The high-stakes race to make quantum computers work - Chiara Decaroli

譯者: Lilian Chiu 審譯者: Bruce Sung

The contents of this metal cylinder could either revolutionize technology

這個金屬圓柱的內容， 可能可以帶來技術革命，

or be completely useless—

也可能完全沒用處——

it all depends on whether we can harness the strange physics of matter

這全都要看我們能否 在非常非常小的尺度上

at very, very small scales.

利用物質的奇特物理性質。

To have even a chance of doing so,

若要有機會能夠這麼做，

we have to control the environment precisely:

首先我們必須要能精準控制環境：

the thick tabletop and legs guard against vibrations from footsteps,

用很厚的桌面和桌腳對抗震動，

來自腳步、附近電梯 和開關門等等的震動。

nearby elevators, and opening or closing doors.

The cylinder is a vacuum chamber,

這個圓柱是個真空腔體，

devoid of all the gases in air.

沒有空氣中的任何氣體。

Inside the vacuum chamber is a smaller,

在真空腔體中 有個較小、極冷的隔間，

extremely cold compartment, reachable by tiny laser beams.

用非常小的雷射光束可以到達。

Inside are ultra-sensitive particles that make up a quantum computer.

裡面有特別敏感的粒子， 用來製作量子電腦。

So what makes these particles worth the effort?

是什麼讓這些粒子 值得這麼大費功夫？

In theory, quantum computers could outstrip the computational limits

理論上，量子電腦可以超越

傳統電腦的計算限制。

of classical computers.

Classical computers process data in the form of bits.

傳統電腦處理資料時， 用的是位元的形式。

Each bit can switch between two states labeled zero and one.

每一個位元會在兩種狀態中切換， 這兩種狀態被標為 0 和 1。

A quantum computer uses something called a qubit,

量子電腦用的是量子位元，

which can switch between zero, one, and what’s called a superposition.

它可以在 0、1， 及所謂的疊加之間切換。

While the qubit is in its superposition,

當量子位元在疊加狀態時，

it has a lot more information than one or zero.

它所具有的資訊遠超過 0 或 1。

You can think of these positions as points on a sphere:

可以把這些位置視為球體上的點：

the north and south poles of the sphere represent one and zero.

球體的北、南極代表 1 和 0。

A bit can only switch between these two poles,

位元只能在兩極之間切換，

but when a qubit is in its superposition,

但當量子位元疊加時，

it can be at any point on the sphere.

它能在球體上的任何位置。

We can’t locate it exactly—

我們無法精確地定位它——

the moment we read it, the qubit resolves into a zero or a one.

當我們讀量子位元時， 它就會拆解為 0 或 1。

But even though we can’t observe the qubit in its superposition,

儘管我們無法觀察疊加的量子位元，

we can manipulate it to perform particular operations while in this state.

我們能夠操控它，讓它在 這個狀態中執行特定的工作。

So as a problem grows more complicated,

所以，遇到更複雜的問題時，

a classical computer needs correspondingly more bits to solve it,

傳統電腦需要相對 更多位元來解決它，

while a quantum computer will theoretically be able to handle

而理論上量子電腦 可以處理更複雜的問題，

more and more complicated problems

without requiring as many more qubits as a classical computer would need bits.

傳統電腦需要許多額外的位元， 量子電腦卻不用那麼多量子位元。

The unique properties of quantum computers

量子電腦獨特的特性

result from the behavior of atomic and subatomic particles.

源於原子和亞原子的粒子行為。

These particles have quantum states,

這些粒子的量子狀態

which correspond to the state of the qubit.

對應到量子位元的狀態。

Quantum states are incredibly fragile,

量子狀態非常脆弱，

easily destroyed by temperature and pressure fluctuations,

容易被溫度和壓力的波動、

stray electromagnetic fields,

雜散電場，

and collisions with nearby particles.

以及附近相撞的粒子所摧毀，

因而量子電腦需被精心設定。

That’s why quantum computers need such an elaborate set up.

