By Ben Turner 18 days ago
作者:Ben Turner 18天前
The crystal is able to forever cycle between states without losing energy.
这种晶体能够在不损失能量的情况下永远在各种状态之间循环。
The time crystal was created inside Google's Sycamore chip,which is kept cool inside their quantum cryostat.时间晶体是在谷歌的 Sycamore 芯片中制造出来的，它被保存在他们的量子低温恒温器中(Image credit:Eric Lucero/Google,Inc.)(图片来源:Eric Lucero/谷歌公司)
Researchers working in partnership with Google may have just used the tech giant's quantum computer to create a completely new phase of matter—a time crystal.
与谷歌合作的研究人员可能刚刚利用这家科技巨头的量子计算机创造了一个全新的物质阶段ーー时间晶体。
With the ability to forever cycle between two states without ever losing energy,time crystals dodge one of the most important laws of physics—the second law of thermodynamics,which states that the disorder,or entropy,of an isolated system must always increase.These bizarre time crystals remain stable,resisting any dissolution into randomness,despite existing in a constant state of flux.
由于时间晶体能够永远在两个状态之间循环而不会损失能量，因此时间晶体避开了最重要的物理定律之一----热力学第二定律定律，该定律指出，孤立系统的无序性或熵必须始终增加。这些奇异的时间晶体保持稳定，尽管处于不断变化的状态，却能抵抗任何随机的解体。
According to a research article posted July 28 to the preprint database arXiv,scientists were able to create the time crystal for roughly 100 seconds using qubits(quantum computing's version of the traditional computer bit)inside the core of Google's Sycamore quantum processor.
根据7月28日发布在预印数据库 arXiv 上的一篇研究文章，科学家们能够在谷歌 Sycamore 量子处理器的核心内使用量子位(传统计算机位的量子计算版本)创造出大约100秒的时间晶体。
The existence of this weird new matter phase,and the entirely new realm of physical behaviors it reveals,is incredibly exciting to physicists,especially as time crystals were only first predicted to exist just nine years ago.
这个奇怪的新物质阶段的存在，以及它揭示的物理行为的全新领域，对物理学家来说是令人难以置信的兴奋，尤其是时间晶体仅仅在9年前才被预测存在。
"This was a big surprise,"Curt von Keyserlingk,a physicist at the University of Birmingham in the U.K.who was not involved in the study,told Live Science."If you asked someone 30,20 or maybe even 10 years ago,they would not have expected this."
没有参与这项研究的英国伯明翰大学物理学家 Curt von Keyserlingk 告诉《生活科学》:"这是一个巨大的惊喜。"。"如果你在30年前、20年前、甚至10年前问某人，他们不会预料到会出现这种情况。"
Time crystals are fascinating objects to physicists because they essentially sidestep the second law of thermodynamics,one of the most ironclad laws in physics.It states that entropy(a rough analog for the amount of disorder in a system)always increases.If you want to make something more ordered,you need to put more energy into it.
对于物理学家来说，时间晶体是迷人的物体，因为它们基本上绕过了物理学中最严格的定律之一----热力学第二定律。它指出，熵(一个粗略的模拟量的无序在一个系统)总是增加。如果你想让一些东西更有序，你需要投入更多的精力。
This tendency for disorder to grow explains a lot of things,such as why it's easier to stir ingredients into a mixture than it is to separate them out again,or why headphone cords get so tangled in pants'pockets.It also sets the arrow of time,with the past universe always more ordered than the present;watching a video in reverse,for instance,is likely to look strange to you primarily because you're witnessing the counterintuitive reversal of this entropic flow.
这种无序增长的趋势可以解释很多事情，比如为什么将原料搅拌到混合物中比将它们分离出来更容易，或者为什么耳机线会如此纠结在裤子口袋里。它还设置了时间之箭，过去的宇宙总是比现在更有序;例如，看一个反向的视频，可能看起来很奇怪，主要是因为你正在目睹这个熵流的反直觉逆转。
The second law of thermodynamics says that all systems evolve toward a state of more disorder,where energy is shared out evenly across the system.热力学第二定律认为，所有的系统都进化到一种更加无序的状态，能量在系统中均匀分配(Image credit:Universal History Archive/Universal Images Group via Getty Images)
Time crystals don't follow this rule.Instead of slowly approaching thermal equilibrium—"thermalizing"so that their energy or temperature is equally distributed throughout their surroundings,they get stuck between two energy states above that equilibrium state,cycling back and forth between them indefinitely.
