits on a single platform. For example:

• 256 qubits in Logical computation demonstrated with a neutral atom quantum processor.

• 280 qubits in Logical quantum processor based on reconfigurable atom arrays.

Across different qubit types, single-platform scaling encounters various difficulties.

Superconducting-Circuit Platforms

Superconducting-circuit platforms operate superconducting circuits at low temperatures as qubits, and use the two lowest energy levels of the circuit as and . The energy gap is commonly around 20 µeV, corresponding to an excitation frequency of approximately 5 GHz. Therefore, transitions between the two energy levels rely on 5 GHz microwave signals.

However, a 5 GHz signal corresponds to a wavelength of approximately 3 centimeters in a waveguide, which is on par with the scale of the entire circuit system, leading to significant crosstalk: a signal originally intended to drive a specific qubit spills over and affects other qubits. In practice, excitation frequencies of neighboring qubits are staggered through deliberate control of circuit dimensions. However, one limitation of this design is that if qubits A and B are adjacent, and A’s excitation frequency is lower than B’s, then A’s frequency may be close to B’s frequency. As a result, when the signal driving A spills over to B, it may push B into , causing information loss. This limits the number of excitation frequencies that can be accommodated within finite bandwidth.

Moreover, the entire superconducting circuit system typically operates at approximately 0.015 K and must be placed inside a specially designed refrigerator. More qubits require more control signal lines and readout signal lines to be routed into the refrigerator, bringing in more heat and increasing noise. Noise destroys quantum states.

Trapped-Ion Platforms

Trapped-ion platforms cool ions to low temperatures using methods such as Doppler cooling and sideband cooling, and confine them in potential wells formed by alternating electric fields (Paul traps, e.g., Cirac & Zoller 1995 and Monroe et al. 1995) or by a static electric field combined with a strong magnetic field (Penning traps, e.g., Jain et al. 2018). Each ion constitutes an individual qubit. In addition to their individual quantum states, these qubits form collective vibrational modes within the shared electromagnetic field. By coupling their quantum states to these collective vibrational modes, the qubits can become entangled for the purpose of performing 2-qubit gate operations.

However, once the number of qubits increases, the collective vibrational modes become more complex, and the modes crowd together, making unintended entanglement more likely and causing errors in computation. Therefore, researchers moved on from building one large trap shared by all qubits to building multiple independent smaller traps. This approach requires the ability to transport ions between traps, increasing architectural complexity. The transport process also generates noise that interferes with the quantum states.

Neutral-Atom Platforms

Neutral-atom platforms cool neutral atoms to low temperatures using methods such as magneto-optical trapping and sideband cooling. Each atom is confined by an optical tweezer at a specific position, forming a matrix of qubits.

Increasing the number of qubits requires scaling up the optical systems that control them: these systems must simultaneously operate large numbers of optical tweezers and laser beams for excitation and readout, while maintaining high precision in frequency, phase, and spatial positioning.

After cooling is completed, the neutral atoms must be rearranged into a matrix with optical tweezers. The more qubits there are, the longer the rearrangement takes and the farther the atoms must be transported, increasing noise.

To create quantum entanglement, neutral atoms are excited into highly excited Rydberg states. Through van der Waals forces, an atom in a Rydberg state suppresses the probability of nearby atoms getting excited to the same state, a mechanism known as the Rydberg blockade, which causes neighboring atoms to become entangled. However, as the number and density of qubits increase, van der Waals forces are more likely to affect nearby atoms that should not be affected, causing gate errors.

If we scale up the number of qubits without increasing density, the overall array becomes larger, increasing the distance and time required for rearrangement and atom transport, thereby increasing noise.

Quantum Supercomputer

Consider the evolution of classical computers. Because complex scientific simulation problems exceeded the capabilities of any single machine, massively parallel processing emerged in the 1980s and 1990s. Supercomputers such as those built by Cray at the time connected as many as two thousand processors together.

Quantum computing today remains at a very early stage: no single quantum machine has yet provided commercial application value that classical computers cannot provide. To accelerate scaling, researchers began to ask: as with classical supercomputers, how can we connect multiple small quantum platforms to build a quantum supercomputer?

This mission involves challenges that do not exist in classical supercomputers: quantum states cannot be copied, and physical transportation exposes them to noise and decoherence. Ideally, multiple quantum platforms would share quantum states and operate on those states while avoiding the physical movement of qubits as much as possible. This would allow multiple quantum platforms to be “virtualized” into a single ultra-large platform with effectively a great number of qubits to unlock new computational problems beyond the capabilities of any classical computer.

Nonlocal Gates

One of the keys lies in harnessing the spooky action to build nonlocal gates.

Consider a classical computer. A logic gate occupies a specific location and area on a chip. Through the materials used in the gate, its structural design, and other factors, the gate maintains the intended logical relationship between its input and output signals. For example, if we want to perform an XOR operation on two classical bits, we must transmit the signals carrying those two bits to the input ports of a single XOR circuit, positioned at a particular locality in the circuit system, and capture the result at its output port.

A nonlocal gate, in contrast, can perform a logical operation on multiple input data located in different places, despite the distance between them. Imagine in Laboratory 101 a quantum platform contains a qubit in quantum state , while in the neighboring Laboratory 102 a quantum platform contains a qubit in quantum state . Through a nonlocal gate, without moving either or , we can “snap our fingers” from afar and make the quantum state of become , at the cost of one pre-shared entangled pair and one classical bit sent in each direction.

Let’s study the Remote CNOT described in Eisert et al. 2000.

CNOT, or controlled-NOT, is a 2-qubit gate. It has two inputs, control in and target in, and two outputs, control out and target out. Its rule is simple: when control in is , target in is flipped (more precisely, an gate is applied) to produce target out; otherwise, target out is equal to target in. CNOT is one of the most basic logic gates and is included in the universal gate sets of many computing platforms.

A regular CNOT operates on two qubits that are adjacent in physical space—that is, local. A Remote CNOT goes beyond locality:

• Alice and Bob are separated and each hold one qubit, and .

• In addition, Alice and Bob each hold one qubit of an entangled qubit pair, and .

• Through the Remote CNOT, Alice and Bob can perform CNOT(, ), using as the control and as the target. If is , remains unchanged; if is , is flipped.

Consider the circuit:

The entire procedure consists of 6 steps:

1. Prepare an entangled pair in the Bell state, with the two qubits denoted as and .

2. “Distribute” and to Alice and Bob, respectively. How to “distribute” without physically transporting the qubits will be discussed below.

3. Alice entangles her qubit with .

4. Alice measures , thereby consuming it, and communicates the measurement result to Bob through a classical channel. Bob then uses that information as the control bit to run a CNOT on , a local correction.

5. Bob entangles his qubit with .

6. Bob measures , thereby consuming it, and communicates the measurement result to Alice through a classical channel. Alice then uses that information as the control bit to run a CZ (controlled-Z) operation on , a local correction.

After these steps, the qubits held by Alice and Bob have undergone a joint state transformation equivalent to that of a local CNOT:

The resources consumed by this procedure are:

• 1 ebit of shared entanglement

• 1 cbit of classical communication in each direction

Overall, pre-shared entanglement is a consumable resource. By consuming entanglement, exchanging classical measurement results, and applying local correction operations, we can have two spatially separated qubits jointly execute a logic gate without physically transporting either qubit.

4. Commercial Ambition

Entanglement Swapping

For both the quantum teleportation circuit and the nonlocal gate, steps 1 and 2 are “prepare an entangled qubit pair; distribute the entangled qubits to the two parties.” The question is: how do we distribute the entangled qubits without physically transporting them?

In fact, we do not distribute the qubits. It is not the case that and are prepared somewhere and then distributed to Alice and Bob.

The practical approach is to use photons as “flying qubits” to transform a pair of qubits already held by Alice and Bob into an entangled state.

More specifically, neutral-atom and trapped-ion platforms prepare entanglement resources in the following way:

1. Alice and Bob each allocate one qubit, denoted as and , to be transformed into an entanglement resource.

2. Repeat the following steps until success:

   1. Alice and Bob each excite the qubit in their possession, causing it to emit a photon, denoted as and . The qubit–photon pair is entangled, and the pair is also entangled. The specific method of excitation will be discussed below.

   2. For either party, after successful entanglement, the state of the qubit–photon pair can be described by the following expression: . This means that there is a 1/2 probability of measuring “qubit in 0, photon in horizontal polarization,” and a 1/2 probability of measuring “qubit in 1, photon in vertical polarization.”

   3. Send the two photons and to an interference station. Here, we perform interference with the two photons so that the spatially separated qubits and become entangled. This involves 2 steps:

      1. Send the 2 photons into a beam splitter with 2 inputs and 2 outputs. Our goal is to “mix” them so that the 2 output photons cannot be individually traced back to their corresponding input photons. Functionally, this is analogous to a cryptocurrency mixer. If successful, the 2 photons can be treated as a joint system.

      2. Measure the polarization directions of the 2 photons. This measurement procedure is called a Bell-state measurement (BSM). When the measurement result shows one of the specific combinations of polarization directions, we can declare, or herald, that and have successfully entered an entangled state. If we fail to see the specific combinations in our BSM result, we return to step 2a and repeat until this step succeeds.

This procedure transforms two qubit–photon entanglement pairs, and , into one qubit–qubit entanglement pair . Proposed in 1993, this procedure is called entanglement swapping.

We are still missing a piece of the puzzle: in step 2a, how is the qubit–photon entanglement generated?

Qubit–Photon Interface

How can a qubit be “excited” so that the photon it emits becomes entangled with ?

Consider a neutral-atom or trapped-ion qubit in free space. A laser pulse excites , which then decays and emits a photon . If the excited has multiple decay paths available, the energy level of after emission and the state of , such as its polarization direction, may become entangled.

However, carrying out this process in free space involves at least the following 3 variables:

1. To which energy level will the excited decay, and what frequency will have?

2. In which direction will the excited emit ?

3. How much time will pass between excitation and emission?

For Variable 1, we want to return to either or after emission. Any quantum platform, using neutral atoms or ions of a particular element under a particular external magnetic field, defines its particular as its computational subspace. For classical computing, the “computational subspace” is the pair of voltage levels {0 V, 1.2 V} on a CMOS chip, interpreted as logical 0 and logical 1, respectively. If ends up outside after emission, this constitutes a leakage from the computational subspace. If the leakage cannot be corrected, we lose quantum information.

For Variable 2, radiation in free space may be carried out randomly in many different directions. When the direction is uncontrollable, we have low efficiency in photon collection.

For Variable 3, the emission time in free space is also random. More specifically, the waiting time until decay follows an exponential distribution. A cavity, by contrast, can shorten and shape the photon’s wave packet, making it easier for the photons from Alice and Bob to overlap at the beam splitter and allowing a higher repetition rate.

To make the decay path, emission direction, and timing more controllable, researchers use cavities to alter the electromagnetic environment surrounding the qubits. This is an application of the Purcell effect. In 1946, Edward Purcell, while studying nuclear magnetic resonance, proposed in a brief conference abstract that if an emitter is placed inside a cavity and the cavity’s mode resonates with the emission transition, the rate of emission is enhanced. This cavity-induced modification of the spontaneous-emission rate is known as the Purcell effect.

By constructing the cavity from two opposing mirrors and carefully designing the cavity geometry and qubit placement, we can better control the decay path, direction, and timing of ’s emission. If one mirror is made slightly more transmissive, it can serve as the “egress,” allowing to leave the cavity, enter an optical fiber, and travel to the interference station. Wilk et al. 2007 is one of the early representative works that realized such a design.

The Ambition of Nu Quantum: Datacenter-Scale Distributed Quantum Computing

Nu Quantum is a British company spun out of the Cambridge Cavendish Laboratory in 2018. It aims to become the “Cisco” of quantum datacenters in the future by providing networking solutions that connect quantum computers and realize distributed fault-tolerant quantum computing.

Nu Quantum uses cavities as qubit–photon interfaces (QPIs). The figure below comes from Nu Quantum’s PCT patent application WO2023073379A1; a UK patent in the same family, GB2612578B, was granted in 2024.

A walkthrough of the main components in the design:

• 104a and 104b are the two mirrors that form the cavity.

• 112 is the qubit.

• 106 is the cavity itself, the gap between 104a and 104b; the laser pulse that excites the qubit enters from the side, along the dashed arrow on the right.

• 114 on the left is a mechanical actuator. Using Pound–Drever–Hall frequency stabilization, together with mirrors 102 and 108 (rigid extensions of the cavity mirrors 104a and 104b), the distance between the mirrors is dynamically locked, which maintains the stability of the cavity-mode frequency.

According to a paper published by the team in 2025, the cavity is approximately 370 µm long, with a waist of approximately 5 µm. A 2024 press release further stated that the cavity length could be locked to within 0.08 nm. For the 780 nm transition commonly used with rubidium-87 neutral-atom qubits, this corresponds to a frequency error of approximately % (about 80 MHz).

