A beginner's guide to quantum computing | Shohini Ghose

翻译人员: Wanna Shi 校对人员: Lipeng Chen

Let's play a game.

我们来玩个游戏。

Imagine that you are in Las Vegas,

假设你现在

在拉斯维加斯的一个赌场里，

in a casino,

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

而且你决定要在赌场内的 某台电脑上玩游戏，

just like you might play solitaire or chess.

你可能会玩纸牌或者象棋。

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

电脑能像真人玩家一样， 在游戏中出牌或走棋。

This is a coin game.

这是一个硬币游戏。

It starts with a coin showing heads,

首先，一个硬币正面朝上，

and the computer will play first.

电脑会先开始玩。

It can choose to flip the coin or not,

电脑可以选择 把硬币翻过来或者不翻，

but you don't get to see the outcome.

但是你看不到结果。

Next, it's your turn.

接下来就轮到你了。

You can also choose to flip the coin or not,

你也可以选择 把硬币翻过来或者不翻，

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

而你的选择不会 被透露给你的对手（电脑）。

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

接下来，又轮到电脑做选择： 把硬币翻过来或者不翻。

and after these three rounds,

三轮过后，

the coin is revealed,

硬币的朝向会被揭晓。

and if it is heads, the computer wins,

如果正面朝上，那电脑就赢了；

if it's tails, you win.

如果反面朝上，那你就赢了。

So it's a pretty simple game,

这是一个非常简单的游戏，

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

如果每个人都老实参与游戏， 而且硬币也是质地均匀的，

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

那你赢得这场游戏的概率是50%。

And to confirm that,

为了确认这一点，

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

我让我的学生在我们的 电脑上玩了这个游戏。

and after many, many tries,

尝试了很多很多次之后，

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

他们的获胜率恰巧为50% 或者接近50%，

as expected.

意料之中。

Sounds like a boring game, right?

这个游戏听起来有些无聊，是吧？

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

但是，如果你能在量子计算机上 玩这个游戏，那会怎样呢？

Now, Las Vegas casinos do not have quantum computers,

目前，据我所知，

拉斯维加斯的赌场并没有量子计算机，

as far as I know,

but IBM has built a working quantum computer.

不过IBM已经制造了一台 可以正常运行的量子计算机。

Here it is.

就是这台。

But what is a quantum computer?

什么是量子计算机呢？

Well, quantum physics describes

量子力学研究

the behavior of atoms and fundamental particles,

原子和基本粒子，如电子、光子的

like electrons and photons.

运动规律。

So a quantum computer operates

量子计算机通过 控制这些粒子的运动

by controlling the behavior of these particles,

来实现运行，

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

但其运行方式 与普通电脑截然不同。

So a quantum computer is not just a more powerful version

量子计算机可不只是

of our current computers,

现有电脑的加强版，

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

就像电灯泡不是 蜡烛的加强版一样。

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

即使你不断地改良蜡烛， 也做不出电灯泡。

电灯泡需要完全不同的技术，

A light bulb is a different technology,

based on deeper scientific understanding.

基于更深层次的科学认识。

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

同样，量子计算机是 一种基于量子力学的

based on the science of quantum physics,

全新设备；

and just like a light bulb transformed society,

就像电灯泡带来了社会变革，

quantum computers have the potential to impact

量子计算机也很可能

so many aspects of our lives,

会影响人类生活的方方面面，

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

如安全需求、卫生保健、 甚至是互联网。

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

因此，全球数家公司 正在研发量子计算机，

量子计算机究竟为何 让我们如此激动？

and to see what the excitement is all about,

let's play our game on a quantum computer.

我们在量子计算机上玩个游戏看看。

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

我可以就地登入 IBM的量子计算机，

which means I can play the game remotely,

也就是说， 我可以远程玩游戏，

and so can you.

你也可以。

首先，要记得提前 从TED获得一个邮箱，

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

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

你参与游戏的话，

邮箱信息会问你是否要翻转硬币。

if you played the game.

