A beginner's guide to quantum computing | Shohini Ghose

譯者: Lilian Chiu 審譯者: Wilde Luo

Let's play a game.

咱們來玩個遊戲。

Imagine that you are in Las Vegas,

想像你在拉斯維加斯，

in a casino,

在一間賭場裡，

and you decide to play a game on one of the casino's computers,

你決定在其中一台電腦上玩遊戲，

just like you might play solitaire or chess.

就像是玩紙牌或是下棋。

The computer can make moves in the game, just like a human player.

電腦也能移動遊戲中的棋子， 和人類玩家一樣。

This is a coin game.

這是一個硬幣遊戲。

It starts with a coin showing heads,

一開始，有一枚正面朝上的硬幣，

and the computer will play first.

開局後，電腦先玩。

It can choose to flip the coin or not,

它可以選擇是否拋擲這枚硬幣，

but you don't get to see the outcome.

但你不會知道結果如何。

Next, it's your turn.

接著就輪到你。

You can also choose to flip the coin or not,

你也可以選擇是否拋擲這枚硬幣，

and your move will not be revealed to your opponent, the computer.

你的對手，也就是電腦， 同樣不會知道這一輪的結果。

Finally, the computer plays again, and can flip the coin or not,

最後，又輪到電腦 選擇是否拋擲硬幣，

and after these three rounds,

經過三輪遊戲之後，

the coin is revealed,

硬幣的狀態被揭示出來，

and if it is heads, the computer wins,

如果是正面朝上，就是電腦贏，

if it's tails, you win.

如果是反面朝上，就是你贏。

So it's a pretty simple game,

這是個很簡單的遊戲，

and if everybody plays honestly, and the coin is fair,

如果大家都不作弊， 且硬幣也是均勻的，

then you have a 50 percent chance of winning this game.

那麽你就有 50% 的機會獲勝。

And to confirm that,

為了確認這一點，

I asked my students to play this game on our computers,

我讓我的學生用我們的 電腦來玩這個遊戲，

and after many, many tries,

在嘗試非常非常多次之後，

their winning rate ended up being 50 percent, or close to 50 percent,

他們的勝率最後是 50% 或接近 50%，

as expected.

和預期的一樣。

Sounds like a boring game, right?

聽起來很無聊，對吧？

But what if you could play this game on a quantum computer?

但如果你能用量子電腦 來玩這個遊戲，會怎樣？

Now, Las Vegas casinos do not have quantum computers,

拉斯維加斯的賭場可沒有量子電腦，

as far as I know,

據我所知是這樣，

but IBM has built a working quantum computer.

但 IBM 已經打造出了一台 能夠正常運轉的量子電腦。

Here it is.

就是它。

But what is a quantum computer?

但是，量子電腦是什麼？

Well, quantum physics describes

嗯，量子物理是在描述

the behavior of atoms and fundamental particles,

原子和基本粒子的行為，

like electrons and photons.

比如電子和光子。

So a quantum computer operates

所以，量子電腦的運作方式 在於控制這些粒子的行為，

by controlling the behavior of these particles,

but in a way that is completely different from our regular computers.

但其做法和普通的電腦完全不同。

So a quantum computer is not just a more powerful version

量子電腦並不只是

我們目前電腦的加強版，

of our current computers,

just like a light bulb is not a more powerful candle.

就好像電燈泡並不是加強版的蠟燭。

You cannot build a light bulb by building better and better candles.

無論如何，蠟燭也不可能變成電燈泡。

A light bulb is a different technology,

電燈泡使用了一種不同的技術，

based on deeper scientific understanding.

它的基礎是更深入的科學理解。

Similarly, a quantum computer is a new kind of device,

同樣地，量子電腦也是一種新裝置，

based on the science of quantum physics,

以量子物理為根據，

and just like a light bulb transformed society,

就如同電燈泡改變了人類社會，

quantum computers have the potential to impact

量子電腦也有潛力影響 我們生活的方方面面，

so many aspects of our lives,

including our security needs, our health care and even the internet.

包括我們的安全需求、 我們的醫療保健，甚至網際網路。

So companies all around the world are working to build these devices,

全世界的公司都在打造這類裝置。

and to see what the excitement is all about,

要想看看它有多讓人興奮，

let's play our game on a quantum computer.

咱們來用量子電腦玩這個遊戲。

So I can log into IBM's quantum computer from right here,

我可以從這裡登入到 IBM 的量子電腦，

which means I can play the game remotely,

也就表示我可以從遠端玩這個遊戲，

and so can you.

你也可以做到。

To make this happen, you may remember getting an email ahead of time, from TED,

為了讓你們參與進來，你們可能記得，

先前有收到 TED 寄的電子郵件，

asking you whether you would choose to flip the coin or not,

信上請你選擇， 如果你在玩這個遊戲，

是否會選擇拋擲硬幣。

if you played the game.

Well, actually, we asked you to choose between a circle or a square.

