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1、薛定谔猫的理论与实验薛定谔猫的理论与实验量子退相干量子退相干Nature 427,711-714(2004)薛定谔想要借此阐述的物理问题是:宏观世界是否也遵从适用于微观尺度的量子叠加原理。“薛定谔猫”佯谬巧妙地把微观放射源和宏观的猫联系起来,旨在否定宏观世界存在量子叠加态。随着量子力学的发展,科学家已先后通过各种方案获得了宏观量子叠加态。此前,科学家最多使个离子或个光子达到“薛定谔猫”态。但如何使更多粒子构成的系统达到这种状态并保存更长时间,已成为实验物理学的一大挑战。3Bohm的简化表述4t=0-5tT随着科学与技术的发展,这个理想实验被证实随着科学与技术的发展,这个理想实验被证实The G
2、reek LAOCOON-量子纠缠6HHadamardUCNOTThe EPR PairEinstein,Podolsky and Rosen,Phys.Rev.47,777(1935)Two Qubit GatesTwo Qubit GatesControlled NOT(CNOT)xCNOTHow to generate an entangled statexCNOTH两比特算法两比特算法-密集编码密集编码Superdense coding:AliceBobAlice is allowed to send only a single qubit.Can she transmit one o
3、f four different bits of information?Suppose Alice and Bob share the entangled state:Alice performs one of the following single qubit operations on her qubit:Alice sends her qubit to Bob.Bob performs a Bell state measurement.I,Z,X,iY9Bell states(entangled states):超光速通信超光速通信?纠缠光子对实验10相位匹配和能量守恒条件CD实验装
4、置11150mW diode70000 detected coincidences/sec12宏观粒子的波粒二象性-视频Other Qubits:Other Qubits:Atoms and ions in traps,photons,Q-dots,superconductorsAtoms and ions in traps,photons,Q-dots,superconductorsPhotons as flying qubitsQalgorithmSuperconducting qubit:Nakamura et al.Spin echo with sc-qubitBennet,Zeilinger,Zoller,Weinfurter et al.Two level systemFictitious spin 1/2Ion traps:J.I.Cirac and P.Zoller,Phys.Rev.Lett.74,4091(1995)Two QubitsTwo QubitsBasis:Bell states(entangled states):product state