实际上，我们会问你 要选圆圈还是方块。

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

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

你事先并不知道， 不过你选圆圈就是要把硬币翻面，

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

你选方块就是不翻面。

We received 372 responses.

我们收到了372条回复。

Thank you.

在此要谢谢大家的参与。

That means we can play 372 games against the quantum computer

这意味着我们可以用你们的选择

跟量子计算机玩372把游戏。

using your choices.

And it's a pretty fast game to play,

这个游戏很快就能结束，

so I can show you the results right here.

我现在就可以给你们看结果。

Unfortunately, you didn't do very well.

不幸的是，你们运气不太好。

(Laughter)

（笑声）

The quantum computer won almost every game.

量子计算机在每轮游戏中基本都会赢。

只输了几把，而这是计算机 自身的操作错误造成的。

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

(Laughter)

（笑声）

So how did it achieve this amazing winning streak?

那么，量子计算机怎么能够 如此惊人的接连获胜呢？

It seems like magic or cheating,

看起来像是魔术或作弊一样，

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

但实际上，这是因为 量子力学在发挥作用。

Here's how it works.

操作如下：

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

普通计算机用比特 模仿硬币的正面或反面，

a zero or a one,

即0或者1，

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

或是用电脑芯片内的 电流供断来模仿。

A quantum computer is completely different.

量子计算机则全然不同。

量子比特更易变， 具有非二进制特性，

A quantum bit has a more fluid, nonbinary identity.

能以0和1叠加， 或者说组合的形式存在，

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

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

有可能为0， 有可能为1。

In other words, its identity is on a spectrum.

换句话说， 其特性处于一个范围内。

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

比如说，它有70%的可能性是0，

and a 30 percent chance of being one

和30%的可能性是1，

or 80-20 or 60-40.

也可能是八二分或六四分，，

有无穷的可能性。

The possibilities are endless.

The key idea here

关键是

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

我们需要放弃绝对的0和1，

and allow for some uncertainty.

接受一些不确定性。

So during the game,

所以在玩游戏时，

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

量子计算机创造了正面和反面，

即0和1的易变组合。

zero and one,

so that no matter what the player does,

所以不论玩家怎么选，

flip or no flip,

将硬币翻面与否，

the superposition remains intact.

叠加均不受影响。

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

就像是搅拌两种液体的混合物。

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

不论你搅拌与否， 两种液体仍在混合物中，

but in its final move,

但是在最后一步，

the quantum computer can unmix the zero and one,

量子计算机可以把混合的0和1分开，

perfectly recovering heads so that you lose every time.

让硬币正面朝上， 所以你每次都赢不了。

(Laughter)

（笑声）

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

如果你觉得这很奇怪，那就对了。

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

普通硬币并没有 两面同时朝上这种状态。

我们在日常生活中也 从未经历过这种不确定的

We do not experience this fluid quantum reality

in our everyday lives.

量子实际状态。

So if you are confused by quantum,

所以如果你对量子感到困惑，

don't worry, you're getting it.

不用担心，你终究会明白的。

(Laughter)

（笑声）

But even though we don't experience quantum strangeness,

不过即便我们没有 见识过量子的奇特之处，

we can see its very real effects in action.

我们还是能看到 其实实在在的影响。

You've seen the data for yourself.

你们也亲眼看到游戏结果了。

The quantum computer won

量子计算机赢了，

because it harnessed superposition and uncertainty,

因为量子计算机利用了 叠加和不确定性，

and these quantum properties are powerful,

而这些量子特性非常强大。

not just to win coin games,

不仅仅能在硬币游戏中获胜，

but also to build future quantum technologies.

也能创造未来的量子技术。

So let me give you three examples of potential applications

量子技术的潜在应用 能够改变我们的生活，

that could change our lives.

我来举三个例子。

首先，量子不确定性 可以用来创造私钥，

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

for encrypting messages sent from one location to another

将从一个地方发到 另一个地方的信息加密，

so that hackers could not secretly copy the key perfectly,

这样黑客就不能偷偷 完全复制这个私钥了，

because of quantum uncertainty.

