单光子空间W态的高效无噪线性放大方案
摘要
<p indent="0mm">Single photon spatial-mode entanglement is an important resource in quantum communication, which is widely used in quantum teleportation, quantum secure direct communication, quantum repeater, quantum key distribution and so on. The single-photon spatial-mode W state is an important single-photon multi-mode entanglement. However, when distributing the single-photon spatial-mode W state in practical imperfect quantum channels, the transmission loss caused by the channel noise will cause the photon to decay exponentially with the growth of channel length. Based on quantum non-cloning theorem, we cannot accurately copy the quantum state. The photon transmission loss will largely reduce quantum communication’s efficiency, and even threaten its security. As a result, the photon transmission loss is a big obstacle for the practical development of long-distance quantum communication. Noiseless linear amplification (NLA) is a promising method to solve the photon transmission loss problem, which can herald the existence of the target photon without destroying it. In order to protect the single-photon spatial-mode W state from photon transmission loss, we propose an NLA protocol scheme for the single-photon spatial-mode W state based on the high-efficient quantum scissor (QS) with local squeezing operation. In this protocol, each remote communication party needs to operate a high-efficient QS with local squeezing operation simultaneously. Only when all the quantum scissors are successfully operated, the NLA protocol for the single-photon spatial-mode W state will be successful. By adjusting the transmittance of the variable beam splitter (VBS) in each QS, one can increase the fidelity of the target single-photon spatial-mode W state. The total success probability and amplification factor of our NLA protocol depend on the transmittance of VBS, the photon transmission efficiency, and the squeezing parameter. Comparing with the NLA protocol with conventional QSs