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USTV Firstly Develops Non-local Quantum Simulator and Verifies Superluminal Phenomena in Parity-time World

release time:2016-08-11   Click on:1770

The quantum information key laboratory of Chinese Academy of Sciences leaded by Guo Guangcan, the professor of USTV and academician of Chinese Academy of Sciences, obtains significant progress in quantum simulator study. Professor Li Chuanfeng research team develops non-local quantum simulator and simulates the superluminal phenomena in parity-time world.The achievement firstly demonstrates the significant function of non-locality in quantum simulator, which breaks out the new studying direction for quantum simulator development. This achievement is published in on 8th August.
    

Quantum simulator is the dedicate quantum computer for solving certain problem, which was firstly proposed by Feynman in 1981. Currently people pay more attention to quantum acceleration capability of quantum simulator, the more quantum bit numbers being manipulated, the stronger of the arithmetic capability will be. Researches show that if the manipulated quantum bit numbers reaches around 30, the arithmetic capability of quantum simulator can be stronger than ordinary classical computers. So far, around 10 quantum bits can be manipulated in experiment. The study firstly reveals another significant advantage of quantum simulator, which is non-locality of quantum. Non-local quantum simulator can be used for studying some basic problems of quantum physics that cannot be solved by typical computer in principle.
     

Parity-time (PT) symmetry theory is proposed by American physicist Bender and other physicists in 2002 for the promotion of quantum mechanics. We know that quantum mechanics is based on a series of assumptions, so which of these assumptions can broaden? Bernder and others think that the assumption on hermiticity of Hamiltonian is too strict, which can broaden to be replaced by PT symmetric assumption, e.g. assuming that Hamiltonian has space - time inversion symmetry. According to this theory, the quantum world we know is just a special case of PT world (with Hermitian). Li Chuanfeng research team simulates such a PT world in experiment. They bisect the entangled photons and distribute to two laboratories with 25 meters distance for building non-local quantum simulator. In addition to entangled photon pairs, their quantum simulator also consists of a series of quantum logic gates and post-selection operation. Through the post-selection (50% success rate), they conduct PT symmetric evolution of a photon from the entangled photon pairs. Quantum simulation result shows that PT symmetric evolution of the photon can make the information transmitted from one laboratory to another in a light speed exceeding 1.9 times by using "spooky action at a distance"of quantum entanglement. But the result further proves the overall information transmission speed cannot exceed the speed of light if considering the entire system (including the success and failure part).
    

The achievement shows the significant role of non-local quantum simulator in studying quantum physics basic problems, and reveals two basic and interesting issues at the same time: Firstly, whether a quantum system appropriate for PT symmetric evolution can be found in the real world? If yes, super light communication can possibly be proceed; Secondly, whether a theory more basic than quantum mechanics can be accommodated between "spooky action at a distance" with superlight communication.  
    

Associate professor Tang Jianshun and doctor Wang Yitao contributes equally as first authors of the article with theoretical part being completed by professor Han Yongjian. The job obtained finance from Ministry of Science and Technology of China, Natural Sciences Foundation, Chinese Academy of Sciences, Collaborative Innovation Center of Quantum Information and Frontier Quantum Science & Technology.


 

Experimental facility sketch

 

Sketch for superlight phenomenon in PT world 

Paper link:

http://www.nature.com/nphoton/journal/vaop/ncurrent/full/nphoton.2016.144.html 

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