谁懂这个给讲讲?中国科学家成功实现反事实量子通信

来源: 2017-05-19 06:21:15 [] [旧帖] [给我悄悄话] 本文已被阅读: 次 (15034 bytes)
中国科学家成功实现反事实量子通信
 
 

据物理学家组织网近期报道,中国科学技术大学研究人员成功实现直接反事实量子通信,在不发送任何物理粒子的情况下将一幅黑白位图从一个地点传送到另一个地点,这在通信史上尚属首次。该研究由中国科学技术大学、中科大上海研究所以及清华大学的中国科学家合作设计和实验,用嵌套式的量子芝诺效应成功实现反事实通信。

反事实性在两个地点之间需要一种量子通道,这意味着量子微粒穿过此通道的可能性极小,如果能够穿过,会丢弃此系统的运行,而开启一个新运行系统。因为波粒二象性使其运作,但是波粒二象性是粒子物理学的基础:粒子可以单独由波函数来描述。

换言之,量子芝诺效应发生在不稳定的量子系统被反复的测量。在量子世界,观测或测量系统会导致系统发生改变,在本例中,不稳定的粒子在反复观测时将永远不会衰减。量子芝诺效应创造了一个具有高可能性的事实上冻结的系统。研究报告发表在《美国国家科学院院刊》上。


(Phys.org)—In the non-intuitive quantum domain, the phenomenon of counterfactuality is defined as the transfer of a quantum state from one site to another without any quantum or classical particle transmitted between them. Counterfactuality requires a quantum channel between sites, which means that there exists a tiny probability that a quantum particle will cross the channel—in that event, the run of the system is discarded and a new one begins. It works because of the wave-particle duality that is fundamental to particle physics: Particles can be described by wave function alone. 





Well understood as a workable scheme by physicists, theoretical aspects of counterfactual communication have appeared in journals, but until recently, there have been no practical demonstrations of the phenomenon. Now, a collaborative of Chinese scientists has designed and experimentally tested a counterfactual communication system that successfully transferred a monochrome bitmap from one location to another using a nested version of the quantum Zeno effect. They have reported their results in the Proceedings of the National Academy of Sciences. 

The quantum Zeno effect occurs when an unstable quantum system is subjected to a series of weak measurements. Unstable particles can never decay while they are being measured, and the system is effectively frozen with a very high probability. This is one of the implications of the well known but highly non-intuitive principle that looking at something changes it in the quantum realm. 

Using this effect, the authors of the new study achieved direct communication between sites without carrier particle transmission. In the setup they designed, two single-photon detectors were placed in the output ports of the last of an array of beam splitters. According to the quantum Zeno effect, it's possible to predict which single-photon detector will "click" when photons are allowed to pass. The system's nested interferometers served to measure the state of the system, thereby preventing it from changing.

Alice transfers a single photon to the nested interferometer; it is detected by three single photon detectors, D0, D1 and Df. If D0 or D1 click, Alice concludes a logic result of one or zero. If Df clicks, the result is considered inconclusive, and is discarded in post-processing. After the communication of all bits, the researchers were able to reassemble the image—a monochrome bitmap of a Chinese knot. Black pixels were defined as logic 0, while white pixels were defined as logic 1.

The idea came from holography technology. The authors write, "In the 1940s, a new imaging technique—holography—was developed to record not only light intensity but also the phase of light. One may then pose the question: Can the phase of light itself be used for imaging? The answer is yes." In the experiment, the phase of light itself became the carrier of information, and the intensity of the light was irrelevant to the experiment. 

The authors note that besides applications in quantum communication, the technique could be used for such activities as imaging ancient artifacts that would be damaged by directly shining light. 

Explore further: A quantum effect allows infrared measurements to be performed by detecting visible light 

More information: Direct counterfactual communication via quantum Zeno effect. PNAS 2017 ; published ahead of print April 25, 2017, DOI: 10.1073/pnas.1614560114

Abstract 
Intuition from our everyday lives gives rise to the belief that information exchanged between remote parties is carried by physical particles. Surprisingly, in a recent theoretical study [Salih H, Li ZH, Al-Amri M, Zubairy MS (2013) Phys Rev Lett 110:170502], quantum mechanics was found to allow for communication, even without the actual transmission of physical particles. From the viewpoint of communication, this mystery stems from a (nonintuitive) fundamental concept in quantum mechanics—wave-particle duality. All particles can be described fully by wave functions. To determine whether light appears in a channel, one refers to the amplitude of its wave function. However, in counterfactual communication, information is carried by the phase part of the wave function. Using a single-photon source, we experimentally demonstrate the counterfactual communication and successfully transfer a monochrome bitmap from one location to another by using a nested version of the quantum Zeno effect.

所有跟帖: 

看英文就明白了,是利用波做介质,中国媒体故意炒作反事实这个噱头忽悠人 -austraveller- 给 austraveller 发送悄悄话 austraveller 的博客首页 austraveller 的个人群组 (0 bytes) () 05/19/2017 postreply 07:49:33

你认为 counterfactuality 怎么翻比较好? -jsl609- 给 jsl609 发送悄悄话 jsl609 的个人群组 (0 bytes) () 05/19/2017 postreply 17:20:28

如果是真的,这个做到了真正的量子通信。即,把纠缠的两个量子事先分发给两个地点。 -手心手背99- 给 手心手背99 发送悄悄话 手心手背99 的个人群组 (455 bytes) () 05/19/2017 postreply 08:39:28

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