Entanglement assisted single-photon W state amplification

Photon loss is one of the main obstacles in long-distance quantum communication. In this paper, we propose a practical linear optical amplification protocol for the multi-mode single-photon W entangled state. Different from previous amplification protocols, we exploit the local polarized Bell states to complete the task. The most advantage of this protocol is that not only we can increase the fidelity of the multi-mode single-photo W state, but also can perfectly protect the information encoded in the photon's polarization degree of freedom. This protocol is based on the linear optics, which is feasible in current technology. Therefore, this protocol is helpful for future long-distance quantum communication.