I'm in the business of safeguarding secrets,

我的工作是保護秘密，

and this includes your secrets.

包括你們的秘密。

Cryptographers are the first line of defense

在一場已經激烈進行了 數世紀的戰爭中，

in an ongoing war that's been raging for centuries:

密碼專家是第一道防線：

a war between code makers

加密者和解密者之間的戰爭。

and code breakers.

這是一場資訊戰。

And this is a war on information.

現代，資訊的戰場是數位的。

The modern battlefield for information is digital.

戰場橫跨你的手機、

And it wages across your phones,

你的電腦，和網路。

your computers

我們的工作是要設計系統來將 你的電子郵件和信用卡卡號、

and the internet.

你的電話及文字訊息變成亂碼——

Our job is to create systems that scramble your emails and credit card numbers,

也包括那些限制級的自拍——

your phone calls and text messages --

（笑聲）

and that includes those saucy selfies --

我們要讓這些加密資訊

(Laughter)

只能夠被指定的接收者解開。

so that all of this information can only be descrambled

一直到最近之前，

by the recipient that it's intended for.

我們以為已經永久打贏了這場仗。

Now, until very recently,

目前，各位的智慧手機 所用的加密技術

we thought we'd won this war for good.

是我們認為無法破解， 且會一直無法破解的加密技術。

Right now, each of your smartphones is using encryption

我們錯了，

that we thought was unbreakable and that was going to remain that way.

因為量子電腦要出現了，

We were wrong,

它們會讓局勢完全改觀。

because quantum computers are coming,

在整個歷史上，密碼學和破解密碼 一直在玩貓捉老鼠的遊戲。

and they're going to change the game completely.

十六世紀時，

Throughout history, cryptography and code-breaking

蘇格蘭的瑪莉一世女王認為 她所發出的加密信件

has always been this game of cat and mouse.

只有她的士兵能夠解開。

Back in the 1500s,

但英格蘭的伊麗莎白 女王的解密者完全勝出。

Queen Mary of the Scots thought she was sending encrypted letters

他們破解了瑪莉的信件，

that only her soldiers could decipher.

發現她打算要刺殺伊麗莎白，

But Queen Elizabeth of England,

後來，他們便砍下了瑪莉一世的頭。

she had code breakers that were all over it.

幾世紀後，在二次大戰期間，

They decrypted Mary's letters,

納粹使用恩尼格瑪密碼來溝通，

saw that she was attempting to assassinate Elizabeth

他們認為這種更複雜的 加密方式是無法破解的。

and, subsequently, they chopped Mary's head off.

但，接著，好樣的艾倫圖靈，

A few centuries later, in World War II,

也就是發明了現代 電腦的那個傢伙，

the Nazis communicated using the Engima code,

他打造了一台機器 來破解恩尼格瑪密碼。

a much more complicated encryption scheme that they thought was unbreakable.

他破解了德國人的訊息，協助 阻止了希特勒和他的納粹德國。

But then good old Alan Turing,

所以，這個故事 已經進行了數個世紀。

the same guy who invented what we now call the modern computer,

密碼學家改進他們的加密方式，

he built a machine and used it to break Enigma.

接著，破解密碼的人又反擊， 找出方式來破解。

He deciphered the German messages

這場戰爭你來我往，競爭激烈。

and helped to bring Hitler and his Third Reich to a halt.

直到七○年代，

And so the story has gone throughout the centuries.

一些密碼學家有了重大的突破。

Cryptographers improve their encryption,

他們發現了一種 極強大的加密方式，

and then code breakers fight back and they find a way to break it.

叫做「公開金鑰密碼學」。

This war's gone back and forth, and it's been pretty neck and neck.

和過去使用過的所有方法不同，

That was until the 1970s,

打算交換機密資訊的雙方 不用事前交換秘密金鑰。

when some cryptographers made a huge breakthrough.

公開金鑰密碼學的美好之處就在於

They discovered an extremely powerful way to do encryption

它讓我們能夠和世界上 任何一個人進行安全的連結，

called "public-key cryptography."

不論我們以前是否交換過資料，

Unlike all of the prior methods used throughout history, it doesn't require

且它的速度超快，快到你我 都還沒意識到之前就已經完工。

that the two parties that want to send each other confidential information

不論是你傳訊息約好友出來喝酒，

have exchanged the secret key beforehand.

或者你是一間銀行， 要轉數十億美金給另一家銀行，

The magic of public-key cryptography is that it allows us to connect securely

現代加密方式讓我們能夠

with anyone in the world,

在幾毫秒的時間內 就完成安全的資料傳輸。

whether we've exchanged data before or not,

讓這種魔法成為可能的聰明想法

and to do it so fast that you and I don't even realize it's happening.