时间晶体不遵循这个规则。它们并没有慢慢接近热平衡----"热化"使得它们的能量或温度在周围环境中均匀分布，而是被卡在高于平衡状态的两个能量状态之间，无限期地来回循环。
To explain how deeply unusual this behavior is,von Keyserlingk said to picture a sealed box filled with coins before being shaken a million times.As the coins ricochet from,and bounce around,each other,they"become more and more chaotic,exploring all of the sorts of configurations that they can explore"until the shaking stops,and the box is opened to reveal the coins in a random configuration,with roughly half of the coins facing up and half facing down.We can expect to see this random,half-up,half-down endpoint regardless of the way we first arranged the coins in the box.
为了解释这种行为有多么不寻常，冯·凯塞林克说想象一个装满硬币的密封盒子在被摇晃一百万次之前的样子。随着硬币互相跳跃和反弹，它们"变得越来越混乱，探索各种可以探索的结构"，直到震动停止，盒子被打开，显示出硬币的随机结构，大约一半的硬币面朝上，一半面朝下。我们可以期待看到这个随机的，半上半下的端点，不管我们第一次在盒子里放硬币的方式。
Inside the"box"of Google's Sycamore,we can view the quantum processor's qubits much like we would our coins.In the same way that the coins can be either heads or tails,qubits can be either a 1 or a 0—the two possible positions in a two-state system—or a weird mix of the probabilities of both states called a superposition.What's weird about time crystals,von Keyserlingk says,is that no amount of shaking,or zapping from one state to another,can move the time crystal's qubits into the lowest energy state,which is a random configuration;they can only flip it from its starting state to its second state,then back again.
在谷歌 Sycamore 的"盒子"中，我们可以像查看硬币一样查看量子处理器的量子位。就像硬币可以是正面也可以是反面一样，量子比特可以是1或0——两态系统中的两个可能位置——也可以是两种状态概率的奇怪组合，称为叠加态。冯·凯塞林克说，关于时间晶体的奇怪之处在于，无论多少震动，或从一种状态转换到另一种状态，都不能使时间晶体的量子位进入最低能量状态，这是一种随机构型;它们只能将时间晶体从起始状态翻转到第二种状态，然后再翻转回来。
"It just sort of flip-flops,"von Keyserlingk said."It doesn't end up looking random,it just gets jammed stuck.It's like it remembers what it looked like initially,and it repeats that pattern over time."
"这只是一种人字拖,"冯·凯塞林克说。"它看上去不是随机的，而是卡住了。就像它能记住最初的样子，并且随着时间的推移不断重复这种模式。"
In this sense,a time crystal is like a pendulum that never stops swinging.
在这个意义上，时间晶体就像一个永不停止摆动的钟摆。
"Even if you totally physically isolate a pendulum from the universe,so there's no friction and no air resistance,it will eventually stop.And that's because of the second law of thermodynamics,"Achilleas Lazarides,a physicist at the University of Loughborough in the U.K.who was among the scientists to first discover the theoretical possibility of the new phase in 2015,told Live Science."Energy starts out concentrated in the pendulum's center of mass,but there's all of these internal degrees of freedom—like the ways the atoms can vibrate inside the rod—that it will eventually be transferred into."
"即使你从物理上将钟摆从宇宙中完全隔离出来，因此没有摩擦和空气阻力，钟摆最终也会停止。他是2015年第一批发现新阶段理论可能性的科学家之一，他告诉《生活科学》杂热力学第二定律。"能量一开始集中在钟摆的质心，但所有这些内部自由度都存在ーー就像原子在棒内振动的方式ーー它最终会被传递进去。"
In fact,there's no way for a large-scale object to behave like a time crystal without sounding absurd,because the only rules that enable time crystals to exist are the spooky and surreal rules that govern the world of the very small—quantum mechanics.