O’Reilly et al. 2024, from Monroe’s group, represents the state of the art, achieving a successful entanglement generation rate of 250 events per second, or 250 Hz. Because quantum supercomputers will require large amounts of entanglement resources, under continuous replenishment, to perform nonlocal gates, the entanglement generation rate is critical. One of Nu Quantum’s near-term goals is to increase this rate by another 2 orders of magnitude.

Nu Quantum’s broader goal is to virtualize multiple quantum platforms—also known as quantum processing units, or QPUs—under the roof of a single datacenter as one distributed platform. At present, their networking solution supports only trapped-ion and neutral-atom platforms. The solution involves 3 layers:

1. The QPI forms the lowest layer. Installed within each quantum platform, it generates the qubit–photon entanglement described above and outputs photons.

2. The next layer is the Quantum Networking Unit, or QNU. It routes and pairs photons arriving from different QPIs, repeatedly performs Bell-state measurements until successful heralding, and creates shared nonlocal entanglement resources between arbitrary pairs of QPUs.

3. The upper layer is Distributed Quantum Error Correction, or DQEC (refer to their 2025 paper). It performs error detection and correction across multiple QPUs, allowing the physical qubits distributed among them to be abstracted into functional logical qubits to be used by quantum software.

The Ambition of CavilinQ: High-Rate Quantum Interconnects

CavilinQ, founded in 2025, shares the long-term vision of joining many separate quantum computers into one far larger machine through photonic links. CavilinQ is focusing on raising the bar on the rate and fidelity of QPIs so that photons from separate processors can be interfered and the distant qubits entangled with a higher interconnecting bandwidth.

The crux of the QPI is the interface between a qubit and the photon it emits. CavilinQ builds cavity-based interfaces that make this emission fast, directional, and well-timed, making the subsequent heralding step faster and more reliable. The team has integrated more than 5 different types of cavities with quantum memories, a hands-on experience that is rare in the field and central to making interconnects work in practice.

Recall that in a QPI, the cavity’s resonant-mode frequency must be brought as close as possible to the decay transition of the qubit. The closer the two frequencies are, the greater the probability of inducing the qubit to undergo the desired decay. One key metric is the cavity finesse, a dimensionless ratio. Raising the finesse (lowering the losses inside the cavity) and shrinking the beam waist strengthen the coupling between the qubit and the cavity mode, so that more photons go into the cavity mode and then out through the egress mirror.

A recent paper by its team presents a new cavity fabrication process that achieves a finesse of about 0.9 million at a wavelength of 780 nm. A brief description of that fabrication process is as follows:

1. Smooth the surface of a silicon wafer.

2. Use ion-beam sputtering to deposit a coating on one side of the silicon wafer. The coating consists of dozens of alternating layers of high- and low-refractive-index materials, creating high reflectivity within the target frequency range.

3. Flip the silicon wafer over, apply photoresist, and perform silicon etching. The silicon substrate beneath the openings in the photoresist pattern is etched through, exposing the back side of the coating. As a result, the coating becomes suspended, and its internal stress causes it to bend into a concave mirror.

4. Remove the photoresist. The individual mirror chips were already released from the wafer by the through-etch in step 3, so no dicing is needed. Bond two concave mirrors facing each other to form a cavity.

Beyond scaling quantum computing, the team is interested in the following applications:

Blind Quantum Computing

The concept of blind quantum computing (BQC) was proposed as early as 2001 (Childs, Secure assisted quantum computation, published in 2005). Its defining property is blindness: the server learns nothing about the computation it performs on behalf of the client.

Suppose:

• Alice possesses a valuable quantum state , a proprietary quantum algorithm , and only limited quantum computation resources (e.g., some quantum memory and the ability to execute simple Pauli gates).

• Bob is willing to rent out access to his universal quantum computer.

A BQC protocol allows Bob to act as Alice’s delegate. Bob computes and returns the result to Alice, while learning nothing about either or .

The BFK protocol, proposed in 2008 (Universal blind quantum computation, published in 2009), removed any need for quantum memory or quantum gates on the client’s side: the client only prepares random single qubits, yet can have arbitrary quantum algorithms executed blindly. In 2016, Takeuchi et al. (Fault-tolerant verifiable blind quantum computing with logical state remote preparation) extended the BFK framework with stronger theoretical fault tolerance, which allows the server to execute longer gate sequences and tolerate higher levels of noise.

In 2025, Baranes et al. (Designing fault-tolerant blind quantum computation) designed an architecture that scales to fault tolerance while keeping the client’s requirements minimal:

• The client only needs the ability to measure server-sent photonic qubits in arbitrary bases (directions). The client does not need to store quantum states or perform quantum gates.

• The server needs a QPI: matter qubits are repeatedly coupled to photons, which are sent to the client for measurement.

This approach substantially reduces the cost of deploying BQC and broadens its market potential.

Super Long Baseline Interferometry for Astronomy

Quantum interconnects can be applied to astronomy. The basic idea is to exploit the nonlocal nature of quantum entanglement to (1) improve angular resolution by extending the baselines of astronomical interferometers, and (2) increase sensitivity by avoiding the need to physically transmit astronomical photons.

We first briefly introduce a few famous astronomical interferometer systems.

1. Event Horizon Telescope (EHT). Conceptual and experimental work began in the early 2000s. The project was formally launched in 2009 and reached operational maturity by 2017. The EHT uses a technique known as Very Long Baseline Interferometry (VLBI). Telescopes distributed across the globe are first synchronized using atomic clocks. These telescopes then observe the same distant astronomical source simultaneously and record phase information in electrical signals with extremely precise timing. These signals are then brought to a central correlator facility, where timing offsets are corrected and the signals are computationally combined to produce interference fringes, from which an image of the astronomical source can be reconstructed. The EHT produced the first direct image of a black hole. In April 2017, 8 radio observatories around the world observed the target simultaneously, collecting roughly 3.5 PB of data over about 40 hours. After nearly 2 years of data processing and analysis, the black hole image was released in April 2019. The EHT operates at a wavelength of about 1.3 mm (230 GHz), in the millimeter-wave radio band. Moving to still higher observing frequencies is difficult due to factors such as the stringent timing requirements exceeding the capability of atomic clocks, and atmospheric absorption by water vapor. The EHT achieves an angular resolution of about 20 microarcseconds in the radio band. This is equivalent to distinguishing a ping-pong ball on the surface of the Moon from Earth.

2. Navy Precision Optical Interferometer (NPOI). Completed in 1994, the NPOI is a Y-shaped array with three 250-meter arms. Its siderostats can be moved between piers along the arms to vary the baseline length for adjusting the angular resolution. Starlight collected at the stations is then transported in vacuum pipes. Adjustable optical delay lines are deployed along the pipes to compensate for differences in path lengths so that the extremely faint light collected by the stations arrives simultaneously at a central beam-combining facility to execute interference. NPOI’s maximum design baseline is about 437 meters, corresponding to a theoretical angular resolution of about 0.2–0.4 milliarcseconds. Unlike the EHT, which operates at millimeter wavelengths, the NPOI operates at 450–850 nm, covering the visible spectrum. For comparison, the Hubble Space Telescope has a visible-light angular resolution of about 50 milliarcseconds.

3. Center for High Angular Resolution Astronomy (CHARA). With first fringes in 1999 and its dedication in 2000, the CHARA array has a maximum baseline of 331 meters. It operates across visible and near-infrared wavelengths at about 500–2,500 nm, corresponding to angular resolutions of about 0.3–1.5 milliarcseconds, depending on wavelength. Like the NPOI, CHARA transports the faint starlight collected by its telescopes through vacuum pipes to a central beam-combining facility to execute interference. The array consists of 6 telescopes. Pairing the telescopes provides 15 distinct baselines.

Both NPOI and CHARA share a fundamental limitation: to improve angular resolution requires longer baselines, but that means transporting faint starlight over longer distances, which increases loss and phase fluctuations. Measuring the light separately at each station instead, as radio VLBI does with local oscillators, introduces vacuum noise from zero-point fluctuations, which is too much for faint starlight.

Is there a way to interfere the starlight captured at spatially separated observatories without physically transporting the starlight?

Yes, there is: by performing nonlocal interferometry.

The basic idea was proposed around 2011 by Gottesman et al. (Longer-Baseline Telescopes Using Quantum Repeaters). In the same year, Mankei Tsang (Quantum Nonlocality in Weak-Thermal-Light Interferometry) showed that in the weak-light regime, nonlocal approaches that measure the light from both stations jointly achieve strictly higher precision than local approaches that measure each station separately and then combine the results, such as the heterodyne detection used in radio VLBI.

In 2025, Stas et al. (Entanglement assisted non-local optical interferometry in a quantum network) demonstrated nonlocal interferometry using weak laser pulses as stand-ins for starlight. The two stations were about 6 meters apart; spools of optical fiber extended the effective baseline to 1.55 km.

Their experimental procedure:

1. Each of the 2 stations is equipped with a quantum memory with 2 qubits: a memory qubit and a communication qubit. We denote the memory qubits by and , and the communication qubits by and .

2. The 2 stations prepare an entangled pair in the antisymmetric Bell state and store them in their memory qubits , which provide a longer coherence time.

3. An astronomical photon may arrive at any time in a spatial superposition over the 2 stations.

4. When an astronomical photon arrives, with some probability it interacts with the communication qubit at each station, which writes its information into and .

5. Interfere the astronomical photon on a beam splitter with a weak coherent pulse from a local oscillator, whose photon number is itself uncertain. This erases the possibility of telling which station the astronomical photon arrived at, which preserves its spatial superposition.

6. At each station, execute a CNOT gate over its qubits, with the memory qubit acting as the control. Recall that were prepared in an entangled state. If and contain information from the astronomical photon, that information has been transferred into the joint state of .

7. Measure and (specifically their spin direction). In an even outcome (both spin up or both spin down), we know for sure that the astronomical photon was successfully captured by the system. In an odd outcome, the photon was not captured.

8. Conditioned on successful photon capture, the system is now in a state . The sign depends on the spin directions measured for and . We are interested in , the relative phase of the astronomical photon’s spatial superposition between the 2 stations.

9. Measure the above system state.

10. Repeat steps 2–9 many times to statistically estimate the value of .

Given and system parameters such as the baseline length, we can infer the position of the astronomical source and reconstruct its image.

One can imagine a future network of nonlocal interferometric stations distributed across the globe. To achieve even longer baselines and avoid the atmospheric interference from water vapor, we could deploy the system on a network of satellites. Such systems would allow humanity to probe the mysteries of the starry sky in greater depth.

「只要將整個世界倒轉 90 度，人們就會發現一個平時難以啟齒的真理：躺平才是真正的站立，而站立的正是爬行。」——躺平主義宣言

躺平不可恥，且有用

這些年來我的身邊有兩種人，為了迫近自己的理想，不惜一切工夫改造自己的人；以及躺平的人。因為種種原因而躺平的人，你很難看到他們為了特定的事情奮起。他們喪失了行動的慾望，尤其是漢娜．鄂蘭眼中最能彰顯人性的政治行動，因此這樣的群體不太容易被行動者接觸；而行動力越高的人，往往越孤獨，許多時候他們已經不想白費力氣說服躺平的人了，尤其是在工具開發的領域，即使這悖離了他們原先想要讓世界更好的方向。

但是說也奇怪，這兩種人都願意與我交往，可能是因為我曾混跡於政府、大型組織之中，也能夠在合作社、分散式自治組織中生活。我能操持兩種語言。我曾試圖喚醒裝睡躺平的朋友，也曾勸導走太遠的人慢下來。但後來發現這樣根本是緣木求魚，若換一個角度看，或許躺平才是真正的站立，如果能夠躺著逼近理想，這就驗證了一句老話，一個人可以走得快，但一百個人往往能走得遠。

真正有益的科技，其大規模傳播或許來自於懶散的群體。如同 KK（凱文．凱利）所說，人類是科技的生殖器，沒有生殖器（人類）的科技將無法演化，再好的科技沒有繁衍的機會，只是生殖器（人類）的空談；另一方面，群體會產生許多一開始無法預見的綜效，諸如公共衛生領域有群體免疫、國際關係領域有集體安全、而複雜科學有湧現的集體智慧等現象。

因此吾人以為，適合躺平的科技是最適合繁衍的科技，本文將著墨於「躺平蓄銳」的精神狀態，推敲它如何推動我們走向真正需要的科技應用，尤其是最需要身體力行的密碼龐克領域。在密碼龐克的世界中，追求極致的完人，需要採用各種工具、習慣、生活方式來消滅自己的足跡，好好隱藏自己。這樣子的完人實在太辛苦了，社畜實在是沒有閒工夫追隨完人，即使是在最極端的政治環境，風聲鶴唳之中，社畜也僅僅能夠達到蘇聯時期的廚房談話，在茶餘飯後沒有人監控的空間中，稍稍表達自己。即便社畜起了興趣想要走向隱私安全的世界而選擇報名講座，聽完課什麼都忘了。

