Quantum Information Processing Based On The Creation And Measurement Of Coherent Light Phase

Coherent states are paid more and more attentions from many researchers because they are more robustness and more easily to be obtained than single photon resource. Owing to the character of approximately orthogonality and overcomplete, coherent states can be used as quantum encoded bit in the quantum information processing tasks. Besides, coherent states can also be used as quantum bus because they can interact with single photon through Kerr media or interact with atoms through cavity input-output process.The coherent states involved in this paper are totally used as the quantum bus, which will be measured after the interaction with photons or atoms for the purpose of obtaining the information of photons or atoms. The main content of our paper is as follows(i) cross-Kerr nonlinearity:We propose two protocols to generate four-photon polarized entanglement state. The first one takes advantage of an idea of circulation to achieve a higher success probability. The second one is a feasible and economic protocol because it successfully avoids the minus conditional phase shift and reduces the number of Kerr nonlinearity. Then, with the aid of cross-Kerr nonlinearity, we propose a simplified symmetry analyzer which is more economic than the former one because we reduce two cross-Kerr nonlinearities, more feasible because we do not need minus conditional phase shift induced by cross-Kerr nonlinearity, more accurate because the error probability is lower with the same parament. Next, We construct Bell state nondestructive analysis and GHZ state nondestructive analysis based on this simplified symmetry analyzer.(ii) cavity input-output process:We firstly design a atomic state entangler with the low-Q cavity intermediate coupling region and discuss the success probability and fidelity of the entangler. With this atomic state entangler, Bell state nonlocal analysis, quantum state transfer, atomic|X> state, Cluster state, GHZ state, and quantum logic controlled-NOT gate can be well realized.