事实上，对于一个大尺度的物体来说，它的行为就像一个时间晶体一样，而不会听起来很荒谬，因为使时间晶体存在的唯一规则就是支配着这个非常小的量子力学世界的幽灵般的、超现实的规则。
In the quantum world,objects behave both like point particles and little waves at the same time,with the magnitude of these waves in any given region of space representing the probability of finding a particle at that location.But randomness(such as random defects in a crystal's structure or a programmed randomness in the interaction strengths between qubits)can cause a particle's probability wave to cancel itself out everywhere apart from one very small region.Rooted in place,unable to move,change states or thermalize with its surroundings,the particle becomes localized.
在量子世界中，物体同时具有点粒子和小波的行为，在任何给定的空间区域，这些波的大小代表在该位置发现粒子的概率。但是随机性(例如晶体结构中的随机缺陷或量子比特之间相互作用强度的程序化随机性)可以导致粒子的概率波在除了一个非常小的区域之外的任何地方抵消掉。粒子生根于原地，不能移动，不能改变状态，不能与周围环境热化，从而形成局部化。
Otherworldly 'time crystal' made inside Google quantum computer could change physics forever
(Image credit: Eric Lucero/Google, Inc.) Researchers working in partnership with Google may have just used the tech giant's quantum computer to create a completely new phase of matter - a time crystal.
The researchers used this localization process as the foundation of their experiment.Using 20 strips of superconducting aluminum for their qubits,the scientists programmed each one into one of two possible states.Then,by blasting a microwave beam over the strips,they were able to drive their qubits to flip states;the researchers repeated the experiment for tens of thousands of runs and stopped at different points to record the states their qubits were in.What they found was that their collection of qubits was flipping back and forth between only two configurations,and the qubits weren't absorbing heat from the microwave beam either—they had made a time crystal.
研究人员把这个本地化过程作为他们实验的基础。科学家们用20条超导铝条作为量子位，将每一条编程成两种可能的状态之一。然后，通过在条带上发射微波束，他们能够驱动量子位翻转状态;研究人员重复这个实验数以万计的运行，并在不同的点停下来记录他们的量子位的状态。他们发现，他们收集的量子位只在两种构型之间来回翻转，而且这些量子位也不吸收微波束的热量ーー他们制造了一个时间晶体。
They also saw a key clue that their time crystal was a phase of matter.For something to be considered a phase,it usually has to be very stable in the face of fluctuations.Solids will not melt if the temperatures around them vary slightly;neither will slight fluctuations cause liquids to evaporate or freeze suddenly.In the same way,if the microwave beam used to flip the qubits between states was adjusted to be close to but slightly off from the exact 180 degrees needed for a perfect flip,the qubits still nonetheless flipped to the other state.
他们还发现了一个关键的线索，那就是他们的时间晶体是物质的一个相。对于被认为是一个阶段的东西，它通常必须在波动面前非常稳定。如果周围的温度变化不大，固体就不会融化;微小的波动也不会导致液体突然蒸发或结冰。同样的，如果用来在状态之间翻转量子位的微波束被调整到接近但略微偏离完美翻转所需的精确180度，量子位仍然翻转到另一个状态。
"It's not the case that if you're not exactly at the 180 degrees you will scramble them,"Lazarides said."It[the time crystal]magically will always tip a bit in,even if you're making slight mistakes."
拉扎里德斯说:"如果温度没有达到180华氏度，它们就不会被搅乱。"。"即使你犯了一些小错误，时间晶体也会神奇地向里面倾斜一点。"
Another hallmark of moving from one phase to another is the breaking of physical symmetries,the idea that the laws of physics are the same for an object at any point in time or space.As a liquid,the molecules in water follow the same physical laws at every point in space and in every direction,but cool water down enough so that it transforms into ice and its molecules will pick regular points along a crystal structure—or lattice—to arrange themselves across.Suddenly,the water molecules have preferred points in space to occupy,and they leave the other points empty—the spatial symmetry of the water has been spontaneously broken.
从一个阶段移动到另一个阶段的另一个标志是打破物理对称性，即物理定律在时间或空间的任何点都是相同的。作为一种液体，水中的分子在空间的每一点和每一个方向都遵循着相同的物理定律，但是将水冷却到足以使其变成冰，它的分子将沿着晶体结构(或晶格)挑选规则的点来排列自己。突然之间，水分子在空间中占据了优先的位置，而让其他位置处于空白状态----水的空间对称性被自发地打破了。
In much the same way that ice becomes a crystal in space by breaking with spatial symmetry,time crystals become crystals in time by breaking with time symmetry.At first,before their transformation into the time crystal phase,the row of qubits will experience a continuous symmetry between all moments in time.But the periodic cycle of the microwave beam chops the constant conditions experienced by the qubits down into discrete packets(making the symmetry imposed by the beam a discrete time-translation symmetry).Then,by flipping back and forth at twice the period of the wavelength of the beam,the qubits break with the discrete time-translation symmetry imposed by the laser.They are the first objects we know of that are able to do this.
