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

薛定谔的猫：量子力学里的理想试验

翻译人员: LI HAO 校对人员: Qiwen Lu

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

奥地利物理学家埃尔·文薛定谔是量子力学的奠基人之一，

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

但是他最为大众所知的却是他从未做过的一项试验：

a thought experiment involving a cat.

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

一个关于猫的思想试验（即薛定谔的猫）

他假想将一只猫置于一个密闭盒子内，

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

里面安放了一个一小时内有50%几率杀死猫的装置。

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

在那一小时的结尾，他提出一个问题，现在猫是活的还是死的

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

常识告诉我们猫不是活的就是死的

but Schrödinger pointed out that according to quantum physics,

但是，薛定谔指出，根据量子物理

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

在打开盒子的前一瞬间，猫既是活的也是死的，即猫处于生与死的混合状态

同时

at the same time.

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

只有打开了盒子，我们才能知道猫是生还是死

除此之前，猫一直处于一种混沌可能性的状态，既生又死。

Until then, the cat is a blur of probability,

half one thing and half the other.

This seems absurd, which was Schrödinger's point.

薛定谔的观点听起来很荒谬

He found quantum physics so philosophically disturbing,

他发觉量子物理如此难以理解以至于他本人都放弃验证此理论并转而研究生物

that he abandoned the theory he had helped make

and turned to writing about biology.

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

虽然薛定谔的猫看上去很荒谬，但是，它却是很真实的，实际上，也是很基础的

In fact, it's essential.

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

如果量子物体不能同时处于双重状态，

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

我们现在用来观看此视频的电脑就不会存在

The quantum phenomenon of superposition

量子的叠加现象是自然物质波粒二象性作用的结果

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

In order for an object to have a wavelength,

一个物体要想有波长，就必须扩展空间范围

it must extend over some region of space,

which means it occupies many positions at the same time.

这就意味着它必须同时占据许多位置

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

限制在很小空间的不可能太明晰物体的波长

can't be perfectly defined, though.

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

所以它同时存在于波长内的许多不同地点

We don't see these wave properties for everyday objects

我们在日常生活的物品中看不到这些波

because the wavelength decreases as the momentum increases.

因为波长在变短的同时却有增长的趋势

And a cat is relatively big and heavy.

而因为猫相对而言比较大和重

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

如果我们取一个原子并放大到太阳系大小

the wavelength of a cat running from a physicist

那么猫奔向物理学家产生的波长就相当于太阳系里的一个小原子

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

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

它小到很难去探测，所以我们从未看到猫的波动

A tiny particle, like an electron, though,

但是，很小的物质，比如说一个电子却是能表明波粒二象性存在的证据

can show dramatic evidence of its dual nature.

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

如果我们一次把一个电子射向一个有两个狭窄裂缝的装置

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

远处的电子会像物质一样马上被探测出在哪个位置

like a particle.

But if you repeat this experiment many times,

我们大量重复此实验

keeping track of all the individual detections,

持续追踪所有电子的轨迹

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

你会发现它们的轨迹表现出了波的特征

a set of stripes - regions with many electrons

条纹区间内集聚了大量电子

separated by regions where there are none at all.

夹杂在没有电子的区间之中

Block one of the slits and the stripes go away.

遮挡住一个细微裂缝，条纹区间就不复存在

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

这表明电子的集聚形式是电子同时有两个裂缝可穿过的作用结果

at the same time.

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

一个电子无法选择通过哪个裂缝，但是，通过裂缝的电子却是同时发生的

but left and right simultaneously.

This superposition of states also leads to modern technology.

这种状态叠加也可由现代科学解释

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

饶原子核旋转的电子的轨道是分散的似波轨道

Bring two atoms close together,

使两个原子靠近，电子不需要选择原子轨道，只需要共享轨道

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

but are shared between them.

This is how some chemical bonds form.

这就是化学键的形式

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

分子中的电子不是在原子A或B中，是在A和B中

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

如果你添加更多的原子，电子会更加扩散，同时被大量原子共享

shared between vast numbers of atoms at the same time.

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

电子并不是牢固地绕某个原子旋转，

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

却在空间内绕着分子旋转

This gigantic superposition of states

这种庞大的状态叠加

determines the ways electrons move through the material,

表明了电子是如何在导体，绝缘体和半导体间运动的

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

Understanding how electrons are shared among atoms

了解电子被原子共享的方式

allows us to precisely control the properties of semiconductor materials,

使我们有可能精确地控制半导体材料的性能

like silicon.

比如说，硅

Combining different semiconductors in the right way

将不同的半导体以正确的方式组合

allows us to make transistors on a tiny scale,

令我们可以将晶体管制造成很小的规模

millions on a single computer chip.

集成大规模集成电路放在电脑芯片里

Those chips and their spread out electrons

这些芯片和扩散的电子掌控你们正在看此视频的电脑

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

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

有这么一个老笑话，互联网的存在使我们可以分享关于薛定谔的猫的视频

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

但是，溯本求源，互联网的出现却要归功于一位奥地利物理学家和那只虚构的猫

to an Austrian physicist and his imaginary cat.