It’s also why, for now,

正因如此，截至目前為止

the power of quantum computers remains largely theoretical.

量子電腦仍主要是理論上具有力量，

So far, we can only control a few qubits in the same place at the same time.

在同一時間、同一位置 只能控制少數幾個量子位元。

There are two key components involved

想要有效地管理 這些無常的量子狀態，

in managing these fickle quantum states effectively:

涉及到兩項關鍵要素：

the types of particles a quantum computer uses,

量子電腦所使用的粒子類型，

and how it manipulates those particles.

以及它如何操控這些粒子。

For now, there are two leading approaches:

現在有兩種主要的方法：

trapped ions and superconducting qubits.

囚禁離子和超導量子位元。

A trapped ion quantum computer uses ions as its particles

囚禁離子量子電腦 會把離子當作其粒子來使用，

and manipulates them with lasers.

並用雷射來操控它們。

The ions are housed in a trap made of electrical fields.

離子會被放置在 電場製成的陷阱中。

Inputs from the lasers tell the ions what operation to make

來自雷射的輸入會造成 量子位元狀態在球體上轉動，

by causing the qubit state to rotate on the sphere.

來告訴離子要做什麼工作。

To use a simplified example,

用個簡化的例子來說明，

the lasers could input the question:

雷射可以輸入這個問題：

what are the prime factors of 15?

15 的質因數有哪些？

In response, the ions may release photons—

回應時，離子可能會釋出光子——

the state of the qubit determines whether the ion emits photons

量子位元的狀態 決定離子是否要釋出光子

and how many photons it emits.

和釋出多少光子。

An imaging system collects these photons and processes them to reveal the answer:

成像系統收集這些光子， 處理它們，揭示答案：

3 and 5.

3 和 5。

Superconducting qubit quantum computers do the same thing in a different way:

超導量子位元量子電腦 用不同的方式做同樣的事：

using a chip with electrical circuits instead of an ion trap.

用電路晶片取代離子陷阱。

The states of each electrical circuit translate to the state of the qubit.

每個電路的狀態會被翻譯成 量子位元的狀態。

They can be manipulated with electrical inputs in the form of microwaves.

可輸入微波形式的電子來操控它們。

So: the qubits come from either ions or electrical circuits,

所以，量子位元來自離子或電路，

acted on by either lasers or microwaves.

被雷射或微波操控。

Each approach has advantages and disadvantages.

兩種方法各有利弊。

Ions can be manipulated very precisely,

離子的操控精確而且持久，

and they last a long time,

but as more ions are added to a trap,

但當陷阱中的離子越來越多，

it becomes increasingly difficult to control each with precision.

就越來越難以精確地控制各個離子。

We can’t currently contain enough ions in a trap to make advanced computations,

我們目前還無法在一個陷阱中 放入足夠的離子來做進階的計算，

but one possible solution might be to connect many smaller traps

但有一個可能的解決方案： 改成連結許多較小的陷阱，

that communicate with each other via photons

這些較小的陷阱會透過 光子來和彼此溝通，

rather than trying to create one big trap.

這做法可以取代單個大陷阱。

Superconducting circuits, meanwhile, make operations much faster than trapped ions,

超導電路的運作速度 比囚禁離子快很多，

and it’s easier to scale up the number of circuits in a computer

而且，在電腦中增加電路的數目

會比增加離子的數目容易。

than the number of ions.

But the circuits are also more fragile,

但其電路比較脆弱，

and have a shorter overall lifespan.

整體的壽命也比較短。

And as quantum computers advance,

隨著量子電腦進步，

they will still be subject to the environmental constraints

它們仍然會受制於

needed to preserve quantum states.

保存量子狀態所必要的環境限制。

But in spite of all these obstacles,

儘管有上述這些障礙，

we’ve already succeeded at making computations

我們已經成功在一個我們無法進入

in a realm we can’t enter or even observe.

甚至無法觀察的領域中進行計算。