就像空间中的冰由于空间对称性的破坏而成为晶体一样，时间晶体也由于时间对称性的破坏而在时间上成为晶体。首先，在它们转变为时间晶体相之前，一排量子位将在时间的所有时刻之间经历一个连续对称。但是，微波束的周期循环将量子位元所经历的恒定条件削减为离散数据包(使得微波束施加的对称性具有离散时间平移对称性)。然后，通过在两倍于光束波长周期的位置来回翻转，量子位就会破坏由激光施加的离散时间平移对称性。它们是我们知道的第一个能够做到这一点的物体。
All of this weirdness makes time crystals rich in new physics,and the control that Sycamore provides researchers beyond other experimental setups could make it an ideal platform for further investigation.That's not to say it cannot be improved,however.Like all quantum systems,Google's quantum computer needs to be perfectly isolated from its environment to prevent its qubits from undergoing a process called decoherence,which eventually breaks down the quantum localization effects,destroying the time crystal.The researchers are working on ways to better isolate their processor and mitigate the impact of decoherence,but it's unlikely they will eliminate the effect for good.
所有这些奇怪的现象使得时间晶体在新的物理学中变得丰富多彩，Sycamore 公司提供给研究人员的控制超越了其他实验装置，这使得它成为进一步研究的理想平台。然而，这并不是说它不能被改进。像所有的量子系统一样，谷歌的量子计算机需要完全隔离它的环境，以防止它的量子比特经历一个被称为退相干的过程，这个过程最终打破了量子定位效应，破坏了时间晶体。研究人员正在研究如何更好地隔离处理器并减轻退相干的影响，但是他们不太可能消除这种影响。
Despite this,Google's experiment is likely to remain the best way to study time crystals for the foreseeable future.Though numerous other projects have succeeded in making what convincingly appear to be time crystals in other ways—with diamonds,helium-3 superfluids,quasiparticles called magnons and with Bose-Einstein condensates—for the most part the crystals produced in these setups dissipate too quickly for detailed study.
尽管如此，在可预见的未来，谷歌的实验可能仍将是研究时间晶体的最佳方式。尽管许多其他项目已经成功地以其他方式制造出令人信服的时间晶体——用钻石、氦-3超流体、被称为磁性粒子的准粒子以及玻色-爱因斯坦凝聚体——但在大多数情况下，这些凝聚体所产生的晶体消散得太快，无法进行详细研究。
The theoretical newness of the crystals is in some ways a double-edged sword,as physicists currently struggle to find clear applications for them,although von Keyserlingk has suggested that they could be used as highly accurate sensors.Other proposals include using the crystals for better memory storage or for developing quantum computers with even faster processing power.
这种晶体在理论上的新奇在某种程度上是一把双刃剑，因为物理学家们目前正在努力为它们找到明确的应用，尽管冯·凯塞林克认为它们可以用作高精度的传感器。其他的建议包括使用晶体来更好的存储记忆，或者开发具有更快处理能力的量子计算机。
But in another sense,the greatest application of time crystals may already be here:They allow scientists to probe the boundaries of quantum mechanics.
但从另一方面来说，时间晶体最大的应用可能已经在这里了:它们使科学家能够探索量子力学的边界。
"It allows you to not just study what shows up in nature,but to actually design it and look at what quantum mechanics lets you do and doesn't let you do,"Lazarides said."If you don't find something in nature then it doesn't mean it can't exist—we just created one of those things."
它不仅能让你研究自然界中出现的东西，还能让你设计它，看看量子力学能让你做什么，不能让你做什么。"如果你在自然界中找不到什么东西，那并不意味着它不存在ーー我们只是创造了其中之一。"
Originally published on Live Science.
最初发表在 Live Science 上。
来源：
https://www.livescience.com/google-invents-time-crystal
