Quantum-Relay-Assisted Key Distribution over High Photon Loss Channels

中继量子信息

Relaying Quantum Information

本文研究量子中继信道中的信息传输，提出支持不同纠缠拓扑的部分解码—转发框架，统一分析纠缠辅助与无辅助通信并恢复已知结果。

State redistribution as merging: introducing the coherent relay

State redistribution allows one party to optimally send part of her state to another party. Here we show that this can be derived simply from two applications of coherent state-merging. This provides a protocol whereby a middle party acts as a relay station to help another party more efficiently transfer quantum states. This also gives a protocol for state splitting and the reverse Shannon theorem (assisted or unassisted by side information), and allows one to use less classical communication for partial state-merging using a sub-protocol we call ebit repackaging. Thus state-merging generates …

Environment-assisted bosonic quantum communications

We consider a quantum relay which is used by two parties to perform several continuous-variable protocols of quantum communication, from entanglement distribution (swapping and distillation), to quantum teleportation, and quantum key distribution. The theory of these protocols is suitably extended to a non-Markovian model of decoherence characterized by correlated Gaussian noise in the bosonic environment. In the worst case scenario where bipartite entanglement is completely lost at the relay, we show that the various protocols can be reactivated by the assistance of classical (separable) corr…

Multi-Hop Quantum Key Distribution with Passive Relays over Underwater Turbulence Channels

Absorption, scattering, and turbulence experienced in underwater channels severely limit the range of quantum communications. In this paper, to overcome range limitations, we investigate a multi-hop underwater quantum key distribution (QKD) where intermediate nodes help the key distribution between the source and destination nodes. We consider deployment of passive-relays which simply redirect the qubits to the next relay node or receiver without any measurement. Based on near-field analysis, we present the performance of relay-assisted QKD scheme in clear ocean under different atmospheric con…

使用相干态叠加的无噪声线性放大与容损量子中继

Noiseless Linear Amplification and Loss-Tolerant Quantum Relay using Coherent State Superpositions

提出一种基于相干态叠加的多光子量子剪刀遥放大器推广方案，实现完美保真度的无噪声线性放大，并证明其可作为多进制相移键控相干态的容损量子中继及用于连续变量纠缠提纯。