Long-distance twin-field quantum key distribution with entangled sources

TL;DR

This paper proposes a long-distance twin-field quantum key distribution protocol using entangled coherent states, significantly extending transmission range and demonstrating robustness against practical imperfections, advancing secure quantum communication.

Contribution

Introduces a novel TFQKD scheme with entangled coherent states to surpass existing distance limits and improve robustness against errors.

Findings

The protocol achieves a theoretical distance advantage of 400 km.

It shows strong robustness against misalignment errors.

Simulation results confirm improved performance over traditional TFQKD.

Abstract

Twin-field quantum key distribution (TFQKD), using single-photon-type interference, offers a way to exceed the rate-distance limit without quantum repeaters. However, it still suffers from the photon losses and dark counts, which impose an ultimate limit on its transmission distance. In this letter, we propose a scheme to implement TFQKD with an entangled coherent state source in the middle to increase its range, as well as comparing its performance under coherent attacks with that of TFQKD variants. Simulations show that our protocol has a theoretical distance advantage of 400 kilometers. Moreover, the scheme has great robustness against the misalignment error and finite-size effects. Our work is a promising step toward long-distance secure communication and is greatly compatible with future global quantum network.