事實上，我們在信上 是請你選擇圓形或方形。

You didn't know it, but your choice of circle meant "flip the coin,"

你當時並不知道，選擇圓形 就表示「擲硬幣」，

and your choice of square was "don't flip."

選擇方形就表示「不要擲」。

We received 372 responses.

我們收到了 372 個人的回覆。

Thank you.

謝謝你們。

That means we can play 372 games against the quantum computer

那就表示，我們可以用你們的選擇，

跟量子電腦玩 372 場遊戲。

using your choices.

And it's a pretty fast game to play,

這個遊戲一下就結束了，

so I can show you the results right here.

所以我可以把結果呈現在這裡。

Unfortunately, you didn't do very well.

不幸的是，你們的戰績不太好。

(Laughter)

（笑聲）

The quantum computer won almost every game.

量子電腦幾乎全勝。

It lost a few only because of operational errors in the computer.

它輸了幾場，只是因為 電腦中的運算錯誤。

(Laughter)

（笑聲）

So how did it achieve this amazing winning streak?

所以，它是如何取得 這驚人的一連串勝利的？

It seems like magic or cheating,

它就像魔術或作弊一樣，

but actually, it's just quantum physics in action.

但事實上，它只是量子物理的運作。

Here's how it works.

它的運作方式如下。

A regular computer simulates heads or tails of a coin as a bit,

普通電腦用一個位元來 模擬硬幣的正反面，

a zero or a one,

即 0 或是 1，

or a current flipping on and off inside your computer chip.

或記錄當前是否選擇拋擲硬幣， 儲存在你的電腦晶片中。

A quantum computer is completely different.

量子電腦則完全不同。

A quantum bit has a more fluid, nonbinary identity.

一個量子位元更具有 不固定性、非二進制的特質。

It can exist in a superposition, or a combination of zero and one,

它能存在於量子疊加態當中， 即 0 和 1 的組合當中，

with some probability of being zero and some probability of being one.

既有可能是 0，也有可能是 1。

In other words, its identity is on a spectrum.

換言之，它的真面目其實是一個範圍。

For example, it could have a 70 percent chance of being zero

比如，它可能有 70% 的概率是 0，

and a 30 percent chance of being one

30% 的概率是 1，

or 80-20 or 60-40.

或 80% 與 20%， 60% 與 40%等。

The possibilities are endless.

存在無限的可能性。

The key idea here

這裡的關鍵在於，

is that we have to give up on precise values of zero and one

我們得要捨棄「只存在固定的 0 和 1」 的思考方式，

and allow for some uncertainty.

允許不確定性存在。

So during the game,

在遊戲期間，

the quantum computer creates this fluid combination of heads and tails,

量子電腦會創造出正反兩面 （0 和 1）的不固定性組合，

zero and one,

so that no matter what the player does,

所以，不論玩家選擇什麼，

flip or no flip,

不論擲或不擲硬幣，這種 量子疊加態並不會改變。

the superposition remains intact.

It's kind of like stirring a mixture of two fluids.

這有點像是在攪拌兩種液體。

Whether or not you stir, the fluids remain in a mixture,

不論你攪或不攪， 兩種液體都混合在一起。

but in its final move,

但在它的最後一輪遊戲中，

the quantum computer can unmix the zero and one,

量子電腦能分離出 0 和 1，

perfectly recovering heads so that you lose every time.

將硬幣完美地恢復成正面朝上， 所以你每次都會輸。

(Laughter)

（笑聲）

If you think this is all a bit weird, you are absolutely right.

如果你覺得這一切十分怪異， 那你一點兒也沒錯。

Regular coins do not exist in combinations of heads and tails.

普通硬幣並不會以正面 和反面的組合形式存在。

We do not experience this fluid quantum reality

我們在日常生活中並不會經歷

這種不固定的、量子化的現實。

in our everyday lives.

So if you are confused by quantum,

所以，如果量子讓你困惑不解，

don't worry, you're getting it.

別擔心，你其實正在明白它。

(Laughter)

（笑聲）

But even though we don't experience quantum strangeness,

但是，雖然我們沒有 切身體驗量子的不可思議，

we can see its very real effects in action.

我們可以看到它產生了 非常真實的影響。

You've seen the data for yourself.

你們已經親眼看到資料了。

The quantum computer won

量子電腦會贏，

because it harnessed superposition and uncertainty,

是因為它利用量子疊加態和不確定性，

and these quantum properties are powerful,

這些量子特性非常強大，

not just to win coin games,

不僅能幫你贏得硬幣遊戲，

but also to build future quantum technologies.

也能用來建造未來的量子科技。

So let me give you three examples of potential applications

讓我舉三個例子， 說明那些有潛力的科技應用，

that could change our lives.

