连续变量无条件纠缠交换 --纠缠态的量子离物传送

利用自行设计的两台非简并光学参量放大器，获得了一对具有经典相干性且量子起伏相互独立的连续变量纠缠态光场，并用它完成了连续变量的无条件纠缠交换，即纠缠态的量子离物传送．通过联合贝尔态探测与纠缠塌缩，使两个初始不纠缠而又从未发生过直接相互作用的光场产生了量子纠缠，其正交振幅和位相分量的量子起伏关联方差被直接测量，其测量值分别低于散离噪声极限1．23dB和1．12dB．理论计算与实验结果基本符合．

Unconditional entanglement swapping of continuous variables --quantum teleportation of entangled state

A pair of entangled states of light with classical coherence and independent quantum fluctuations has been produced from two home-designed and home-made non-degenerate optical parametric amplifiers. Utilizing these entangled states we have experimentally demonstrated unconditional entanglement swapping for continuous variables, i.e. quantum teleportation of an entangled state. Based on the direct detection of Bell states and entanglement collapse, two optical beams which have never directly interacted with each other are entangled together. The degrees of quantum correlation resulting from the entanglement swapping have been determined by direct measurement to be 1.23dB and 1.12dB below the shot noise limit for the amplitude and phase quadratures, respectively. The theoretical calculation and experimental measurements are in reasonable agreement.