尤其是完人、先行者、先知太過於耀眼，這實在不知道是好事還是壞事，在救贖之日到來前，先知早已仙逝。還不如藏樹於林的普通人。但現在的社會獎勵拿著錘子的人，這些人可能是創業家、開發者、說書人、網紅、公共知識份子，群眾喜歡看到他們到處錘釘子，這反而暴露了他們的行蹤。他們如同吹笛人一樣，將過街老鼠趕入水中，藏在森林裡的樹就禿了。

這在密碼龐克領域產生了一個悖論，兜售、宣傳好的隱私工具的人，反而是最顯眼的。即便他們手上擁有最厲害的隱形斗篷，也需要暫時脫下來。他們為了達成「宣教」的任務，讓更多人使用隱形斗篷，他們必須暫時解除隱身。

因此本文試著討論，如何做一名懶散的密碼龐克份子，在「完人」與「社畜」之間找到一個兼容並蓄的狀態，在集體躺平的精神文明中，讓保護自己與群體的科技慢慢佈建。密碼龐克仍然可以很酷，但或許可以酷在裡子，外頭罩著一襲灰衣，是為灰衣龐克（GrayPunk）。

穩定且低調的科技擴散，可能是探討生存科技的重要觀念。因此我關心的是如何讓大眾足夠安全，避免追求把菁英鍛造成完人。

當自我審查成為膝跳反射

上一章討論到躺平者與行動者，這恰恰是在集體的壓迫下產生的自然反應，這種反應分裂出了兩個全然不同的方向。先不討論壓迫的原因是否正義、符合時代精神、是否悖離人權。單就個體面臨更巨大的壓迫而言，若借用壓力反應的語言，人會產生生物學最基本的戰、逃與僵住的反應。

行動者接戰，他們無所不用其極，如同在水泥縫隙裡長出的玫瑰花，當然多數行動者失敗了，棒打出頭鳥；而躺平者既不接戰，也無處可逃，其狀態可類比為僵住，就像裝死撲街的羊，人類也是躺下了，躺在社會的結構裡面，在工作、生活、娛樂之中躺平。或許是適應了，或許是放棄抵抗了，他們有效地不對壓迫產生反應，偶有不適，但終歸是可以生存，這樣的精神狀態也常存於某些東方社會。

再讓我們往下討論東方社會中的從眾文化。本文所稱的「東方人」，特指受到儒家文化圈影響的人，我們習慣不在公共場合表達自我，有時候連舉手發言都會倍感壓力。「與他人相同」或許是存活的一大習性，在經年累月的社會化過程中，試著與他人相同已經成為了膝跳反射。讀空氣、不麻煩別人、體味管理等等的概念，都是相似的概念群集。

這樣的從眾文化，甚至還不需要由上而下的壓迫，就會自然產生一種內生的自我審查。我們在發表特立獨行的觀點之前，會先思考過一輪這些糾結，這樣講會不會突兀、會不會讓他人無法理解、會不會造成他人負擔，這就是一種最基礎的自我審查。而審查的尺規，來自於自我想像中的集體意識。雖然名為集體意識，但其實是各自潛藏於心的，所以或許定義為「個體自我以為的集體意識」可能來得更加精準。

但恰恰當每個人都保有這樣的集體想像時，集體性就出來了，而這類集體性只要在大量的行為、試誤、修正中迭代，最終就會導致動態的集體意識於焉誕生，這可能就是從眾行為的原點。這可不是「想像的共同體」所必然帶來的正向結果，我們當然可以說這是某種民族性、文化性的集合，但從壞處來看，當自我意識主動地委身於集體意識之下時，從眾令人感到（但實際上不保證）安全，同時也讓人平庸。

Timur Kuran 的「偏好偽裝」與 Noelle-Neumann 的「沉默螺旋」補足了這個迴路。人們因預期制裁或害怕孤立而隱藏私人信念，公共空間因此高估主流意見的支持度，進一步強化沉默。Jonathon Penney 對維基百科瀏覽行為的研究也顯示，政府監控受到廣泛報導後，部分敏感條目的瀏覽量下降，連合法的閱讀行為都可能出現寒蟬效應（Penney, 2016）。

這讓想要在社會中走跳的人，無時無刻都內建了自我審查的神經迴路。發言前要想一下、舉手前要想一下、行動之前也要想一下。如果這樣的自我審查出現在威權乃至於極權的政治環境，由上而下的壓迫只為了維繫霸權文化，那自我審查與集體審查就真的合為一體了。久而久之，自我審查的人甚至可能出現制度正當化（system justification）的傾向，形成以霸權為榮的慕強文化，即使該個體是受迫於權力，只有義務而沒有權利而不自知，仍然會出現這樣微妙的精神狀態。

如何簡單辨識究竟從眾文化中，有沒有來自上層壓迫的情形，或許我們可以導入政治哲學家佩提特（Pettit）提出的眼球直視測驗。當一個人面對不同對象時，可能是伴侶、同儕、家人、上司、政治人物、執法機關，你會不會避開視線，把頭別過。如果會，很有可能對方在抽象的權力世界中，比你更高一等，這便可能顯示你正處於受支配的關係中。讓我們再換一個問題發問，如果你對著鏡子看自己，想到某些艱難到可能要自我審查的議題時，你會避開自己的視線嗎？

因此在東方社會的從眾文化中，這裡誕生了集體審查與自我審查互相共振而強化的監控氛圍，且有數以億計的人生活於這樣的環形監獄之中，大環之中有小環，大環為無孔不入的監視者，小環為相由心生的自我約束。當審查成為日常，黑話與反話就會應運而生，華文世界可能擁有最強大的黑話文明也說不定。

以互相𤲍燒（取暖）反抗集體監控

我們常常在華文的社群平台上看到引人疑竇的貼文，這些文章常常讓人得想兩圈，才會清楚作者想要表達什麼。或者說作者想要表達給誰，迴避給誰，這正是黑話的藝術。

其一是正話有明確的風險，所以有說黑話的需求，比如關鍵字過濾審查，這是一個高效的數位文字獄。比如當使用者的文章中使用到某些權力者不樂見的關鍵字時，文章被下架、帳號被消滅，或者更令人心驚肉跳的是使用者本人被請喝茶。隨著由上而下的控制以及集體審查的網路文化脈絡逐漸形成，審查字典被慢慢地建立起來。當然使用者會慢慢摸清審查工具的邊界，抓到禁句，接著自然而然地發展出黑話或者反話，讓單純的關鍵字過濾無法起作用。

過去十來年，網路文字審查常見的方式是單純的關鍵字過濾，也就是當關鍵字出現在文章中，文章就會被下架；但是到了最近幾年，大型語言模型的出現，讓上下文脈絡、文字意圖的分析能力飛速發展，再加上既有的文體計量學（stylometry）等工具，讓揪出特定使用者的法寶功力飛升。

其二是黑話可以簡單區辨敵我，看得懂黑話的人同屬於自己的部落，看不懂的皆屬異邦人。黑話、或者反話需要在共同的生活經驗中累積，這不是中心化的標準字典、具有權威的大學老師或新聞編輯可以定義出來的東西，每一個世代、區域、社群都很有可能有自己的黑話，尤其是在風聲鶴唳的公共空間中，黑話存在的意義更重要了。

文字本身具有雙重性，完全一樣的語句，在不同的脈絡下有完全不同的解讀方法，這本身是沒有加密的。簡單的黑話能強化人對陌生人的信任，這是因為能操持黑話的人，至少共享了同一段文化，如同一段卡通、動畫、電影、音樂的台詞，或者影響甚巨的政治事件，或者單純湧現的迷因，這些都可以是黑話誕生的地方，難以預設。

James C. Scott 將權力面前的順從表演稱為「公開文本」，把權力背後保存的批判稱為「隱蔽文本」。黑話正是兩者之間的灰色通道，它讓隱蔽文本進入半公開空間，同時保留否認與退卻的餘地（Scott, 1990）。King、Pan 與 Roberts 對中國網路審查的研究則指出，審查特別針對具有集體行動潛力的內容；黑話所保存的因此不只有表達空間，也有辨識同伴與協調行動的能力（King, Pan & Roberts, 2013）。

由於具有雙關意義的黑話沒有加密，任何人努力一點，嘗試偽裝成自己人是非常容易的，只要學會幾句黑話，就可以簡單地融入社群，這是黑話的風險。但這也是為什麼黑話與反話發展的速度非常快，快到大眾還沒有理解一個人究竟是支持還是反對某個立場，他到底是在說反話，還是真心這麼認為，一個演化中的部落符碼可能就繼續往下遞移了。此時不免許多人會這麼想：「既然這麼混亂，乾脆放棄辨認好了」，因此躺平的人越來越多，這便可能形成理性無知（rational ignorance），從而導致導向資訊退避與政治疏離（political disengagement）。

但這並非舒適的躺平，躺平不會這麼累。因為這段躺平的心路歷程中，充斥著自我審查，在這樣充滿數位文字獄的社會中，公民需要有意識地迴避特定地方才能免於災難，因此在心智地圖中，自然地產生了一塊塊不可踏入的禁區，這是充滿自我審查的躺平。如果想要真正舒適的躺平，便需要解開心結，攤平心智地圖，有意識地解開膝跳反射的神經迴路。

在此有兩項解方，一個是個體的，一個是集體的。個體方面需要在不放棄思考的前提下建立數位衛生習慣，為此不需要做過頭，只要發揮我們無時無刻從眾的文化氛圍，不要落後群體太多，也不要超出群體太多，此外當然需要建立正確的資訊安全、隱私安全觀點，並依照實際的風險（威脅模型）判斷真正需要做到多遠，我把這樣的生活方式，稱為灰衣龐克。集體的解方則是把足夠安全的做法變成群體預設，避免每個人都必須獨自維持高警戒，後文將由此展開。

灰衣龐克衍生自密碼龐克，而密碼龐克（Cypherpunk）一詞借名於賽博龐克（Cyberpunk）。賽博龐克作品往往對科技能力的成長抱持想像，卻對文明與權力關係保持悲觀；它所描繪的未來，是人機合成的、階級問題仍然存在、榨取式經濟繼續掠奪眾人與環境，科技服務人類，但只有頂端人口是人類。

而密碼龐克借用了賽博龐克的命名，並試圖用密碼學回應其描繪的惡托邦，支持密碼龐克的人更加安那其，說白了他們不大相信政府、企業或者國際組織可以保障個體的安全，安全應該要從自己的實踐做起，包含隱私安全的工具，以及自成一格的交換體系，如貨幣、文化、語言、網路基礎設施等等。

密碼龐克者是一群很特殊的次文化團體，主要由密碼學家、具有政治行動意志的駭客、學術團體等組成。他們雖然人數稀少，但是在數位文明的歷史上已經是不可或缺的角色，因為他們在與國家的官司攻防、開源技術發展上已經打了許多場勝仗，中西皆然。不過密碼龐克者之中也有多元價值觀，如典型的自由意志主義者，或者更加左派的團結精神，所在多有。

灰衣龐克作為一種新龐克

但是本文所提出的灰衣龐克並不需要這麼慷慨激昂，或者聰明肯幹才能加入。我們不妨試著將密碼龐克從此類講究世界終將進步的輝格式史觀剝離，再佐以「躺平」發懶的精神，或許這樣的科技發展取徑才是真正推動文明進步的方法也說不定。

灰衣人（Gray Man）是在行動安全（OPSEC）與生存準備社群常見的用詞，指的是讓自己在人群中看起來普通、沒有辨識度、不值得被特別注意，這是一種常見的、低成本的避險、反監控策略。例如一個人如果全副武裝，穿著全副高檔戰術裝備，並且帶著特殊器材，雖然他可能會覺得自己很安全，但實際上反而會提高可辨識性。灰衣人的思路反而是融入環境中，降低可見度（low profile），使觀察者難以記住你，也缺乏理由持續注意你。

灰衣龐克的核心精神不是發展超出世界科技樹的隱形斗篷，而是「不突出」於人群。這樣的概念非常適合花了一輩子養成從眾精神的東方社會，因為要融入人群，就必須識別人群，我們練就的自我審查伎倆，完全可以派上用場，只要換個方向即可。我們知道如何穿著大家都會穿的衣服，在對的時間點出門、舉手發問，我們知道如何不與他人起衝突，達成目的。

但我們仍然知道自己很酷，這樣的酷決計不是外在的，不需要理龐克頭、刺青、穿鼻環等等，酷是酷在內裡的姿態，我們有自己的龐克精神，潛藏在一襲灰衣底下，而這樣的酷找得到夥伴，且必須有夥伴。且因為難度比密碼龐克低太多了，因此更容易擁有更大的基數，且更容易從小眾、難以落實的次文化圈層中，慢慢擴散。

此外，數量級的提升，反而實踐了真正的密碼龐克精神。這是因為匿名者喜愛作伴（anonymity loves company）。若要落實真正的躺平，除了個體的安全與日常習慣外，集體安全就是第二個重要課題。一個個體很難強求其他人配合，以達到集體安全；但如果整個社會集體，或部落集體，同時落實了一套沒那麼困難的處事方針，那這套方針就會因為路徑依賴，而長長久久存在於這個群體之中。

