量子纠缠态的制备和应用

The use of entangled photons in quantum communication and related areas has been explored; an experiment demonstrating "backward time telegraphy" has been performed, and the first all-fiber quantum key distribution system in China realized. For the above experiments we developed our own single photon detectors, a random number generator，data processing hardware and software, etc. A new method based on entangled photon pairs for the absolute self-calibration of the quantum efficiency of single photon detectors (without the need of a second detector) has been proposed, patent pending. On the theoretical side, we have analyzed the nonclassical statistical properties of various quantum binomial states, and suggested a means for their preparation. A new "matrix realignment" method to distinguish between entangled and separable states has been constructed which is simple, directly computable and powerful; it can even recognize most of the bound entangled states that previously all other criteria could not distinguish; an estimate of the degree of entanglement can also be obtained. For the propagation of light pulses in a dispersive medium we propose a realistic physical model in which all the monochromatic modes of the pulse are "released" at an instantaneous moment, each travelling at its own phase velocity, so that the phenomena of "superluminal" propagation is actually the result of their superposition and interference; the speed of information transfer is limited by the phase velocity and not the group velocity.

以光参量下转换生成的孪生光子对为EPR源，可探讨纠缠态的量子本质。本项目研究多光子啦男灾始捌涫笛椴治鲆运庾泳啦靥宓牡ス庾悠裉冻檀吻逶冻檀械挠泄馗拍睿员愣云涓玫囟云浣锌袒杓坪侠淼氖笛榉桨福⒆钪赵谑笛樯鲜迪帧１鞠钅恳蔡教志啦钠渌蔷涮卣骷捌淝痹谟τ谩?.