Long distance measurement-device-independent quantum key distribution with coherent-state superpositions

TL;DR

This paper demonstrates that using coherent-state superpositions in measurement-device-independent quantum key distribution significantly enhances security distance and key rate, especially over long distances, compared to traditional weak coherent states.

Contribution

The paper introduces a novel application of coherent-state superpositions as a source in MDI-QKD and provides analytical formulas for parameter estimation, improving long-distance security.

Findings

Enhanced security transmission distance with CSS

Increased secure key rate using CSS

Effective parameter estimation with Chernoff bound

Abstract

Measurement-device-independent quantum key distribution (MDI-QKD) with decoy-state method is believed to be securely applied to defeat various hacking attacks in practical quantum key distribution systems. Recently, the coherent-state superpositions (CSS) have emerged as an alternative to single-photon qubits for quantum information processing and metrology. Here, in this Letter, CSS are exploited as the source in MDI-QKD. We present an analytical method which gives two tight formulas to estimate the lower bound of yield and the upper bound of bit error rate. We exploit the standard statistical analysis and Chernoff bound to perform the parameter estimation. Chernoff bound can provide good bounds in the long distance MDI-QKD. Our results show that with CSS, both the security transmission distance and secure key rate are significantly improved compared with those of the weak coherent states in the finite-data case.