要仰賴困難的數學問題。

Whether you're texting your mate to catch up for a beer,

密碼學家對於計算機 做不到的事都深感興趣。

or you're a bank that's transferring billions of dollars to another bank,

比如，計算機可以 把任何兩個數字相乘，

modern encryption enables us to send data that can be secured

不論數字多大。

in a matter of milliseconds.

但換個方向——

The brilliant idea that makes this magic possible,

先從乘積開始，接著問：

it relies on hard mathematical problems.

「哪兩個數字相乘會得到 這個乘積？」——

Cryptographers are deeply interested in things that calculators can't do.

那就是困難的問題。

For example, calculators can multiply any two numbers you like,

若我請你找出哪兩個數字

no matter how big the size.

相乘會得到 851，

But going back the other way --

即使有計算機，

starting with the product and then asking,

這裡大部分的人也很難 在這場演說結束前解出答案。

"Which two numbers multiply to give this one?" --

如果我用大一點的數字，

that's actually a really hard problem.

地球上就沒有一台 計算機能找出答案來。

If I asked you to find which two-digit numbers multiply to give 851,

事實上，就連世界上 最快的超級電腦，

even with a calculator,

也要花上比宇宙生命更長的時間

most people in this room would have a hard time finding the answer

才找得出是哪兩個數字 相乘得到這個乘積。

by the time I'm finished with this talk.

這個問題叫做 「整數的因數分解」，

And if I make the numbers a little larger,

各位現在的智慧手機和筆電

then there's no calculator on earth that can do this.

就是使用這個方法 來確保資料的安全性。

In fact, even the world's fastest supercomputer

它是現代加密技術的基礎。

would take longer than the life age of the universe

既然地球上所有的計算能力 結合起來都無法破解它，

to find the two numbers that multiply to give this one.

因此我們密碼學家便認為 我們已經找到方法

And this problem, called "integer factorization,"

可以永遠領先破解密碼者了。

is exactly what each of your smartphones and laptops is using right now

也許我們太驕傲了，

to keep your data secure.

因為就在我們自以為 已經打了勝仗時，

This is the basis of modern encryption.

一群二十世紀的 物理學家加入戰局，

And the fact that all the computing power on the planet combined can't solve it,

他們點出，宇宙的定律，

that's the reason we cryptographers thought we'd found a way

也就是做為現代密碼學 基礎的那些定律，

to stay ahead of the code breakers for good.

它們並非我們所想的那樣。

Perhaps we got a little cocky

我們認為一個物體不可能 同時出現在兩個地方。

because just when we thought the war was won,

並非如此。

a bunch of 20th-century physicists came to the party,

我們以為沒有任何東西能夠

and they revealed that the laws of the universe,

同時順時鐘又逆時鐘轉動。

the same laws that modern cryptography was built upon,

但那並不正確。

they aren't as we thought they were.

我們以為在宇宙 相對兩邊的兩個物體，

We thought that one object couldn't be in two places at the same time.

相距數光年之遠，

It's not the case.

它們就不可能即時影響彼此。

We thought nothing can possibly spin clockwise and anticlockwise

我們又錯了。

simultaneously.

人生似乎總是這樣，不是嗎？

But that's incorrect.

就在你以為你什麼 都考慮了也準備好了，

And we thought that two objects on opposite sides of the universe,

卻出現一票物理學家， 點出宇宙的基本定律

light years away from each other,

和你所想的完全不一樣？

they can't possibly influence one another instantaneously.

這把一切都搞砸了。

We were wrong again.

（笑聲）

And isn't that always the way life seems to go?

在非常微小的次原子領域中，

Just when you think you've got everything covered, your ducks in a row,

在電子和光子的層級上，

a bunch of physicists come along

我們知道且喜愛的物理標準定律，

and reveal that the fundamental laws of the universe are completely different

都可以丟掉了。

to what you thought?

這就要談到量子力學的定律了。

(Laughter)

在量子力學中，

And it screws everything up.

電子可以同時順時鐘 和逆時鐘轉動，

See, in the teeny tiny subatomic realm,

光子可以同時位在兩個地方。

at the level of electrons and protons,

聽起來很科幻，

the classical laws of physics,

但那只是因為我們的宇宙 有著很瘋狂的量子特性，

the ones that we all know and love,

這特性隱藏著沒被我們發現。

they go out the window.

一直藏到二十世紀才被我們發現。

And it's here that the laws of quantum mechanics kick in.