如果一個社會講求內卷，互相踩踏，仍然具備前往安全躺平的可能。這是因為個體只要有意識地比別人安全一點點，我們都穿著灰衣，但是當天敵來抓捕灰衣人時，我們又多了一點點防護方法，就更可能倖免於難，擁有這樣思維的人就會行動，久而久之，整個灰衣人社群就會慢慢地升級安全防護的方法，而不是沙丁魚群包成球，等待旗魚來獵食。我們需要將二階思維考慮進科技發展與數位素養發展的過程中，集體安全是動態的，最佳的結果就是整體漸漸向上升級。不過，這個賽局的長期解不能只是把風險轉嫁給更脆弱的人，而要讓整體安全基準逐步提升。

VPN 的發展史恰好可以說明這種道高一尺、魔高一丈的集體演化。VPN 本來可以說是相當無聊的企業資安技術，VPN 讓不在公司的使用者透過加密通道，安全地連進公司內部網路。到了 2000 年代，OpenVPN 等開源工具逐漸普及，自己架設加密通道變得越來越容易。同時中國的網路防火長城（Great Firewall）開始透過 DNS 污染、IP 封鎖、關鍵字過濾等方式切割網路時，這些原先沒有什麼革命色彩的工具，很自然地被拿來突破封鎖。此刻的 VPN 很有可能只是被網路使用者順手使用而已，並不是一個宏大的政治行動。

但防火長城也會學習。當越來越多人使用相同的 VPN 工具，流量本身就成為可以辨識的特徵，於是抗審查技術也跟著改變。Shadowsocks、V2Ray，以及 Tor 的各種混淆傳輸技術陸續發展出來，技術問題開始從單純的加密，轉向混淆流量。研究防火長城的團隊發現，中國的審查系統至少自 2019 年起已經會先利用封包長度、熵值等特徵猜測一段流量是否屬於 Shadowsocks，再派出主動探測器連線到可疑伺服器確認。到了 2021 年，防火長城甚至開始大規模辨識「完全加密」的流量，Shadowsocks、VMess、Obfs4 都受到影響。這時候使用先進技術的人就像是全副武裝的戰士，如果流量的外觀脫離正常協定的模樣，就很容易被視為異常值。

因此混淆技術的發展，轉向了灰衣人模式。當封鎖者愈擅長尋找異常值，抗審查工具就愈有誘因模仿正常值，雙方在一輪又一輪的辨識、封鎖、偽裝與再辨識之中共同演化。這場攻防也已從協定擴張到法規、App 商店與商業服務，但核心仍然相同：封鎖者尋找異常，使用者設法重新融入正常流量。Finn Brunton 與 Helen Nissenbaum 將這類做法稱為混淆（obfuscation），意即有意加入雜訊、歧義或仿真訊號，使資料更難被分類與利用（Brunton & Nissenbaum, 2015）。

這也是灰衣龐克真正容易落實的地方。宏大的網路自由理想，最後的景色絕非人人都成為密碼學家，它可能只是數以百萬計的人養成極其平凡的習慣。當審查升級一點，工具就跟著升級一點；工具變得太難用，市場便有人想辦法把它重新包裝得簡單一點。每個個體都只比昨天多會一點，其實就很龐克了。

因此，灰衣龐克就是集體安全，集體安全就是藏樹於林。在漫長的歷史長河中，我們假定世界上並沒有人類的天敵會一次性地滅絕人類，只有人類之間會互相競爭，因此雖然不保證每棵樹都不會倒下，但整片樹林難以被一次清除。

因此當我們討論集體安全，務必將不抵抗的藝術以及共存的勇氣考慮進來，畢竟這就是生活的現狀。從眾、自我審查、舒服的生活、比別人安全一點點、但同時也有一點酷酷的，這樣的精神早已長存於我們心中。在東方社會，密碼龐克未必是單純的意識形態理想，而是生存必要條件。

密碼龐克為何無法成為主流，以及如何轉向？

縱觀網路發展史，密碼龐克明明打過許多場漂亮的勝仗，如隱私通訊（E2EE）、匿名網路（Tor）、數位簽章（PGP以降）、電子貨幣（Bitcoin、Ethereum、Monero、Zcash）等觀念，也早已深入數位文明，為何密碼龐克始終停留在人數不多、進入門檻很高的次文化圈層？

更精確地說，難以進入主流的是密碼龐克作為一種自覺的政治身分與生活方式。密碼龐克所創造的技術，反而時常以另一種面貌進入主流。當一項工具真正普及，人們不再需要理解其歷史、意識形態與技術細節，它便會脫下龐克的皮衣，變成預設值（by default）。使用者每天受其保護，卻未必知道保護從何而來。這也許正是密碼龐克最成功，同時最不容易被看見的地方。

密碼龐克究竟是什麼？Eric Hughes 在 1993 年發表的〈密碼龐克宣言〉中，將隱私理解為個人選擇向世界揭露多少自己的能力。個人無法期待政府、企業與其他龐大組織出於善意授予隱私，因此必須共同建造能夠實踐匿名交易與私人通訊的系統。密碼龐克最廣為人知的精神，便是「密碼龐克寫程式」——政治立場需要落實成科技工具，不然就只是空談。

這使密碼龐克具有一種「前構政治」的性格。它不只向現存制度提出要求，也試著預先把理想秩序的一小部分寫進協定，這樣的制度設計，其實是一種很左派的想像，因為在程式碼面前，人人平等。這種做法以實作取代等待授權，帶有平等主義的想像；但程式碼提供的形式平等，仍可能被資源、能力與基礎設施的不平等抵銷，因此將程式碼作為社會運動的行動者，進入了一個動態循環之中。當請願要求權力者不要監控人民，密碼龐克試著讓監控在技術上變得更困難；當法律要求政府尊重言論自由，密碼龐克試著建立不容易被單一政府關閉的通訊系統；當人們要求平台善待使用者，密碼龐克試著保留資料匯出、另起爐灶與退出平台的能力。

但早期密碼龐克有時也帶著強烈的科技必然論。只要密碼學持續發展、程式碼散布到全世界，權力似乎終將被技術馴服。這很容易再次滑入本文前面所批判的輝格式史觀。彷彿科技樹具有唯一方向，所有分支最終都會通往自由。

現實顯然更加麻煩。相同的密碼學可以保障異議者，也可以保護勒索軟體；相同的分散式網路可以支撐公共協作，也可以再次讓少數節點、交易所與服務供應商壟斷。技術不會單獨替我們選擇文明的方向。

因此科技顯然不會停止加速，但我們可以選擇要加速的方向。Vitalik Buterin 所提出的去中心加速主義（d/acc），可以視為密碼龐克精神的一次更新。d/acc 的完整意思是「去中心化且民主的差異化防禦加速」，其中的 d 同時指向 decentralization、democracy、differential 與 defensive。它承認科技發展帶來龐大效益，也承認科技停滯可能造成真實傷害，但科技加速不應被理解為不由分說地踩下油門。不同技術會改變攻擊者與防禦者之間的力量平衡，因此必須優先發展讓攻擊更困難、讓復原更容易、讓權力更分散的技術。

這裡的防禦不等同於消極等待，也不等同於把所有權力交給自稱能夠保護大眾的先知。d/acc 所追求的是分散式防禦，讓個人、社群與地方組織各自具備一定程度的保護能力，系統遭到攻擊時不會因為單一節點倒下而全面崩潰，普通人也不必為了獲得安全而永久讓渡自己的資料、身分與行動權。畢竟言而無信的君主，可說是最大的安全破口。

這種思維把密碼龐克從個人隱私往集體安全，乃至於文明防禦推進了一步。加密通訊保護兩個人之間的對話，資訊防禦保護一整個社會的判斷力；多重簽章保護一個人的一筆資產，制度性的制衡與韌性機制則保護一個組織免於單點故障。保護的對象逐漸從獨善其身的駭客（龐克），擴展到社群、組織、公共衛生、資訊環境與民主制度。

從這個角度來看，防禦性技術真正重要的功能，未必是讓最厲害的人變得刀槍不入。它更重要的功能是降低普通人的脆弱性，使人們遭逢一次又一次的變故後，仍然保有重新站起來的機會。這與本文所說的躺平蓄銳恰好相通：因為安全的姿態不在於一直站著警戒，而在於讓人可以放心躺平。

2026 年，以太坊基金會在其使命綱領（Mandate）中將自身必須維護的核心原則整理為 CROPS，分別是抗審查（Censorship Resistance）、開放原始碼（Open Source）、隱私（Privacy）與安全（Security）。綱領將這些原則的優先順序置於便利性之上，不可妥協。綱領同時進一步提出，自我主權（Self-sovereignty）的使用方式必須能夠抵抗榨取，同時具備順暢的使用體驗。

「順暢」尤其重要，密碼龐克社群長期容易把難用視為自由必須支付的代價，但只有專家才能安全操作的自我主權工具，只提供了形式上的選擇。普通人最後仍會將金鑰、資料與判斷重新交給中介者，因為日常生活沒有足夠時間容納一套全職的資安苦行。設計者不能要求使用者為了守護原則而永遠忍耐糟糕的介面。相反地，設計者必須努力把抗審查、開源、隱私與安全做得足夠平凡，使普通人不必每天重新宣誓，也能持續受到保護。這樣普通人才有辦法加入灰衣人的行列。

我曾經提出「戍衛轉型指南」的概念，試圖提供一套日常中可以邁向自我主權與集體團結的方法。今天我們談論數位轉型時，社會彷彿有嗜新症，社會喜歡獎勵發明新東西的人。人們喜歡新平台、新協定、新人工智慧、新治理模式與新創公司，喜歡看創辦人拿著錘子四處尋找釘子。至於維護？那是無人在意的後話。但如同 d/acc 所表達的，科技發展的軸線其實可以由人群集體導引（steering），所以我試著在集體團結與個人自我主權之間，尋找以密碼龐克為基底的相關科技發展與潛藏的次世代技術。

在搜集與分類這些科技的過程中，我發現密碼龐克仍然不是主流，理由有許多，我們一一分析。

i. 不激進就不酷

次文化需要小眾，但安全需要集體，龐克之所以酷，很大一部分來自它與主流社會的距離。當一件事情人人都會做，它便很難繼續充當身分標誌。這使密碼龐克面臨內在矛盾，它希望更多人使用隱私工具，但工具一旦普及，原先藉由工具獲得的特殊身分便會貶值。

在次文化裡，艱深知識、罕見工具、特殊語言與高昂實踐成本，都可能成為一種亞文化資本。以密碼龐克來說，自己架設伺服器、驗證軟體簽章、懂得編譯程式碼、熟悉匿名網路協定的人，當然值得敬佩。但當這些技能同時被拿來證明誰比較酷，此刻技術能力便轉化為社群階級。

黑話在這裡也會產生雙面效果。在受壓迫的環境中，黑話能夠協助同伴互相辨認，避開粗糙的文字審查；進入技術社群後，黑話又可能變成守門機制。菜鳥如果不知道助記詞、熵值、金鑰或混淆的意思，便很難參與對話。這對資訊安全尤其危險。安全需要人們願意承認自己不懂，也願意承認自己曾經受騙。原本用來辨認同伴的身分邊界，也可能妨礙真正的互助。

密碼龐克社群還容易出現正統之爭，也就是誰才是真正的苦行僧。使用某個作業系統不夠安全、把資料放在某個雲端不夠獨立、沒有自行託管節點不夠去中心化、繼續使用主流社群平台不夠反抗。每一項批判單獨來看都看似有理，但加起來後，合格的密碼龐克就只剩下少數能夠投入大量時間、金錢與專業知識的傢伙。

當一項工具要求使用者先完成身分改造、接受一整套世界觀，才有資格獲得基本保護，它很難進入社畜的日常。這使密碼龐克產生一個弔詭的激勵，社群最容易獎勵走在最前面的人，卻不一定獎勵把既有技術做得更無聊、更穩定、更容易使用的人。發明一套新協定很酷，替舊協定補文件沒有那麼酷；提出最極端的威脅模型很酷，替一般人找出足夠安全的設定沒有那麼酷；宣告主流平台全部不可用很酷，設計一條讓使用者逐步遷移的路徑沒有那麼酷。但科技擴散往往依靠後面這些不太酷的工作。

ii. 安全疲勞

密碼龐克無法進入主流的第二個原因，是安全疲勞。如上段所說，一般人沒辦法成為完人。一名完美的密碼龐克需要使用密碼管理器、硬體安全金鑰、加密硬碟、匿名網路、獨立電子郵件、不同用途的身分、端對端加密通訊、離線備份與自行託管的服務。他要定期更新軟體、檢查權限、驗證下載檔案、輪替金鑰、演練復原流程，還要時刻留意照片中是否出現位置、文件中是否殘留詮釋資料、瀏覽器是否形成獨特指紋。

NIST 將安全疲勞描述為人們面對電腦安全時產生的厭倦與抗拒。當警告、密碼規則與安全決定過於頻繁，人們容易感到無力，進而忽略警告，採取風險更高的行為。這個問題的關鍵不在於使用者毫無知識，許多人只是長期遭到超出認知負荷的安全要求轟炸。

