What in the world is topological quantum matter? - Fan Zhang

翻译人员: Chong Liu 校对人员: Alicia Cai

What if electricity could travel forever without being diminished?

如果电流可以一直毫无损耗地 流动会怎么样呢？

What if a computer could run exponentially faster with perfect accuracy?

如果电脑的运行速度可以指数增长 并保持准确无误会怎么样呢？

What technology could those abilities build?

什么样的科技才能使上述想象成真呢？

We may be able to find out thanks to the work of the three scientists

也许我们可以找出一个方法， 为此我们要感谢

who won the Nobel Prize in Physics in 2016.

获得2016年诺贝尔奖的三位科学家，

David Thouless,

David Thouless，

Duncan Haldane,

Duncan Haldane 和 Michael Kosterlitz，

and Michael Kosterlitz won the award for discovering

他们三位发现

that even microscopic matter at the smallest scale

即使是最小尺度的微观物质

can exhibit macroscopic properties and phases that are topological.

也可以展现拓扑 的宏观性质和各种相态。

But what does that mean?

但这是什么意思呢？

First of all, topology is a branch of mathematics

首先，拓扑学是数学的一个分支，

that focuses on fundamental properties of objects.

它关注物体的基本属性。

Topological properties don't change when an object is gradually stretched or bent.

当物体逐渐伸展或弯曲时， 它的拓扑性质不会改变。

The object has to be torn or attached in new places.

物体必须被撕裂或附着在新的地方。

A donut and a coffee cup look the same to a topologist

在拓扑学家看来，一个甜甜圈 和一只咖啡杯是毫无差别的，

because they both have one hole.

因为它们都有一个洞。

You could reshape a donut into a coffee cup

你可以把一个甜甜圈 重塑为一只咖啡杯，

and it would still have just one.

它仍旧只会有一个洞。

That topological property is stable.

这种拓扑学属性是稳定的。

On the other hand, a pretzel has three holes.

从另一个方面讲， 一个蝴蝶脆饼有三个洞。

There are no smooth incremental changes that will turn a donut into a pretzel.

没有平稳的、不断增加的改变可以 使一个甜甜圈变成一个蝴蝶脆饼。

You'd have to tear two new holes.

你必须撕出两个新口子才行。

For a long time, it wasn't clear whether topology was useful

在很长一段时间里， 人们并不清楚拓扑学能否用于

for describing the behaviors of subatomic particles.

描述亚原子粒子的行为。

That's because particles, like electrons and photons,

这是因为粒子，比如电子和光子

are subject to the strange laws of quantum physics,

遵循奇怪的量子物理法则，

which involve a great deal of uncertainty

其中包含了很多不确定的因素，

that we don't see at the scale of coffee cups.

在咖啡杯的层面我们根本观察不到。

But the Nobel Laureates discovered that topological properties

但这三位诺贝尔奖得主发现，

do exist at the quantum level.

拓扑学的属性是存在于 量子水平上的。

And that discovery may revolutionize materials science,

这个发现也许可以 在材料科学，电子工程学

electronic engineering,

还有计算机科学中

and computer science.

引发革命。

That's because these properties lend surprising stability

这是因为这些属性 在微妙的量子世界里

and remarkable characteristics to some exotic phases of matter

为物质的一些奇异相态

in the delicate quantum world.

提供了惊人的稳定性 和显著的特征。

One example is called a topological insulator.

举一个“拓扑绝缘体”的例子。

Imagine a film of electrons.

想像一个电子薄膜。

If a strong enough magnetic field passes through them,

如果有一个足够强 的电磁场从中穿过，

each electron will start traveling in a circle,

每一个电子就会开始 进行圆周性的运动，

which is called a closed orbit.

这一轨迹叫做近轨。

Because the electrons are stuck in these loops,

因为这些电子都被困在这些环里，

they're not conducting electricity.

它们没有办法产生电。

But at the edge of the material,

但在材料的边缘，

the orbits become open, connected, and they all point in the same direction.

这些轨道变得开放、互联， 并且有着相同的指向。

So electrons can jump from one orbit to the next

这时，电子就可以 从一个环跳到下一个环上，

and travel all the way around the edge.

在这块材料的边缘移动。

This means that the material conducts electricity around the edge

这就意味着电子只能 在材料的边缘导电，

but not in the middle.

而不能在材料的中间部分导电。

Here's where topology comes in.

在这里，拓扑学可以发挥作用了。

This conductivity isn't affected by small changes in the material,

这块材料的传导性并没有 被材料中细小的变化所影响，

like impurities or imperfections.

比如杂质，或者缺陷。

That's just like how the hole in the coffee cup

它们就像咖啡杯的那个洞一样，

isn't changed by stretching it out.

不会因为形变而产生变化。

The edge of such a topological insulator has perfect electron transport:

在这样一块拓扑绝缘体的边缘 产生了完美的电子运动，

no electrons travel backward,

没有电子回流，

no energy is lost as heat,

没有能量以热量的形式损耗，

and the number of conducting pathways can even be controlled.

就连传导途径的数量都是可控的。

The electronics of the future could be built

未来的电子技术元件可以用

to use this perfectly efficient electron highway.

这个高效的电子高速路建成。

The topological properties of subatomic particles

亚原子粒子的拓扑学属性

could also transform quantum computing.

也可以为量子计算带来革命。

Quantum computers take advantage of the fact

量子计算机利用亚原子粒子

that subatomic particles can be in different states at the same time

可以同时处于不同状态这一事实，

to store information in something called qubits.

将信息存储在量子位上。

These qubits can solve problems exponentially faster

这些量子位与传统数码电脑相比，

than classical digital computers.

解决问题的速度可以呈指数增长。

The problem is that this data is so delicate

但问题是，这些数据实在是太脆弱，

that interaction with the environment can destroy it.

环境中轻微的干扰就会损坏它们。

But in some exotic topological phases,

但在某些特定的拓扑学相态中，

the subatomic particles can become protected.

亚原子粒子可以呈现出 一种被保护的状态。

In other words, the qubits formed by them

换句话说，这些由它们组成的量子位，

can't be changed by small or local disturbances.

不会因那些内部 的微小干扰而产生变化。

These topological qubits would be more stable,

这些拓扑学量子位将更加稳定，

leading to more accurate computation and a better quantum computer.

从而产生更精确的计算 和更好的量子计算机。

Topology was originally studied as a branch of purely abstract mathematics.

拓扑学起初是作为 纯抽象数学的分支来研究的。

Thanks to the pioneering work of Thouless, Haldane, and Kosterlitz,

由于Thouless，Haldane 和 Kosterlitz 所做的先驱工作，

we now know it can be used to understand the riddles of nature

我们现在知道了，拓扑学 可以帮助我们理解自然的奥秘，

and to revolutionize the future of technologies.

并且催生未来科技的巨变。