但現在我們知道了， 全世界都加入軍備競賽，

In quantum mechanics,

比賽建造量子電腦——

an electron can be spinning clockwise and anticlockwise at the same time,

量子電腦可以利用 這種怪異量子行為的力量。

and a proton can be in two places at once.

這種電腦非常具有革命性

It sounds like science fiction,

且非常強大，

but that's only because the crazy quantum nature of our universe,

厲害到會讓現今最快的超級電腦

it hides itself from us.

相較之下都變得很沒用。

And it stayed hidden from us until the 20th century.

事實上，針對我們 很感興趣的某些問題，

But now that we've seen it, the whole world is in an arms race

現今最快的超級電腦還比較 接近算盤，而非量子電腦。

to try to build a quantum computer --

是的，算盤就是那些 有珠子在上頭的木製品。

a computer that can harness the power of this weird and wacky quantum behavior.

量子電腦能模擬化學和生物過程，

These things are so revolutionary

遠超過我們的標準電腦 能做到的程度。

and so powerful

因此，量子電腦保證 能協助我們解決

that they'll make today's fastest supercomputer

地球上一些最大的問題。

look useless in comparison.

它們可以協助我們對抗全球飢荒，

In fact, for certain problems that are of great interest to us,

處理氣候變遷，

today's fastest supercomputer is closer to an abacus

針對我們目前沒輒的 疾病和流行病找出解藥，

than to a quantum computer.

創造出超人類的人工智慧，

That's right, I'm talking about those little wooden things with the beads.

還有，可能比上述這些都更重要的是

Quantum computers can simulate chemical and biological processes

能協助我們了解宇宙的本質。

that are far beyond the reach of our classical computers.

但，這麼驚人的潛能

And as such, they promise to help us solve some of our planet's biggest problems.

也伴隨著極大的風險。

They're going to help us combat global hunger;

還記得我先前談到的那些大數字嗎？

to tackle climate change;

我指的不是 851。

to find cures for diseases and pandemics for which we've so far been unsuccessful;

事實上，如果在座有人分心 去試著找出那些因數，

to create superhuman artificial intelligence;

我來幫你從痛苦中解脫， 答案是 23 乘以 37。

and perhaps even more important than all of those things,

（笑聲）

they're going to help us understand the very nature of our universe.

我指的是在 857 之後 更大更大的那個數字。

But with this incredible potential

雖然現今最快的超級電腦 花上宇宙一生的時間

comes an incredible risk.

也無法找出那些因數，

Remember those big numbers I talked about earlier?

但量子電腦能夠將 比那個數字更大許多的數字

I'm not talking about 851.

輕易拆解成因數。

In fact, if anyone in here has been distracted

量子電腦能破解目前用來保護你我

trying to find those factors,

抵禦駭客的所有加密技術。

I'm going to put you out of your misery and tell you that it's 23 times 37.

且輕輕鬆鬆就能辦到。

(Laughter)

讓我這麼說：

I'm talking about the much bigger number that followed it.

如果量子計算是一支長矛，

While today's fastest supercomputer couldn't find those factors

那現代的加密系統，

in the life age of the universe,

也就是數十年都沒被破解， 一直在保護我們的系統，

a quantum computer could easily factorize numbers

它就像是用衛生紙做的盾牌。

way, way bigger than that one.

任何人只要能夠使用量子電腦， 就等於拿到一把萬能鑰匙，

Quantum computers will break all of the encryption currently used

在數位世界，他們想要 解鎖什麼就能解鎖什麼。

to protect you and I from hackers.

他們能從銀行偷錢，

And they'll do it easily.

控制經濟，

Let me put it this way:

能讓醫院斷電或者發射核彈，

if quantum computing was a spear,

還可以只是坐著，透過網路攝影機

then modern encryption,

監視我們，不會被我們知道。

the same unbreakable system that's protected us for decades,

在我們現在所使用的電腦上，

it would be like a shield made of tissue paper.

像這台電腦上，資訊的基礎單位

Anyone with access to a quantum computer will have the master key

叫做「位元」。

to unlock anything they like in our digital world.

單一個位元可能有兩種狀態：

They could steal money from banks

它可能是零或一。

and control economies.

我媽在世界的另一端， 當我和她視訊通話時，

They could power off hospitals or launch nukes.

她看到這張投影片一定會殺了我——

Or they could just sit back and watch all of us on our webcams

（笑聲）

without any of us knowing that this is happening.