就是因为量子具有不确定性。

They would have to break the laws of quantum physics

要想获得私钥，黑客得先打破

to hack the key.

量子力学法则。

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

目前全球银行和其他机构已经在测试

这种无法破解的加密方法了。

and other institutions worldwide.

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

当前，全球的联网设备多达170亿台。

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

大家可以试想一下量子加密 在未来的影响力会有多大。

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

其次，量子技术也能改变 医疗保健和医药行业。

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

比如，在药物研发过程中 设计和分析分子

is a challenging problem today,

迄今仍是一个极具挑战的难题，

and that's because exactly describing and calculating

因为要准确描述和计算

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

分子中所有原子的 所有量子特性，

is a computationally difficult task, even for our supercomputers.

从计算角度而言是一个极难的任务， 对于我们的超级计算机而言也不例外。

But a quantum computer could do better,

但是量子计算机更胜一筹，

because it operates using the same quantum properties

因为量子计算机运行时

as the molecule it's trying to simulate.

运用了与其试图模拟的分子 相同的量子特性。

So future large-scale quantum simulations for drug development

所以在未来的药物研发中， 大规模量子模拟

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

或许有助于治疗 影响成千上万人的疾病，

which affects thousands of lives.

如阿尔兹海默症。

And thirdly, my favorite quantum application

第三，我个人最喜欢的量子应用是

is teleportation of information from one location to another

量子瞬移，即将信息 从一个地点传送到另一个地点，

而不需要实际的传播途径。

without physically transmitting the information.

Sounds like sci-fi, but it is possible,

听起来就像科幻小说， 但这是可能实现的，

because these fluid identities of the quantum particles

因为这些量子粒子的易变特性

can get entangled across space and time

能跨越时空发生纠缠，

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

这样你更改一个粒子的某些东西时，

it can impact the other,

也会影响另一个粒子，

and that creates a channel for teleportation.

这就创造出了量子瞬移通道。

It's already been demonstrated in research labs

研究实验室已经就此进行了证实，

and could be part of a future quantum internet.

这将构成未来量子网络的一部分。

We don't have such a network as yet,

我们现在还没有这样的网络，

but my team is working on these possibilities,

不过我的团队正在 为了这些可能性而努力，

by simulating a quantum network on a quantum computer.

在量子计算机上模拟量子网络。

我们设计实施了 一些有趣的新网络协议，

So we have designed and implemented some interesting new protocols

such as teleportation among different users in the network

如不同网络用户间的量子瞬移

and efficient data transmission

和高效数据传输，

甚至还包括安全投票。

and even secure voting.

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

当一名量子物理学家， 我觉得很好玩，

I highly recommend it.

也极力推荐大家跟随我的脚步。

(Laughter)

（笑声）

We get to be explorers in a quantum wonderland.

让我们一同探索神奇的量子世界。

Who knows what applications we will discover next.

谁知道接下来我们又会 发现什么样的应用呢？

We must tread carefully and responsibly

打造量子未来时，

as we build our quantum future.

我们务必要谨慎负责。

And for me, personally,

就我个人而言，

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

我并不只把量子力学 当做是制造量子计算机的工具，

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

而是将使用量子计算机 视作探索自然奥秘、

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

揭示未知世界的方法。

How amazing that we humans,

人类是多么的伟大，

with our relatively limited access to the universe,

虽然我们了解浩瀚宇宙的渠道有限，

can still see far beyond our horizons

但是凭我们的想象力与创造力，

just using our imagination and our ingenuity.

我们能够不断拓宽视野。

And the universe rewards us

而浩瀚的宇宙会也会回报我们，

by showing us how incredibly interesting and surprising it is.

向我们展示它有趣又惊艳的一面。

从根本上来说，未来具有不确定性；

The future is fundamentally uncertain,

and to me, that is certainly exciting.

对我来说，这着实激动人心。

Thank you.

谢谢大家。

(Applause)

（掌声）