高阶相干光子扣除超叠加改善量子传输保真度

The High-Order Coherent Superposition of Photon-Subtraction for Improving the Fidelity of Teleportation

利用光子扣除算符构成的相干光子超叠加操作作用于2个模压缩真空态,引入一类非高斯量子态——高阶相干光子扣除超叠加单模压缩真空态.通过导出该量子态的正规乘积形式,推导了该量子态的归一化系数,与Legendre多项式密切相关.利用相干态的超完备关系和平移算符的正规乘积,导出了态的特征函数的相干态表示,进而解析导出了利用该量子态作为纠缠源实现相干态隐形传输的保真度.研究结果表明:当压缩参数相等时,保真度可获得最大值,对于奇数阶操作,保真度比无叠价操作情况更差,而对于偶数阶情况,在一定的压缩参数范围内,保真度优于无纠缠情况,且保真度可优于经典的最大保真度1/2,同时保真度可以随m的增加而改善.

A kind of non-Gaussian quantum state with continuous variable by operating high-order coherent superposition of photon-subtraction on two single-mode squeezed vacuum states has been introduced.Using the normally ordering form of squeezing operation and completeness relation of coherent state representation,the analytical expression of normalized factor of this new state has been derived.It is found that the factor is related to Legendre polynomials.Based on the teleportation scheme of Kimble-Brauntein,the fidelity for teleporting coherent state by using the new entangled state as entangled resource has been calculated.It is shown that：（i）the fidelity has a maximum value when r1=r2;（ii）the fidelity becomes worse than that from the case without coherent superposition operation for odd m;while for even m,the fidelity can be improved in a certain small squeezing parameter region,and even exceeds 1/2.In addition,the fidelity increases as even m in a certain region.