Research Of Distillation And Amplification For Quantum Entangled State

Quantum mechanics provides more effective ways for communication and computation. Quantum computer becomes a new challenge for the classical encryption system with its ability of multi quantum state parallel computing. Thus, quantum communication has attracted more and more people’s attention because of its characteristics of absolute security. Entanglement has been regarded as a key source in the tasks of quantum communication. Single-photon entanglement is the simplest entanglement form. Nevertheless, environmental noise in the communication or transportation process is unavoidable, which will lead to the photon loss with some probability or create a partially entangled state from the maximally entangled state.As the decoherence from maximally entangled state to partially entangled state, he proposes an efficient entanglement concentration protocol(ECP) for an arbitrary entangled three-electron W state. This ECP has several advantages: Firstly, it do not require all the parties to participate in the whole process, and only two parties are needed to perform the operation. Secondly, the protocol can be repeated to obtain a high success probability.Noiseless linear amplification(NLA) is an effective way to protect the photon from loss. In this paper, he presents the existing optical quantum amplifier model and proposes two schemes on single-photon amplification and entanglement concentration. First, he proposed a practical linear optical amplification protocol based on local polarized Bell state, the most advantage of this protocol is that it not noly can increase the fidelity of the multi-mode single-photon W state, but also can perfectly protect the information encoded in the photon’s polarization degree of freedom. Second, he present an efficient approach to distill arbitrary single-photon entanglement assisted with polarized Bell states, this protocol has the full advantage of the protocol shown above, moreover, it can also distill partially entangled states to maximally entangled states. The two protocols described above are all based on linear optics which are feasible in current technology.In addition, he proposes an efficient quantum secure direct communication protocol based on linear optics and hybrid entanglement. In this protocol, it preforms near-deterministic hybrid Bell state analysis to read out information with very high success probability which can further improve the efficiency of quantum secure direct communication.