Schrödinger's cat: A thought experiment in quantum mechanics - Chad Orzel

薛丁格的貓：一個量子力學的思想實驗 - Chad Orzel

譯者: Sherry Chen 審譯者: 瑞文Eleven 林Lim

奧地利物理學家薛丁格 是量子力學的創始人之一，

Austrian physicist Erwin Schrödinger is one of the founders of quantum mechanics,

but he's most famous for something he never actually did:

但最讓他出名的 其實是一件他從沒做過的事情：

a thought experiment involving a cat.

一個關於貓的思想實驗。

He imagined taking a cat and placing it in a sealed box

他想像將一隻貓 放進一個密封的盒子中，

with a device that had a 50% chance of killing the cat in the next hour.

接下來的一小時內， 貓有50％的機率會被盒中的儀器殺死。

At the end of that hour, he asked, "What is the state of the cat?"

一小時過去後，他問道： "這隻貓現在是何種狀態呢？"

Common sense suggests that the cat is either alive or dead,

常識告訴我們， 這隻貓要麼活著，要麼死了。

but Schrödinger pointed out that according to quantum physics,

但是薛丁格指出，根據量子力學，

at the instant before the box is opened, the cat is equal parts alive and dead,

在盒子打開的那一刻之前，

這隻貓在同一時刻，既是死的也是活的；

at the same time.

It's only when the box is opened that we see a single definite state.

只有在盒子被打開的那一刻， 我們才能看見單一固定的狀態。

Until then, the cat is a blur of probability,

在那之前，貓的生死純粹是 模糊的概率問題。

half one thing and half the other.

一半是死、一半是活。

This seems absurd, which was Schrödinger's point.

這似乎很荒謬， 但這正是薛丁格想要指出的。

He found quantum physics so philosophically disturbing,

他發現量子力學 在哲學上是如此令人煩惱，

that he abandoned the theory he had helped make

以至於讓他徹底放棄了這個 他幫助建立起來的理論，

and turned to writing about biology.

轉而投向生物學的研習。

As absurd as it may seem, though, Schrödinger's cat is very real.

儘管這個實驗聽上去很荒謬， 但薛丁格的貓卻十分真實。

In fact, it's essential.

實際上，它甚為關鍵。

If it weren't possible for quantum objects to be in two states at once,

如果量子物體不能夠 以兩種狀態同時存在的話，

the computer you're using to watch this couldn't exist.

那你用來看這段影片的電腦 也就不會存在了。

The quantum phenomenon of superposition

疊加的量子現象

is a consequence of the dual particle and wave nature of everything.

是一切物質波粒二象性的結果，

In order for an object to have a wavelength,

一個物體要有波長，

it must extend over some region of space,

就必須擴展空間範圍，

which means it occupies many positions at the same time.

這就意味著它必須 同時佔據許多位置。

The wavelength of an object limited to a small region of space

物質的波長限制在很小的空間中，

can't be perfectly defined, though.

不能明確定位，

So it exists in many different wavelengths at the same time.

所以它同時存在於許多不同的波長中。

We don't see these wave properties for everyday objects

我們在日常事物中無法看到這些波，

because the wavelength decreases as the momentum increases.

因為波長會隨著動量的增加而遞減。

And a cat is relatively big and heavy.

而貓的體積相對較大、質量也較重，

If we took a single atom and blew it up to the size of the Solar System,

如果我們將一個原子放大到太陽系大小，

the wavelength of a cat running from a physicist

那麼貓奔向物理學家時產生的波長，

would be as small as an atom within that Solar System.

才相當於太陽系裡的原子般大小。

That's far too small to detect, so we'll never see wave behavior from a cat.

因小到難以探測，所以 我們從未看到貓的波動性。

A tiny particle, like an electron, though,

然而，例如電子般的粒子，

can show dramatic evidence of its dual nature.

卻是證明波粒二象性存在的證據。

If we shoot electrons one at a time at a set of two narrow slits cut in a barrier,

如果我們把一個電子射向雙狹縫裝置，

each electron on the far side is detected at a single place at a specific instant,

電子另一側的位置馬上會被探測到，

like a particle.

就像粒子一樣。

But if you repeat this experiment many times,

但如果我們大量重複此實驗，

keeping track of all the individual detections,

將每個檢測結果記錄下來，

you'll see them trace out a pattern that's characteristic of wave behavior:

你會發現它們的軌跡表現出波的特徵，

a set of stripes - regions with many electrons

條紋區間內集聚了大量電子，

separated by regions where there are none at all.

夾雜在沒有電子的區間之中。

Block one of the slits and the stripes go away.

一旦遮擋住一個狹縫， 條紋區間隨之消失，

This shows that the pattern is a result of each electron going through both slits

顯示電子的集聚形態因為同一時刻

有兩個狹縫可供穿過的作用結果。

at the same time.

A single electron isn't choosing to go left or right

單個電子無法選擇通過哪個狹縫，

but left and right simultaneously.

但是，電子束卻是同時通過兩個狹縫。

This superposition of states also leads to modern technology.

此種疊加狀態也使許多現代科技成真。

An electron near the nucleus of an atom exists in a spread out, wave-like orbit.

繞原子核旋轉的電子 存在於延伸出的似波軌道中，

Bring two atoms close together,

當兩個原子相互靠近時，

and the electrons don't need to choose just one atom

電子不需要選擇原子軌道，

but are shared between them.

只需要共用軌道，

This is how some chemical bonds form.

這就是一些化學鍵的形成方式。

An electron in a molecule isn't on just atom A or atom B, but A+ B.

一個分子中的電子並不是純粹 A原子或B原子所擁有，而是兩者共有。

As you add more atoms, the electrons spread out more,

如果你加入更多原子， 電子們就會分布得更加分散，

shared between vast numbers of atoms at the same time.

同時被許多個原子所共用，

The electrons in a solid aren't bound to a particular atom

固體中的電子並非固定在某個原子上，

but shared among all of them, extending over a large range of space.

而是在一個較大空間中延展開， 被不同的原子所共用。

This gigantic superposition of states

這種巨大的疊加狀態，

determines the ways electrons move through the material,

決定了原子構成物質的形式，

whether it's a conductor or an insulator or a semiconductor.

可能是導體、絕緣體或半導體。

Understanding how electrons are shared among atoms

理解電子是如何被原子所共用，

allows us to precisely control the properties of semiconductor materials,

能夠讓我們得以精確控制半導體的性質，

like silicon.

例如矽半導體。

Combining different semiconductors in the right way

將不同的半導體以正確的形式合成，

allows us to make transistors on a tiny scale,

使讓我們製造作出極小的電晶體，

millions on a single computer chip.

在一小片電腦晶片上 就有上百萬個電晶體。

Those chips and their spread out electrons

而那些晶片，以及其中流動的電子，

power the computer you're using to watch this video.

使你用來觀看此短片的電腦得以運作。

An old joke says that the Internet exists to allow the sharing of cat videos.

有個老套的笑話： 因網路的存在， 讓人們得以分享貓咪影片。

At a very deep level, though, the Internet owes its existance

然而從一個很深刻的層次來說： 網路的存在，

to an Austrian physicist and his imaginary cat.

恰恰是源於一個奧地利物理學家 和他想像出來的貓。