我們其實只是發送一串 又一串的零和一給彼此，

Now, the fundamental unit of information on all of the computers we're used to,

它們會在電腦及衛星間彈來彈去，

like this one,

快速傳輸我們的資料。

it's called a "bit."

位元非常有用，無庸置疑。

A single bit can be one of two states:

事實上，我們目前 用科技所做的任何事，

it can be a zero or it can be a one.

都受惠於這些好用的位元。

When I FaceTime my mum from the other side of the world --

但，我們開始了解到位元很不擅長

and she's going to kill me for having this slide --

模擬複雜的分子和粒子。

(Laughter)

原因是因為，在某種意義上，

we're actually just sending each other long sequences of zeroes and ones

次原子過程可以同時進行 兩件以上相反的事情，

that bounce from computer to computer, from satellite to satellite,

因為它們遵循的是 這些怪異的量子力學規則。

transmitting our data at a rapid pace.

所以，上個世紀末，

Bits are certainly very useful.

一些非常聰明的物理學家 想出了一個天才點子：

In fact, anything we currently do with technology

改用量子力學的原則來建造電腦。

is indebted to the usefulness of bits.

在量子電腦上，資訊的基礎單位

But we're starting to realize

叫做「量子位」。

that bits are really poor at simulating complex molecules and particles.

是「量子位元」的簡稱。

And this is because, in some sense,

量子位不只有零和一兩個狀態，

subatomic processes can be doing two or more opposing things

它可以有無限多個狀態。

at the same time

因為它可以同時是零和一的組合，

as they follow these bizarre rules of quantum mechanics.

這種現象被我們稱為「疊加」。

So, late last century,

當有兩個量子位疊加時，

some really brainy physicists had this ingenious idea:

我們其實是在處理全部四種組合：

to instead build computers that are founded

零和零、零和一、 一和零、一和一。

on the principles of quantum mechanics.

有三個量子位時，

Now, the fundamental unit of information of a quantum computer,

我們就有八種組合的疊加，

it's called a "qubit."

以此類推。

It stands for "quantum bit."

每當我們增加一個量子位，

Instead of having just two states, like zero or one,

我們同時能用的

a qubit can be an infinite number of states.

疊加組合數目就會加倍。

And this corresponds to it being some combination of both zero and one

所以，當我們擴大規模， 使用許多量子位時，

at the same time,

我們同時能夠用的組合數目

a phenomenon that we call "superposition."

會是指數增加。

And when we have two qubits in superposition,

從這點就可以略知 量子電腦的能力從何而來。

we're actually working across all four combinations

在現代的加密技術中，

of zero-zero, zero-one, one-zero and one-one.

我們的秘密金鑰，比如 那個大數字的兩個因數，

With three qubits,

它們都是長串的零和一。

we're working in superposition across eight combinations,

要找出它們，標準的電腦

and so on.

必須把所有可能組合 一組一組試過，

Each time we add a single qubit, we double the number of combinations

直到找到行得通的組合， 就破解了我們的加密。

that we can work with in superposition

但在量子電腦上，

at the same time.

只要有足夠的疊加量子位，

And so when we scale up to work with many qubits,

就可以同時從 所有組合來擷取資訊。

we can work with an exponential number of combinations

只要少數幾個步驟，

at the same time.

量子電腦就能把所有 不正確的組合排除，

And this just hints at where the power of quantum computing is coming from.

鎖定正確的組合，

Now, in modern encryption,

接著揭露我們寶貴的秘密。

our secret keys, like the two factors of that larger number,

在瘋狂的量子層級上，

they're just long sequences of zeroes and ones.

發生的現象非常不可思議。

To find them,

許多頂尖物理學家 所擁有的傳統知識是——

a classical computer must go through every single combination,

你們要專心聽我說，別分神——

one after the other,

每種組合其實是 在它自己的平行宇宙中，

until it finds the one that works and breaks our encryption.

由它自己的量子電腦來檢查。

But on a quantum computer,

每個組合加在一起， 就像一池水中的水波。

with enough qubits in superposition,

錯誤的組合

information can be extracted from all combinations at the same time.

會彼此抵消。

In very few steps,

正確的組合

a quantum computer can brush aside all of the incorrect combinations,

會強化、放大彼此。

home in on the correct one

所以，在量子計算程式結束時，

and then unlock our treasured secrets.

留下來的就只有正確答案，

Now, at the crazy quantum level,

我們在這個宇宙中 就可以觀察到這個答案。

something truly incredible is happening here.

如果你覺得還無法 完全理解，別擔心。

The conventional wisdom held by many leading physicists --

（笑聲）

and you've got to stay with me on this one --

你不孤單。