Wang Tie-Jun, Wang Chuan
Opt Express. 2015 Nov 30;23(24):31550-63. doi: 10.1364/OE.23.031550.
We illustrate an entanglement distillation protocol (EDP) for a mixed photon-ensemble which composed of four kinds of entangled states and vacuum states. Exploiting the linear optics and local entanglement resource (four-qubit entangled GHZ state), we design the nondemolition parity-checking and qubit amplifying (PCQA) setup for photonic polarization degree of freedom which are the key device of our scheme. With the PCQA setup, a high-fidelity entangled photon-pair system can be achieved against the transmission losses and the decoherence in noisy channels. And in the available purification range for our EDP, the fidelity of this ensemble can be improved to the maximal value through iterated operations. Compared to the conventional entanglement purification schemes, our scheme largely reduces the initialization requirement of the distilled mixed quantum system, and overcomes the difficulties posed by inherent channel losses during photon transmission. All these advantages make this scheme more useful in the practical applications of long-distance quantum communication.
我们展示了一种用于由四种纠缠态和真空态组成的混合光子系综的纠缠蒸馏协议（EDP）。利用线性光学和局部纠缠资源（四量子比特纠缠GHZ态），我们为光子偏振自由度设计了非破坏奇偶校验和量子比特放大（PCQA）装置，这是我们方案的关键器件。通过PCQA装置，针对噪声信道中的传输损耗和退相干，可以实现高保真纠缠光子对系统。并且在我们的EDP的可用纯化范围内，通过迭代操作可以将该系综的保真度提高到最大值。与传统的纠缠纯化方案相比，我们的方案大大降低了蒸馏混合量子系统的初始化要求，并克服了光子传输过程中固有信道损耗带来的困难。所有这些优点使得该方案在长距离量子通信的实际应用中更有用。