因此，低摩擦安全的設計重點不只在教育使用者，也在減少需要使用者記住、判斷與反覆執行的安全決定。Tactical Tech 的 Holistic Security 把數位、實體、組織與心理社會安全放在同一套框架中。一套耗盡行動者的安全制度，終究無法持續。

iii. 沒錢沒辦法躺平

密碼龐克無法成為主流的第三個原因，是維護科技需要資源。開放原始碼可以免費散布，持續維護仍然需要支付成本，許多對世界至關重要的開源專案，令人意外地由一兩位志願者維護，現在世界終於也到了這些網路世界的志願者因為健康因素凋零的時代。一旦維護者耗竭、生病或退出，整個生態系就可能暴露於風險。Steven Jackson 所說的「破損世界思維」（broken world thinking）警告我們，技術秩序主要靠修補、照料與維護而延續；這些工作不如發明新協定顯眼，卻決定系統能否活下去（Jackson, 2014）。

隱私工具又面臨特殊的商業困境。許多免費消費科技透過蒐集使用者資料、投放廣告與預測行為獲利，但保護隱私的服務若採取相同模式，便會與自身使命衝突。Signal 曾公開說明，維持一套全球性的私人通訊服務需要龐大的基礎設施與開發支出，而監控型商業模式長期使使用者誤以為消費科技理所當然應該免費。商業化本身沒有天然的背叛性。真正的問題是收入來源與使用者安全是否一致。訂閱制、合作社、公共採購、基金會捐助、付費技術支援、交叉補貼與公共財資助都可能成為解方。

而把安全做成預設值，本身也需要穩定的資金、維護與文件工作。

歷史上真正進入主流的安全科技，往往都曾完成一次「去儀式化」。

HTTPS 的普及沒有依靠全世界的網站管理者共同成為密碼學家。Let’s Encrypt 以免費、自動化與開放的憑證服務降低部署成本，ACME 協定又讓憑證申請與更新可以大量自動完成。Let’s Encrypt 在 2020 年發出累計第十億張憑證，並直接將易用性與自動化視為擴散的重要基礎。端對端加密通訊進入大眾生活，也沒有依靠數十億人先理解金鑰交換。WhatsApp 在 2016 年將端對端加密設為通話與訊息的預設狀態，使用者不需要另外啟動加密，甚至不需要知道加密正在發生。

這些案例共同說明，科技進入主流很少是因為所有人都接受了一套完整的政治哲學。它進入主流，是因為費用下降了、操作消失了、設定成為預設。密碼龐克技術最成功的時刻，往往也是它最不像密碼龐克的時刻。每天的連線、對話與裝置已經受到那些思想保護。革命被建制派吸收，這或許才是科技真正的繁衍。

iv. 蚍蜉撼不了樹

密碼龐克無法成為主流的第四個原因，是力量高度不對稱。一名開發者可以發明新的抗審查協定，國家卻同時掌握更多權力。前面所述的 VPN 發展史已經顯示，這是一場沒有終局的共同演化。如果密碼龐克想像的是一次漂亮的技術反殺，現實通常會令人失望。國家與大型平台可以輸掉一回合，百足之蟲卻死而不僵，短時間內不會自行解體。

但螞蟻未必需要正面推倒一棵樹，森林也不靠任何一棵樹單獨存活。樹林的韌性來自不同物種之間的共生關係。地面上的一部分遭到砍伐，地下的根系仍可能保存重新生長的能力。因此抗審查技術真正的目標，未必是一次摧毀審查者。它可以是持續提高全面控制的成本、保留替代管道、延緩權力鎖定、讓知識與關係不會隨著單一工具消失。

單一工具容易被瞄準，生態系則可以轉向、變形與再生。這也正是灰衣龐克必須強調集體安全的原因。每個人不需要具備足以擊敗國家的能力，但整個群體需要避免把所有希望押在一個先知、完人身上。

以上四個原因其實互相連動。次文化邊界阻礙擴散，過高的操作成本阻礙實踐，缺乏資源阻礙維護，力量不對稱則使任何單次勝利難以成為永久結果。因此，解方必須同時降低身分成本、操作成本、維運成本與對抗成本。密碼龐克需要從英雄敘事逐漸轉化為日常生活，從少數完人的極致安全，轉化為多數普通人可以長期維持的相稱安全。

灰衣龐克作為一種時尚

時尚最有意思的地方是人們往往先模仿，之後才理解。大多數人不會先讀完一整套服裝史、布料學與身分政治，再決定今天穿什麼。他們觀察身邊的人，看見某種做法似乎方便好看，便跟著採用。時尚因此是一種低成本的群體協調機制，它不要求每位參與者都共享完整的理論，只要求一項做法具有足夠低的模仿門檻。

這恰好可以重新利用東方社會的從眾神經。

從眾原先讓人學會讀空氣、自我審查與避免突出，灰衣龐克試圖把相同能力轉向集體安全。當身邊的人都使用密碼管理器、開啟裝置密碼、定期更新、使用加密通訊、降低不必要的權限，個體不必感到自己正在參加一場革命。他只是做了大家都在做的事。

灰衣龐克沒有統一制服。若需要特定符碼，那套美學已經失去灰衣的功能。灰衣龐克可以有共同姿態，卻不應把姿態固定成容易辨認的東西。灰衣龐克是流動的。它的流行方式接近習慣，而非裝扮。灰衣龐克因而是一種沒有次文化制服的次文化。它保留龐克對權力的不信任、對自主的堅持與對替代系統的想像。它的酷藏在第一眼看不見的地方。

此外懶散也是一種時尚。此處所說的懶散，與疏忽相距甚遠。疏忽是知道風險後仍把問題留給未來的自己；懶散的設計則要求系統預先處理重複、瑣碎且容易出錯的工作。因此，灰衣龐克會把懶散視為一項正式的工程規格。重要的選擇應該出現在真正具有意義的時刻，其餘工作由工具、組織規範與基礎設施承擔。安全若只能在精神飽滿、時間充裕、政治熱情高漲時成立，那就不是適合人類社會的安全。

酷在第一眼看不見的地方。

灰衣龐克的酷，可以用一個反直覺的方式衡量。一項安全技術越少要求使用者注意自己，同時越能保存使用者的自主，它就越接近灰衣龐克。最好的防護往往像建築物裡的消防管線，平常沒有人拍照打卡，火災發生時卻決定誰能活著離開火場。

然而，灰衣龐克仍然面臨一項最重要的倫理問題：如果降低可辨識性，是否會重新導向自我抹除？這會不會瓦解次文化團體進行倡議的能動性？這個問題在東方社會尤其尖銳。如果只是把沉默、服從與失去稜角重新包裝成灰衣策略，那已經是權力獲勝的證明。自我審查不會因為換上一個龐克名稱，就自動獲得解放。

灰衣與自我抹除的差異，可以透過三項測驗加以辨認：選擇權、可逆性與互惠性。

第一是選擇權。究竟由誰決定一個人應該保持低調？如果答案是上司、政府、家庭、社群輿論與內化的恐懼，那比較接近被迫的自我審查。如果個體仍然可以決定向誰揭露、何時揭露、揭露多少，低可見度就成為隱私的一部分。這也回到 Eric Hughes 對隱私的理解：隱私的核心是保有「選擇」揭露自己。

第二是可逆性。灰衣應該是一件可以穿上，也可以脫下的外套。個體在高風險環境中保持低調，仍應在可信任的空間保存自己的名字、記憶、觀點、關係與行動能力。他可以在廚房裡說真話，可以在同伴之間辨認彼此，可以在條件成熟時留下證詞，也可以在必要時重新走進公共空間。一套永遠無法退出的隱身策略，比環形監獄更淒慘。

第三是互惠性。灰衣究竟讓整座森林更加茂密，還是只讓自己躲到別人身後？如果個體把風險轉移給更顯眼、更貧窮或更缺乏技術能力的人，這仍是一種競爭性的避險。灰衣龐克則要求個人的防護能夠創造公共外溢，使其他人也更容易獲得安全。真正的匿名集合不能只靠自己，真正的藏樹於林也不能一面藏身，一面把周圍的樹全部砍掉。

這也呼應前文提到的眼球直視測驗。灰衣不要求人們永遠低頭，它要求人們保存選擇何時抬頭的能力。真正的安全並非讓一個人再也不敢直視權力，而是當他決定直視時，身後仍然有一個不會因為他暫時倒下便立刻消失的群體。用 Albert Hirschman 的語言來說，灰衣可以是一種有限退出，暫時降低暴露，卻保存未來重新發聲的能力。

灰衣龐克也不要求所有躺平者突然站起。躺平者可以用低強度的方式參與。一個人未必願意公開成為政治運動者，但他可以更安全地生活，也可以備份資料、維護文件、資助基礎設施，並教會身邊的人使用成熟工具。這些低可見度的維護工作，本身就是集體安全的一部分。

結語：如何做一名懶散的密碼龐克份子

寫到最後，做一名懶散的密碼龐克份子，其實不需要幻想自己是最後一名抵抗軍，也不需要為了等待世界末日而存錢購買地堡。

我們應該藉由躺平來躺贏。

所謂躺贏，是把對抗拉長成一場耐力賽，對手必須持續投入資源監控、辨識、封鎖與追捕，我們則把安全融入尋常生活，讓每一次迴避的成本低一點，復原的速度快一點。當控制者維穩成本提高，被控制者只需保存不被完全控制的餘裕，躺平便可能形成一種不對稱的優勢。

戰士不需要穿著全副武裝去買早餐。安全也應講究比例，這可以稱為相稱安全（proportionate security）。把所有能找到的防護工具套在身上，未必會讓人更安全，還可能向外露餡，暴露自己的特殊性，同時造成心理疲勞。

懶散的密碼龐克也需要一點安全禪。安全禪講究吸收新知，實踐已經成熟的工具，定期檢視自己的生活，卻不因每一則資安新聞陷入恐慌。不要把焦慮誤認成勤奮，也不要把複雜誤認成安全。真正深厚的安全修行，經常表現為幾個平凡到令人失望的動作。

這也是一場「比別人安全一點點」的賽局。在短期裡，多一點防護可以降低自己成為最容易攻擊對象的機率；拉長時間來看，最穩定的策略仍是讓更多人一起提高安全基準線。匿名者喜愛作伴，使用某項隱私工具的人越少，使用行為本身越可能成為指紋；當使用者足夠多，它才會融入尋常背景。這裡可以借用 k-匿名性（k-anonymity）的隱喻：當一個人與足夠多的他人共享可見特徵，就較不容易被單獨辨認。只有一名灰衣人是沒辦法形成灰衣龐克群體的。

所以我們要做的，不是把自己鍛鍊成永不疲倦的完人。灰衣龐克避開壯烈殉道，也拒絕麻木投降。他選擇一套能在忙碌、疲倦、失戀、失業、生病與政治低潮中繼續維持的生活方式。真正可靠的安全習慣，必須在一個人最沒有力氣的日子裡仍然有效；真正可靠的集體，也必須在一兩個人倒下後仍能繼續運作。

社會運動研究者 Verta Taylor 將運動在退潮期保存組織、關係網絡與集體認同的狀態稱為 abeyance，或許可譯為「潛伏維繫」（Taylor, 1989）。「躺平蓄銳」可以視為這項概念在數位生存中的版本，又或者更進一步，描述一個不滅的慵懶行動者的精神狀態。

躺平蓄銳為王，因為可持續的生活才有漫長的抵抗。舒服地躺下，保持系統運作，與同伴待在同一片森林裡，才是一名懶散的密碼龐克份子最永續的姿態。

本文為 Parity 論文獎助計畫「遙望集」的第一篇。文字 © 2026 黃豆泥，以 CC BY-SA 4.0 授權。

“Turn the whole world ninety degrees and people will discover a truth that is usually hard to say out loud: lying flat is the true way of standing, and those who stand are the ones crawling.” — the Lying Flat Manifesto

Lying Flat Is Nothing to Be Ashamed Of, and It Works

In recent years there have been two kinds of people around me: those who will remake themselves by any means necessary in order to close in on their ideals, and those who lie flat. People who lie flat, for whatever assortment of reasons, are seldom seen rousing themselves for any particular cause. They have lost the desire to act, above all the desire for political action, which in Hannah Arendt’s eyes is what most fully reveals what it is to be human, and so this group is not easy for those who act to reach. Meanwhile, the more capable of action a person is, the lonelier they tend to be. Much of the time they have already given up wasting their breath on people who lie flat, especially in the field of tool development, even though this runs against the very direction they set out in, which was to make the world better.

Oddly enough, though, both kinds of people are willing to keep company with me. Perhaps it is because I have knocked around inside governments and large organizations and can also live inside cooperatives and decentralized autonomous organizations. I can speak both languages. I have tried to wake friends who were lying flat with their eyes shut on purpose, and I have tried to persuade people who had gone too far out to slow down. Later I realized that this was, in Mencius’s phrase, climbing a tree to catch fish. Seen from another angle, lying flat may be the true way of standing; and if it is possible to close in on your ideals while lying down, that would bear out an old saying: one person can walk fast, but a hundred people can usually walk far.