它們有可能改變我們的生活。

First of all, quantum uncertainty could be used to create private keys

首先，量子不確定性 可用于私鑰加密，

for encrypting messages sent from one location to another

將兩地之間傳輸的訊息進行加密，

so that hackers could not secretly copy the key perfectly,

因為量子不確定性，

駭客就無法偷偷地複製完整密鑰。

because of quantum uncertainty.

They would have to break the laws of quantum physics

他們若想盜用密鑰，

就得打破量子物理的法則。

to hack the key.

So this kind of unbreakable encryption is already being tested by banks

全世界的銀行和其他機構已經在測試

這種牢不可破的加密。

and other institutions worldwide.

Today, we use more than 17 billion connected devices globally.

現今，全球使用了超過 170 億個接入網路的裝置。

Just imagine the impact quantum encryption could have in the future.

想像一下，量子加密 在未來會有怎樣的影響。

Secondly, quantum technologies could also transform health care and medicine.

第二，量子科技也能轉變 醫療保健和醫學。

For example, the design and analysis of molecules for drug development

比如，在藥物開發中， 設計和分析各種分子

is a challenging problem today,

是現今很具挑戰性的問題，

and that's because exactly describing and calculating

這是因為，要精確地描述和計算

all of the quantum properties of all the atoms in the molecule

分子中所有原子的全部量子特性，

is a computationally difficult task, even for our supercomputers.

是非常難以計算的， 即使對於超級電腦也同樣。

But a quantum computer could do better,

但量子電腦能做得更好，

because it operates using the same quantum properties

因為它與它試圖模擬的分子一樣，

as the molecule it's trying to simulate.

使用了相同的量子特性來進行計算，

So future large-scale quantum simulations for drug development

因此，對於藥物開發， 未來的大規模量子模擬

could perhaps lead to treatments for diseases like Alzheimer's,

也許可以為阿茲海默症 之類的疾病找到治療方式，

which affects thousands of lives.

影響成千上萬的人。

And thirdly, my favorite quantum application

第三，是我最喜愛的量子應用，

is teleportation of information from one location to another

是將資訊從一個地點 即時傳遞到另一個地點，

without physically transmitting the information.

但不需要實際傳遞。

Sounds like sci-fi, but it is possible,

聽起來很科幻，但這是有可能的，

because these fluid identities of the quantum particles

因為量子粒子的這些不固定特質

can get entangled across space and time

在時間和空間中 可能會糾纏在一起，

in such a way that when you change something about one particle,

以至於當你改變了 其中的某一個粒子，

it can impact the other,

就會同時影響到其他粒子的狀態， 這就成了量子通信的「通道」。

and that creates a channel for teleportation.

It's already been demonstrated in research labs

在研究實驗室裡已經展示它可行，

and could be part of a future quantum internet.

可能會成為未來量子 網際網路的一部分。

We don't have such a network as yet,

我們目前尚無這樣的網路，

but my team is working on these possibilities,

但我的團隊正在努力實現它，

by simulating a quantum network on a quantum computer.

我們會在一台量子電腦上 模擬一個量子網路。

So we have designed and implemented some interesting new protocols

我們已經設計並實現了 一些有趣的、新的通訊協議，

such as teleportation among different users in the network

比如在網路上不同 用戶之間傳輸訊息，

and efficient data transmission

以及高效的文件傳輸，

and even secure voting.

甚至還有安全的選舉投票。

So it's a lot of fun for me, being a quantum physicist.

因此，我身為量子物理學家， 覺得這非常有意思。

I highly recommend it.

我極力推薦它。

(Laughter)

（笑聲）

We get to be explorers in a quantum wonderland.

我們有機會在量子仙境中當探險家。

Who knows what applications we will discover next.

誰知道接下來我們 會發現什麼新應用。

We must tread carefully and responsibly

當我們打造量子未來時，

我們必須要謹慎且可靠地向前邁進。

as we build our quantum future.

And for me, personally,

對我個人來說，

I don't see quantum physics as a tool just to build quantum computers.

我認為量子物理並不只是 用來打造量子電腦的工具。

I see quantum computers as a way for us to probe the mysteries of nature

我認為量子電腦能協助我們 探索大自然的謎題，

and reveal more about this hidden world outside of our experiences.

並更深入地揭示出我們 無法體驗的隱秘世界。

How amazing that we humans,

這是多麼不可思議，我們人類

with our relatively limited access to the universe,

對於宇宙的認識 和接觸是相對受限的，

can still see far beyond our horizons

我們卻單單靠著想像力和獨創性，

just using our imagination and our ingenuity.

仍然能觀察到遠遠 高於我們眼界的地方。

And the universe rewards us

而宇宙給我們的獎賞

by showing us how incredibly interesting and surprising it is.

就是讓我們看到它是 多麼有趣、讓人驚奇。

The future is fundamentally uncertain,

未來，本來就是不確定的，

and to me, that is certainly exciting.

但對我來說，我很確定， 它是讓人興奮的。

Thank you.

謝謝。

(Applause)

（掌聲）