2020年12月13日15:02:07新闻新的基于光的量子计算机“九丈”已经取得了量子优势已关闭评论81145字数 5397阅读17分59秒阅读模式


A second type of quantum device performed a calculation impossible for a traditional computer



The quantum computer Jiuzhang works by sending particles of light(illustrated in red)into a network of channels and then measuring the photons at the other end.



A new type of quantum computer has proven that it can reign supreme,too.


A photonic quantum computer,which harnesses particles of light,or photons,performed a calculation that's impossible for a conventional computer,researchers in China report online December 3 in Science.That milestone,known as quantum supremacy,has been met only once before,in 2019 by Google's quantum computer(SN:10/23/19).Google's computer,however,is based on superconducting materials,not photons.


"This is the first independent confirmation of Google's claim that you really can achieve quantum supremacy,"says theoretical computer scientist Scott Aaronson of the University of Texas at Austin."That's exciting."

德克萨斯州大学奥斯汀分校的理论计算机科学家 Scott Aaronson :"这是第一次独立证实谷歌的声明,即你真的可以实现量子优势。""真令人兴奋。"

Named Jiuzhang after an ancient Chinese mathematical text,the new quantum computer can perform a calculation in 200 seconds that would take more than half a billion years on the world's fastest non-quantum,or classical,computer.


"My first impression was,'wow,'"says quantum physicist Fabio Sciarrino of Sapienza University of Rome.

罗马大学的量子物理学家 Fabio Sciarrino :"我的第一印象是''"

Google's device,called Sycamore,is based on tiny quantum bits made of superconducting materials,which conduct energy without resistance.In contrast,Jiuzhang consists of a complex array of optical devices that shuttle photons around.Those devices include light sources,hundreds of beam splitters,dozens of mirrors and 100 photon detectors.

谷歌的设备叫做 Sycamore,是基于超导材料制成的微小量子位,这种材料可以无阻力地传导能量。相比之下,玖章由一个复杂的光学装置阵列组成,光子可以穿梭于周围。这些设备包括光源、数百个分束器、几十个镜子和100个光子探测器。


The quantum computer Jiuzhang manipulates light via a complex arrangement of optical devices(shown).量子计算机玖章通过光学器件的复杂排列来操纵光(如图所示)HANSEN ZHONG 

Employing a process called boson sampling,Jiuzhang generates a distribution of numbers that is exceedingly difficult for a classical computer to replicate.Here's how it works:Photons are first sent into a network of channels.There,each photon encounters a series of beam splitters,each of which sends the photon down two paths simultaneously,in what's called a quantum superposition.Paths also merge together,and the repeated splitting and merging causes the photons to interfere with one another according to quantum rules.


Finally,the number of photons in each of the network's output channels is measured at the end.When repeated many times,this process produces a distribution of numbers based on how many photons were found in each output.


If operated with large numbers of photons and many channels,the quantum computer will produce a distribution of numbers that is too complex for a classical computer to calculate.In the new experiment,up to 76 photons traversed a network of 100 channels.For one of the world's most powerful classical computers,the Chinese supercomputer Sunway TaihuLight,predicting the results that the quantum computer would get for anything beyond about 40 photons was intractable.


While Google was the first to break the quantum supremacy barrier,the milestone is"not a single-shot achievement,"says study coauthor and quantum physicist Chao-Yang Lu of the University of Science and Technology of China in Hefei."It's a continuous competition between constantly improved quantum hardware and constantly improved classical simulation."After Google's quantum supremacy claim,for example,IBM proposed a type of calculation that might allow a supercomputer to perform the task Google's computer completed,at least theoretically.

尽管谷歌是第一个打破量子优势壁垒的,但这个里程碑"不是一次性的成就",研究合著者、中国科技大学量子物理学家陆说。"这是不断改进的量子硬件和不断改进的经典模拟之间的持续竞争。"例如,在谷歌宣称量子优势后,IBM 提出了一种计算方法,可能允许超级计算机执行谷歌计算机完成的任务,至少在理论上是这样。

And achieving quantum supremacy doesn't necessarily indicate that the quantum computers are yet very useful,because the calculations are esoteric ones designed to be difficult for classical computers.


The result does boost the profile of photonic quantum computers,which haven't always received as much attention as other technologies,says quantum physicist Christian Weedbrook,CEO of Xanadu,a Toronto-based company focused on building photonic quantum computers."Historically,photonics has been the dark horse."

量子物理学家克里斯蒂安·维德布鲁克是总部位于多伦多的 Xanadu 公司的首席执行官,该公司专注于建造光子量子计算机。"从历史上看,光子学一直是黑马。"

One limitation of Jiuzhang,Weedbrook notes,is that it can perform only a single type of task,namely,boson sampling.In contrast,Google's quantum computer could be programmed to execute a variety of algorithms.But other types of photonic quantum computers,including Xanadu's,are programmable.

维德布鲁克指出,九丈的一个局限性是它只能执行单一类型的任务,即玻色子取样。相比之下,谷歌的量子计算机可以被编程来执行各种算法。但是其他类型的光子量子计算机,包括 Xanadu 的,是可编程的。

Demonstrating quantum supremacy with a different type of device reveals how rapidly quantum computing is progressing,Sciarrino says."The fact that now the two different platforms are able to achieve this regime…shows that the whole field is advancing in a very mature way."

用不同类型的设备演示量子优势揭示了量子计算机的发展速度,Sciarrino 说。"事实上,现在两个不同的平台能够实现这一制度......表明整个领域正在以非常成熟的方式前进。"



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