Genuinely beneficial technology may owe its mass diffusion to the lazy many. As Kevin Kelly put it, echoing McLuhan, humans are the sex organs of technology. A technology without sex organs, without humans, cannot evolve, and however good a technology is, if it never gets the chance to reproduce it remains idle talk among the sex organs, which is to say among us. Groups, on the other hand, generate all sorts of synergies that no one could foresee at the outset: herd immunity in public health, collective security in international relations, emergent collective intelligence in complexity science.

I therefore hold that the technology best suited to lying flat is the technology best suited to reproducing. This essay dwells on the state of mind of lying flat while keeping your edge, and works out how it might push us toward the technological applications we actually need, above all in the cypherpunk domain, which of all fields most demands that you practice what you preach with your own body. In the cypherpunk world, the paragon in pursuit of perfection, the “complete person” that Confucian moral education holds up and almost no one becomes, must take up every sort of tool, habit and way of living in order to erase their own footprints and hide themselves properly. Being that kind of paragon is far too much work. Wage cattle (shachiku, as East Asian office workers have learned to call themselves: livestock kept by the company) really have no spare time for following paragons. Even in the most extreme political environments, with everyone jumping at shadows, the most that wage cattle can manage is Soviet-era kitchen talk: expressing themselves a little, after dinner, in the one space nobody is watching. And even when wage cattle get curious enough about the world of privacy and security to sign up for a talk, they forget everything the moment the talk ends.

The paragon, the forerunner and the prophet shine too brightly, and it is genuinely unclear whether that is a good thing or a bad one; long before the day of deliverance arrives, the prophet has already ascended. Better to be an ordinary person, a tree hidden in the forest. But today’s society rewards the people holding hammers, the entrepreneurs, developers, storytellers, influencers and public intellectuals, and the crowd loves watching them hammer nails everywhere, which is exactly what gives away their position. Like the Pied Piper, they pipe the rats everyone wants to beat out into the river, and the forest that hid the trees is stripped bare.

This produces a paradox in the cypherpunk world: the people hawking and evangelizing good privacy tools are the most conspicuous people in it. Even if they hold the finest invisibility cloak going, they have to take it off for a while. To carry out their “missionary” work and get more people wearing invisibility cloaks, they must temporarily switch off their own invisibility.

So this essay tries to work out how to be a lazy cypherpunk: how to find, somewhere between the paragon and the wage cattle, a state with room for both, and how, inside the “spiritual civilization” of collective lying flat (to borrow a phrase the Chinese state is fond of), to let the technologies that protect ourselves and our groups be built out slowly. Cypherpunk can still be cool, but perhaps the coolness can live in the lining rather than on the face, with a gray coat worn over the top. This we call GrayPunk.

Steady, low-key technological diffusion may be an important idea for anyone thinking about survival technology. What I care about, therefore, is how to make the general public secure enough, rather than how to forge an elite into paragons.

When Self-Censorship Becomes a Knee-Jerk Reflex

The previous section discussed those who lie flat and those who act. Both are natural responses of an individual under pressure from the collective, one response that splits into two entirely different directions. Set aside for the moment whether the reasons for that pressure are just, whether they accord with the spirit of the age, whether they violate human rights. Consider only the individual confronted by a force much larger than themselves, and borrow the language of the stress response: people produce the most basic biological reactions of fight, flight and freeze.

Those who act, fight. They stop at nothing, like a rose growing out of a crack in the concrete. Most of them fail, of course; the bird that sticks its head up gets hit. Those who lie flat neither fight nor have anywhere to run, and their condition is best compared to freezing, like a sheep playing dead, flopped in the road. Humans lie down too, inside the structures of society, lying flat through work, life and entertainment. Perhaps they have adapted; perhaps they have given up resisting. They have, in effect, stopped responding to the pressure at all. There is occasional discomfort, but on the whole they survive, and this state of mind is a common fixture in certain East Asian societies.

Let us go on to the culture of conformity in East Asian societies. By “East Asians” this essay means, specifically, people shaped by the Confucian cultural sphere. We are in the habit of not expressing ourselves in public; sometimes even raising a hand to speak feels like enormous pressure. “Being the same as everyone else” may be one of the great survival habits, and after years upon years of socialization, trying to be the same as everyone else has become a knee-jerk reflex. Reading the air, as the Japanese put it, not being a bother to other people, even managing your own body odor: these all belong to the same cluster of concepts, the etiquette of taking up as little space as possible.

A culture of conformity like this does not even need top-down oppression to produce a kind of endogenous self-censorship all by itself. Before we put forward an unorthodox opinion, we run once through the whole tangle: will this sound abrupt, will other people fail to understand it, will it become a burden to them? That is self-censorship in its most basic form. And the ruler we measure with comes from a collective consciousness we imagine for ourselves. Although we call it collective consciousness, it is in fact tucked away separately inside each of us, so it might be more precise to define it as “the collective consciousness each individual privately supposes to exist.”

But precisely when everyone holds such a collective imagining, collectivity emerges. Let that collectivity iterate through enough behavior, trial, error and correction, and a dynamic collective consciousness is thereupon born, which may well be the origin point of conforming behavior. This is not the happy outcome that Benedict Anderson’s “imagined communities” are supposed to bring. We can of course call it an aggregate of national or cultural character, but on the darker reading, when self-consciousness willingly gives itself over to the collective consciousness, conformity makes people feel safe, without actually guaranteeing it, and at the same time makes them banal.

Timur Kuran’s “preference falsification” and Elisabeth Noelle-Neumann’s “spiral of silence” complete the loop. People hide their private beliefs because they anticipate sanction or fear isolation; public space therefore overestimates support for the mainstream opinion, which reinforces the silence further. Jonathon Penney’s research on Wikipedia browsing likewise shows that after government surveillance was widely reported, views of certain sensitive articles fell: a chilling effect can reach even perfectly legal reading (Penney, 2016).

This means that anyone trying to make their way in society carries the neural circuitry of self-censorship built in at every moment. Think before you speak, think before you raise your hand, think before you act. And if that self-censorship appears in an authoritarian or even totalitarian political environment, where top-down oppression exists purely to maintain a hegemonic culture, then self-censorship and collective censorship really do become one thing. Over time, people who self-censor may even develop a tendency toward system justification, forming a strength-worshipping culture that takes pride in its own hegemon. Even when the individual is coerced by power, holding only duties and no rights without knowing it, this subtle state of mind still emerges.

How can we tell easily whether a culture of conformity contains oppression from above? Perhaps we can bring in the eyeball test proposed by the political philosopher Philip Pettit. When you face different people, a partner, a peer, a family member, a boss, a politician, a law-enforcement agency, do you avert your eyes and turn your head away? If you do, there is a good chance that the other party ranks above you in the abstract world of power, which may indicate that you are in a relationship of domination. Let us ask the question another way: if you look at yourself in the mirror while thinking about an issue difficult enough that you might have to censor it, will you avoid your own eyes?

So within the culture of conformity in East Asian societies, an atmosphere of surveillance is born in which collective censorship and self-censorship resonate and reinforce each other, and hundreds of millions of people live inside this panopticon. Inside the great ring is a small ring: the great ring is the watcher who seeps through every crack, the small ring is the self-restraint that, as the Buddhist saying goes, the mind gives birth to on its own. When censorship becomes ordinary, argot and irony arise to meet it, and the Sinophone world may well have built the most formidable civilization of argot anywhere on earth.

Huddling Together for Warmth Against Collective Surveillance

We often see puzzling posts on Chinese-language social platforms, posts that make you go around the loop twice before you understand what the author is trying to say. Or rather, who the author is trying to say it to, and who they are trying to keep it from. This is exactly the art of argot.

The first reason is that saying things straight carries a clear risk, which creates the demand for argot. Keyword filtering, for instance, is an extremely efficient digital literary inquisition. When a user’s post contains a keyword the powerful would rather not see, the post is taken down, the account is annihilated, or, more heart-stopping still, the user is “invited to tea,” the euphemism for a summons from state security. As top-down control and an internet culture of collective censorship gradually take shape, censorship dictionaries are slowly built up. Users, of course, gradually feel out the boundaries of the censorship tools, work out the forbidden phrases, and then naturally develop argot or irony so that plain keyword filtering cannot bite.

For the past decade or so, the common method of online text censorship was plain keyword filtering: if the keyword appeared in the post, the post came down. In the last few years, though, the arrival of large language models has brought a rapid leap in the ability to analyze context and intent, and combined with existing tools such as stylometry, the magic weapons for fishing out a particular user have leveled up enormously.

The second reason is that argot makes it easy to tell friend from foe. Whoever understands it belongs to your tribe; whoever does not is an outsider. Argot, or irony, has to accumulate through shared lived experience. It is not something a centralized standard dictionary, an authoritative university lecturer or a news editor can define. Every generation, every region, every community is likely to have its own, and in a public space where everyone is jumping at shadows, the point of having argot matters more still.

Words themselves are double: exactly the same sentence has entirely different readings in different contexts, and nothing has been encrypted at all. A simple piece of argot can strengthen someone’s trust in a stranger, because whoever can speak it shares at least one stretch of culture, a line from a cartoon, an anime, a film or a song, a political event of great weight, or a meme that simply emerged. All of these can be birthplaces of argot, and none of them can be planned in advance.

James C. Scott called the performance of deference in front of power the “public transcript,” and the critique preserved behind power’s back the “hidden transcript.” Argot is precisely the gray channel between the two: it lets the hidden transcript enter semi-public space while preserving room to deny and retreat (Scott, 1990). King, Pan and Roberts, studying Chinese internet censorship, found that censorship targets content with collective-action potential in particular; what argot preserves is therefore not only room for expression but the ability to recognize comrades and coordinate action (King, Pan & Roberts, 2013).

Because double-meaning argot is not encrypted, anyone who puts in a little effort can pass as an insider quite easily; learn a few phrases and you can slip into the community. That is argot’s risk. But it is also why argot and irony develop so fast, fast enough that before the public has worked out whether someone supports or opposes a given position, whether they are being ironic or actually mean it, the evolving tribal code may already have shifted along another notch. At which point plenty of people inevitably think: “if it is this chaotic, I may as well give up trying to tell.” So more and more people lie flat, which can harden into rational ignorance and lead in turn to informational withdrawal and political disengagement.

But this is not comfortable lying flat; lying flat is not supposed to be this tiring. This particular inner journey toward lying flat is saturated with self-censorship. In a society full of digital literary inquisitions, citizens must consciously avoid certain places in order to escape disaster, and so their mental maps naturally sprout patch after patch of forbidden territory. This is lying flat saturated with self-censorship. To lie flat in genuine comfort, you have to untie the knots in your heart, smooth the mental map flat, and consciously undo the neural circuitry of the knee-jerk reflex.

There are two remedies here, one individual and one collective. On the individual side, you need to build digital hygiene habits without giving up on thinking. This does not require overdoing it: just put to work the atmosphere of constant conformity we already live in. Do not fall too far behind the group, and do not get too far ahead of it either, the old counsel of the mean. You will of course also need sound views on information security and privacy, and to judge, according to actual risk (your threat model), how far you really need to go. This is the way of living I call GrayPunk. The collective remedy is to make good-enough security practices the group default, so that not everyone has to keep up a high state of alert alone. The rest of this essay proceeds from there.

GrayPunk derives from cypherpunk, and the word cypherpunk borrows its name from cyberpunk. Cyberpunk works tend to imagine technological capability growing without limit while remaining pessimistic about civilization and its power relations. The future they depict is a human-machine composite in which class problems still exist and an extractive economy goes on plundering people and the environment; technology serves humans, but only the population at the top counts as human.

Cypherpunk took over cyberpunk’s name and tried to answer the dystopia it depicted with cryptography. Cypherpunk’s supporters lean anarchist; put bluntly, they do not much believe that governments, corporations or international organizations can guarantee an individual’s security. Security should begin with your own practice, including privacy tools and self-contained systems of exchange: currency, culture, language, network infrastructure and so on.

Cypherpunks are a very particular subcultural group, made up mainly of cryptographers, hackers with a will to political action, and academic circles. Few in number though they are, they have already become indispensable figures in the history of digital civilization, because they have won many battles in litigation against states and in the development of open-source technology, in the East as much as in the West. But there are plural value systems among cypherpunks too, the classic libertarian and the more left-wing spirit of solidarity, and plenty of each.

GrayPunk as a New Punk

But the GrayPunk this essay proposes does not require that kind of fervor, or that you be clever and hard-working, in order to join; it is a lay practice, not a monastic order. We might try peeling cypherpunk away from the Whig history that insists the world must eventually progress, and season it instead with the slacking spirit of lying flat. Perhaps a path of technological development like that is what actually moves civilization forward; who knows.

The Gray Man is a common term in operational security (OPSEC) and prepper communities. It means making yourself look ordinary in a crowd, unremarkable, not worth special attention, a common, low-cost strategy for hedging risk and countering surveillance. If a person is armed to the teeth, wearing a full set of high-end tactical gear and carrying specialized equipment, they may feel very safe, but in practice they have raised their own identifiability. The Gray Man’s reasoning runs the other way: blend into the environment, keep a low profile, make it hard for an observer to remember you and give them no reason to keep watching.

GrayPunk’s core spirit is not to develop an invisibility cloak beyond the world’s tech tree, but simply not to stand out from the crowd: to dim your light and mingle with the dust, as Laozi advised. This idea suits East Asian societies, which have spent whole lifetimes cultivating the spirit of conformity, extremely well, because to blend into a crowd you must be able to read a crowd, and the trick of self-censorship we have honed can be put to full use here, simply pointed in another direction. We know how to wear what everyone else is wearing, to go out and to raise a hand to ask a question at the right moment; we know how to get what we want without coming into conflict with anybody.

And still we know we are cool. That coolness is emphatically not external; no punk haircut, tattoos or nose ring required. The coolness is in the inner posture. We have our own punk spirit, tucked away beneath a gray coat, and this kind of coolness can find companions, and must have them. And because it is so much less difficult than cypherpunk, it can more easily reach a larger base, and more easily spread outward, slowly, from the niche, hard-to-implement layers of subculture.

What is more, a jump of an order of magnitude in numbers is itself the true practice of the cypherpunk spirit, because anonymity loves company. If real lying flat is to be achieved, then beyond individual security and daily habits, collective security is the second important subject. It is hard for one individual to compel others to cooperate in order to reach collective security; but if a whole society, or a whole tribe, adopts a set of not-so-difficult operating principles at the same time, path dependence will keep that set of principles alive inside the group for a very long time.

Even a society that runs on involution (neijuan, the East Asian word for competition that grinds everyone down without moving anyone forward), everyone trampling everyone else, still has a path toward safe lying flat. All it takes is for individuals to be consciously a little bit safer than the next person. We are all wearing gray, but when the predator comes hunting Gray Men, we have a few extra layers of protection and are more likely to slip through. People who think this way act, and over time the whole Gray Man community slowly upgrades its methods of protection, rather than balling up like a shoal of sardines and waiting for the sailfish to come and feed. We need to build second-order thinking into the development of technology and of digital literacy. Collective security is dynamic, and the best outcome is that the whole gradually levels up. That said, the long-run solution to this game cannot simply be to push risk onto more fragile people; it has to raise the overall security baseline step by step.

The history of the VPN illustrates exactly this kind of collective evolution, the kind the old proverb describes: the Way grows a foot taller and the demon grows ten. The VPN began as a rather boring piece of corporate information security: it let users outside the office connect safely into the company’s internal network through an encrypted tunnel. By the 2000s, open-source tools such as OpenVPN had gradually spread, and setting up your own encrypted tunnel had become easier and easier. At the same time, when China’s Great Firewall began carving up the network through DNS poisoning, IP blocking and keyword filtering, these tools, which had carried no revolutionary coloring at all, were quite naturally picked up to break through the block. The VPN at that point was very likely just something internet users reached for out of convenience, not a grand political act.

But the Great Firewall learns too. As more and more people used the same VPN tools, the traffic itself became an identifiable signature, so anti-censorship technology changed in turn. Shadowsocks, V2Ray and Tor’s various obfuscated transports were developed one after another, and the technical problem began shifting from plain encryption toward obfuscating traffic. Teams studying the Great Firewall found that since at least 2019, China’s censorship system has first used features such as packet length and entropy to guess whether a stream of traffic is Shadowsocks, then dispatched active probes to connect to the suspect server and confirm. By 2021 the Firewall had even begun identifying “fully encrypted” traffic at scale, affecting Shadowsocks, VMess and obfs4 alike. At this point, people using advanced technology look like soldiers in full battle rattle: once the outward appearance of your traffic departs from what a normal protocol looks like, it is very easily treated as an outlier.

So the development of obfuscation technology turned toward the Gray Man mode. The better the blockers get at hunting outliers, the more incentive anti-censorship tools have to imitate the normal, and the two sides co-evolve through round after round of identification, blocking, disguise and re-identification. The fight has already spread from protocols to regulations, app stores and commercial services, but the core is the same: the blocker looks for anomalies, and the user finds a way to melt back into normal traffic. Finn Brunton and Helen Nissenbaum call this kind of practice obfuscation, deliberately adding noise, ambiguity or plausible signals to make data harder to classify and exploit (Brunton & Nissenbaum, 2015).

This is also where GrayPunk is genuinely easy to put into practice. The grand ideal of internet freedom does not end in a landscape where everyone has become a cryptographer; it may end with millions of people acquiring an utterly ordinary habit. When censorship levels up a little, the tools level up a little too; when the tools get too hard to use, somebody in the market finds a way to repackage them a little more simply. Every individual only needs to know a little more than they did yesterday. That is already pretty punk.

GrayPunk, then, is collective security, and collective security is hiding a tree in the forest. Across the long river of history we assume there is no natural predator of humans that will wipe out humanity in one go, only humans competing with each other, and so while there is no guarantee that every tree stays standing, the whole forest is hard to clear at a single stroke.

So when we discuss collective security we must take into account the art of non-resistance and the courage to coexist; after all, that is what life actually looks like. Conforming, self-censoring, living comfortably, being a little bit safer than the next person while also being a little bit cool: that spirit has lived in us for a long time already. In East Asian societies, cypherpunk is not necessarily a pure ideological ideal; it is a precondition for survival.

Why Cypherpunk Never Went Mainstream, and How It Might Turn

Look across the history of the internet and cypherpunk has plainly won a number of beautiful victories: private communication (E2EE), anonymous networking (Tor), digital signatures (PGP and its descendants), electronic money (Bitcoin, Ethereum, Monero, Zcash), ideas that have long since sunk deep into digital civilization. So why has cypherpunk remained stuck in a subcultural layer with few members and a very high barrier to entry?

More precisely, what struggles to go mainstream is cypherpunk as a self-aware political identity and way of life. The technologies cypherpunk created often do enter the mainstream, just wearing a different face. Once a tool truly spreads, people no longer need to understand its history, its ideology or its technical details; it takes off the punk leather jacket and becomes the default, by default. Users are protected by it every day without necessarily knowing where the protection came from. This may be exactly where cypherpunk is most successful and, at the same time, hardest to see.

What is cypherpunk, exactly? In “A Cypherpunk’s Manifesto,” published in 1993, Eric Hughes understood privacy as the power to selectively reveal oneself to the world. The individual cannot expect governments, corporations and other vast organizations to grant privacy out of goodwill, and so must build, together with others, systems capable of anonymous transactions and private communication. Cypherpunk’s best-known creed is the line “Cypherpunks write code”: a political position has to be realized as a technical tool, or it is just talk.

This gives cypherpunk the character of prefigurative politics. It does not merely make demands of existing institutions; it also tries to write a small part of the ideal order into the protocol in advance. Institutional design of this kind is in fact a rather left-wing imagining, because before the code, as before the law, everyone is equal. The approach replaces waiting for permission with building, and carries an egalitarian imagination; yet the formal equality the code provides can still be canceled out by inequalities of resources, capability and infrastructure, and so code, as an actor in a social movement, is caught in a dynamic loop. When petitions ask the powerful not to surveil the people, cypherpunk tries to make surveillance technically harder. When the law asks a government to respect freedom of speech, cypherpunk tries to build communication systems that no single government can easily shut down. When people ask a platform to treat its users well, cypherpunk tries to preserve the ability to export your data, start over elsewhere and leave the platform.

But the early cypherpunks sometimes also carried a strong technological inevitabilism. So long as cryptography kept developing and code kept spreading around the world, power, it seemed, would eventually be tamed by technology. That slides easily back into the Whig history criticized earlier in this essay, as though the tech tree had only one direction and every branch eventually led to freedom.

Reality is obviously messier. The same cryptography that protects dissidents also protects ransomware; the same distributed network that supports public collaboration can once again let a handful of nodes, exchanges and service providers monopolize it. Technology will not choose civilization’s direction for us on its own.

Technology clearly will not stop accelerating, then, but we can choose the direction of the acceleration. The decentralized accelerationism (d/acc) proposed by Vitalik Buterin can be read as an update to the cypherpunk spirit. The full sense of d/acc is “decentralized and democratic differential defensive acceleration,” where the d points at once to decentralization, democracy, differential and defensive. It acknowledges that technological development brings enormous benefits, and acknowledges too that technological stagnation can cause real harm, but accelerating technology should not be understood as flooring the pedal without a word of discussion. Different technologies shift the balance of power between attacker and defender, and so we must give priority to developing the technologies that make attack harder, recovery easier and power more distributed.

Defense here is not the same as waiting passively, nor the same as handing all power to a prophet who claims to be able to protect the public. What d/acc pursues is distributed defense: individuals, communities and local organizations each holding a degree of protective capability, so that when the system is attacked it does not collapse entirely because a single node has fallen, and ordinary people do not have to permanently surrender their data, their identity and their freedom of action in order to obtain security. A sovereign whose word cannot be trusted is, after all, the largest security hole of them all.

This kind of thinking pushes cypherpunk one step onward, from personal privacy to collective security and even to the defense of civilization. Encrypted communication protects a conversation between two people; information defense protects a whole society’s capacity for judgment. Multisig protects one person’s holdings; institutional checks, balances and resilience mechanisms protect an organization from single points of failure. What is being protected expands gradually from the hacker, the punk who, in Mencius’s phrase, looks after their own virtue alone, outward to communities, organizations, public health, the information environment and democratic institutions.

Seen this way, the truly important function of defensive technology is not necessarily to make the strongest people invulnerable. Its more important function is to reduce the fragility of ordinary people, so that after one upheaval and then another they still keep the chance to get up again. This connects precisely with what this essay calls lying flat while keeping your edge: the posture of security is not standing permanently on guard, but being able to lie flat with your mind at ease.

In 2026, the Ethereum Foundation, in its Mandate, organized the core principles it must uphold into CROPS: Censorship Resistance, Open Source, Privacy and Security. The Mandate places these principles above convenience in priority and treats them as non-negotiable. It goes on to propose that the way self-sovereignty is used must be able to resist extraction while also offering a seamless user experience.

“Seamless” matters especially. The cypherpunk community has long been prone to treating unusability as the price freedom must pay, but a self-sovereignty tool that only experts can operate safely offers no more than a formal choice. Ordinary people will end up handing their keys, data and judgment back to an intermediary anyway, because daily life has no room for a full-time ascetic practice of information security. Designers cannot ask users to endure a terrible interface forever in order to defend a principle. On the contrary, designers must work to make censorship resistance, open source, privacy and security ordinary enough that ordinary people can go on being protected without renewing their vows every day. Only then can ordinary people join the ranks of the Gray Men.

I once proposed the idea of a Defense Transformation Guide, an attempt to offer a set of everyday methods for moving toward self-sovereignty and collective solidarity. When we talk about digital transformation today, society seems to suffer from neophilia; it likes to reward the people who invent new things. People like new platforms, new protocols, new artificial intelligence, new governance models and new startups, and they like watching founders wander around with a hammer looking for nails. As for maintenance? That is an afterthought nobody cares about. But as d/acc puts it, the axis of technological development can in fact be steered collectively by a population, and so I have been looking, in the space between collective solidarity and individual self-sovereignty, for the cypherpunk-rooted technologies and the latent next-generation techniques that belong there.

In the course of gathering and classifying these technologies, I found that cypherpunk still is not mainstream. There are many reasons; let us take them one at a time.

i. If It Isn’t Radical, It Isn’t Cool

A subculture needs to be a minority, but security needs to be collective. A large part of what makes punk cool is its distance from mainstream society. Once everybody can do a thing, it struggles to go on serving as a badge of identity. This leaves cypherpunk with an internal contradiction: it wants more people using privacy tools, but as soon as the tools spread, the special identity that came with the tools loses its value.

Inside a subculture, difficult knowledge, rare tools, special language and a high cost of practice can all become a form of subcultural capital. In cypherpunk, someone who runs their own server, verifies software signatures, knows how to compile code and is fluent in anonymous network protocols is of course worth admiring. But when those same skills are also used to prove who is cooler, technical ability hardens into rank within the community.

Argot cuts both ways here too. In an oppressive environment, argot helps comrades recognize each other and dodge crude text censorship; once it enters a technical community, it can turn into a gatekeeping mechanism. A newcomer who does not know what a seed phrase, entropy, a key or obfuscation means will struggle to take part in the conversation. This is particularly dangerous for information security. Security requires people willing to admit they do not understand something, and willing to admit they have been scammed before. The identity boundary originally used to recognize comrades can also get in the way of genuine mutual aid.

Cypherpunk communities are also prone to disputes over orthodoxy, over who is the true ascetic. Using that operating system is not secure enough; keeping data on that cloud is not independent enough; not self-hosting a node is not decentralized enough; still using mainstream social platforms is not resistant enough. Each criticism looks reasonable on its own, but add them together and the only qualifying cypherpunks left are the handful of people who can pour in vast amounts of time, money and specialist knowledge.

When a tool requires the user to complete an identity conversion and accept an entire worldview before they qualify for basic protection, it will struggle to enter the daily life of wage cattle. This gives cypherpunk a perverse incentive: the community most readily rewards whoever is furthest out in front, and does not necessarily reward whoever makes existing technology more boring, more stable and easier to use. Inventing a new protocol is cool; writing the missing documentation for an old protocol is less cool. Proposing the most extreme threat model is cool; working out a good-enough configuration for ordinary people is less cool. Declaring every mainstream platform unusable is cool; designing a path that lets users migrate gradually is less cool. But technological diffusion usually depends on that second, less cool kind of work.

ii. Security Fatigue

The second reason cypherpunk cannot go mainstream is security fatigue. As the previous section said, ordinary people cannot become paragons. A perfect cypherpunk needs a password manager, hardware security keys, encrypted drives, anonymous networking, an independent email service, separate identities for separate purposes, end-to-end encrypted messaging, offline backups and self-hosted services. They have to update software regularly, audit permissions, verify downloaded files, rotate keys and rehearse their recovery procedure, and to watch at every moment for locations showing up in their photos, metadata left behind in their documents, and whether their browser has formed a unique fingerprint.

NIST describes security fatigue as the weariness and resistance people develop when facing computer security. When warnings, password rules and security decisions come too frequently, people easily feel powerless, and go on to ignore the warnings and adopt riskier behavior. The heart of this problem is not that users lack knowledge; many have simply been bombarded for years by security demands beyond their cognitive load.

The design emphasis of low-friction security, then, is not only on educating the user but on reducing the number of security decisions the user has to remember, judge and repeatedly carry out. Tactical Tech’s Holistic Security places digital, physical, organizational and psychosocial security inside a single framework. A security regime that exhausts the people practicing it cannot last.

iii. You Can’t Lie Flat Without Money

The third reason cypherpunk cannot become mainstream is that maintaining technology takes resources. Open source can be distributed for free, but continuous maintenance still has to be paid for, and a surprising number of open-source projects critical to the world are maintained by one or two volunteers. The world has now reached the era in which these volunteers of the networked world are withering away, one by one, for reasons of health. Once a maintainer burns out, falls ill or leaves, an entire ecosystem can be exposed to risk. Steven Jackson’s “broken world thinking” warns us that technological order continues mainly through repair, care and maintenance; this work is less conspicuous than inventing a new protocol, but it decides whether a system lives (Jackson, 2014).

Privacy tools also face a peculiar commercial predicament. A lot of free consumer technology profits by collecting user data, serving ads and predicting behavior, but a service that protects privacy would collide with its own mission if it adopted the same model. Signal has explained publicly that maintaining a global private-communication service requires enormous infrastructure and development spending, and that the surveillance business model has spent years leaving users with the mistaken impression that consumer technology ought naturally to be free. Commercialization is not inherently a betrayal. The real question is whether the source of revenue is aligned with the user’s security. Subscriptions, cooperatives, public procurement, foundation grants, paid technical support, cross-subsidy and public-goods funding could all be remedies.

And making security the default itself requires steady funding, maintenance and documentation work.

The security technologies that have genuinely gone mainstream in history have usually completed one act of de-ritualization.

The spread of HTTPS did not depend on every website administrator in the world becoming a cryptographer. Let’s Encrypt lowered the cost of deployment with a free, automated and open certificate service, and the ACME protocol made requesting and renewing certificates something that could be automated at scale. In 2020 Let’s Encrypt issued its billionth cumulative certificate, and it treated usability and automation directly as the essential foundations of that diffusion. End-to-end encrypted messaging entered ordinary life without billions of people first understanding key exchange. In 2016 WhatsApp made end-to-end encryption the default state for calls and messages; users did not have to switch encryption on, and did not even have to know encryption was happening.

Together these cases show that technology rarely enters the mainstream because everyone has accepted a complete political philosophy. It enters the mainstream because the cost fell, the operations vanished, and the setting became the default. Cypherpunk technology’s most successful moments are usually also the moments when it looks least like cypherpunk. Every day, our connections, conversations and devices are already protected by those ideas. The revolution is absorbed by the establishment, and that, perhaps, is what technology actually reproducing looks like.

iv. The Ant Cannot Shake the Tree

The fourth reason cypherpunk cannot become mainstream is the extreme asymmetry of power. One developer can invent a new anti-censorship protocol, but the state holds far more power at the same time. The VPN history recounted above has already shown that this is a co-evolution with no endgame. If what cypherpunk imagines is one beautiful technical counter-kill, reality will usually disappoint. States and large platforms can lose a round, but as the old saying goes, a hundred-legged centipede does not stiffen the moment it dies; they will not fall apart on their own any time soon.

But an ant does not necessarily have to push a tree over head-on, and a forest does not survive on any single tree. A forest’s resilience comes from the symbiotic relationships between different species. Part of what stands above ground may be felled while the root system below still holds the ability to grow back. The real goal of anti-censorship technology, therefore, is not necessarily to destroy the censor in one blow. It can be to keep raising the cost of total control, to preserve alternative channels, to slow the lock-in of power, and to make sure knowledge and relationships do not disappear along with any single tool.

A single tool is easy to target; an ecosystem can turn, change shape and regenerate. This is precisely why GrayPunk must emphasize collective security. No individual needs the capability to defeat a state, but the group as a whole needs to avoid betting all its hope on one prophet, one paragon.

These four reasons are in fact interlocked. Subcultural boundaries obstruct diffusion, excessive operating costs obstruct practice, a lack of resources obstructs maintenance, and asymmetry of power makes it hard for any single victory to become a permanent result. The remedy must therefore lower the cost of identity, the cost of operation, the cost of maintenance and the cost of confrontation all at once. Cypherpunk needs to shift gradually from a heroic narrative into daily life, from the extreme security of a few paragons to the proportionate security that most ordinary people can sustain over the long run.

GrayPunk as a Fashion

The most interesting thing about fashion is that people usually imitate first and understand afterward. Most people do not read a whole history of clothing, a course in textiles and a body of identity politics before deciding what to wear today. They watch the people around them, see that some practice looks convenient and good, and adopt it. Fashion is therefore a low-cost mechanism of group coordination. It does not require every participant to share a complete theory; it only requires that a practice have a low enough threshold for imitation.

This is exactly what lets us repurpose the conformity nerve of East Asian societies.

Conformity originally taught people to read the air, censor themselves and avoid standing out; GrayPunk tries to turn that same capability toward collective security. When the people around you all use a password manager, turn on a device passcode, update regularly, use encrypted messaging and cut back unnecessary permissions, the individual does not have to feel they are taking part in a revolution. They are only doing what everyone else is doing.

GrayPunk has no uniform. If a particular set of signs were required, that aesthetic would already have lost the gray coat’s function. GrayPunk can have a shared posture, but it should not fix that posture into something easily recognized. GrayPunk is fluid. It spreads more the way a habit spreads than the way a costume does. GrayPunk is therefore a subculture without a subcultural uniform. It keeps punk’s distrust of power, its insistence on autonomy and its imagination of alternative systems. Its coolness is hidden where you cannot see it at first glance.

Laziness, besides, is also a fashion. The laziness meant here is a long way from negligence. Negligence is knowing the risk and leaving the problem to your future self; lazy design demands that the system handle the repetitive, trivial and error-prone work in advance. GrayPunk therefore treats laziness as a formal engineering specification. Important choices should appear at the moments that genuinely carry meaning, and the rest of the work should be borne by tools, organizational norms and infrastructure. If security only holds when you are alert, have plenty of time and are running high on political passion, then it is not security fit for human society.

Cool is where you cannot see it at first glance.

GrayPunk’s coolness can be measured in a counterintuitive way. The less a security technology demands the user’s attention to itself, and the more it preserves the user’s autonomy at the same time, the closer it comes to GrayPunk. The best protection is usually like the fire piping inside a building: nobody photographs it or checks in beside it on an ordinary day, but when the fire comes it decides who gets out of the building alive.

GrayPunk nevertheless faces one supremely important ethical question: if you lower your identifiability, does that steer you back toward self-erasure? Would it dissolve a subcultural group’s agency to advocate at all? The question is especially sharp in East Asian societies. If all we are doing is repackaging silence, obedience and the loss of one’s edges as a gray-coat strategy, that is already proof that power has won. Self-censorship does not become liberation automatically just because it has put on a punk name.

The difference between the gray coat and self-erasure can be identified through three tests: choice, reversibility and reciprocity.

The first is choice. Who exactly decides that a person should keep a low profile? If the answer is a boss, a government, a family, community opinion or internalized fear, then it is closer to coerced self-censorship. If the individual can still decide to whom, when and how much to disclose, then low visibility becomes part of privacy. This returns us to Eric Hughes’s understanding of privacy: the core of privacy is keeping the choice of whether to reveal oneself.

The second is reversibility. The gray coat should be a coat you can put on and also take off. An individual keeping a low profile in a high-risk environment should still preserve their name, their memories, their views, their relationships and their capacity to act inside the spaces they trust. They can tell the truth in the kitchen, they can recognize and be recognized among comrades, they can leave testimony when the conditions are right, and they can walk back into public space when they must. A strategy of invisibility you can never exit is more wretched than the panopticon.

The third is reciprocity. Does the gray coat make the whole forest denser, or does it only get you behind somebody else? If an individual shifts risk onto people who are more conspicuous, poorer or less technically capable, that is still a competitive hedge. GrayPunk instead requires that an individual’s protection create a public spillover, making it easier for other people to get secure too. A real anonymity set cannot be built alone, and truly hiding a tree in the forest cannot mean hiding yourself while cutting down every tree around you.

This also echoes the eyeball test mentioned earlier. The gray coat does not ask people to keep their heads down forever; it asks them to preserve the ability to choose when to raise them. Real security is not making a person never dare to look power in the eye again; it is that when they decide to look, there is still a group behind them that will not vanish the instant they fall for a while. In Albert Hirschman’s language, the gray coat can be a limited exit: lowering exposure for now while preserving the capacity for voice later.

Nor does GrayPunk demand that everyone lying flat suddenly stand up. Those who lie flat can take part at low intensity. A person may be unwilling to become a public political activist, but they can live more safely; they can back up data, maintain documentation, fund infrastructure, and teach the people around them to use mature tools. This low-visibility maintenance work is itself part of collective security.

In Closing: How to Be a Lazy Cypherpunk

Having written this far: being a lazy cypherpunk does not actually require imagining yourself as the last member of the resistance, nor saving up for a bunker while you wait for the end of the world.

We should lie flat in order to win lying down.

Winning lying down, the gamer’s term for a victory your teammates carry you to, means stretching the confrontation into an endurance race. The opponent has to keep pouring resources into surveillance, identification, blocking and pursuit, while we fold security into ordinary life so that each evasion costs a little less and each recovery comes a little faster. When the controller’s cost of “stability maintenance,” to use the Chinese state’s own term, keeps rising, and the controlled need only preserve enough slack to avoid being fully controlled, lying flat can turn into an asymmetric advantage.

A warrior does not need full battle rattle to go and buy breakfast. Security should observe proportion too, and this can be called proportionate security. Strapping on every protective tool you can find will not necessarily make you safer, and may well give the game away, exposing your own peculiarity while producing psychological fatigue on top.

The lazy cypherpunk also needs a little security zen. Security zen means taking in new knowledge, practicing with tools that have already matured, and reviewing your own life regularly, without falling into panic over every piece of security news. Do not mistake anxiety for diligence, or complexity for security. A genuinely deep security practice often shows up as a handful of actions so ordinary they are disappointing.

This is also a game of being a little bit safer than the next person. In the short run, a bit more protection lowers your chance of being the easiest target to attack; over a longer horizon, the most stable strategy is still to raise the security baseline for more people together. Anonymity loves company: the fewer people using a given privacy tool, the more the act of using it becomes a fingerprint in itself, and only when there are enough users does it blend into the ordinary background. We can borrow the metaphor of k-anonymity here: when a person shares their visible features with enough other people, they are harder to single out. A single Gray Man cannot make a GrayPunk community.

So what we have to do is not to forge ourselves into tireless paragons. The GrayPunk sidesteps heroic martyrdom and also refuses numb surrender. They choose a way of living that can be kept up through being busy, being tired, being dumped, being laid off, being ill and living through a political winter. A genuinely reliable security habit has to still work on the days when a person has the least strength; a genuinely reliable collective has to keep running after one or two people have fallen.

The social-movement scholar Verta Taylor calls the state in which a movement preserves its organization, its relational networks and its collective identity through an ebb tide “abeyance,” which might be rendered as holding in latency (Taylor, 1989). Lying flat while keeping your edge can be read as this concept’s version for digital survival, or, going one step further, as a description of the state of mind of an indestructible, indolent activist.

Lying flat while keeping your edge is king, because only a sustainable life makes for a long resistance. Lie down comfortably, keep the system running, and stay in the same forest as your companions: that is the most sustainable posture available to a lazy cypherpunk.

GrayPunk is the first essay of Telescope Editions, Parity's essay grant. Text © 2026 Yen-Lin (mashbean) Huang, published under CC BY-SA 4.0.