Practical decoy-state measurement-device-independent quantum key distribution

TL;DR

This paper develops tight formulas for decoy-state MDI-QKD using only vacuum+weak decoy states, improving security analysis and approaching theoretical limits, while also accounting for finite data fluctuations.

Contribution

It provides the first complete analysis of decoy-state MDI-QKD with vacuum+weak decoy states, including finite-size effects, enhancing practical security.

Findings

Tight bounds for yield and error rate with vacuum+weak decoy states.

Method approaches the theoretical limit with infinite decoy states.

Finite data fluctuations are effectively incorporated into the analysis.

Abstract

Measurement-device-independent quantum key distribution (MDI-QKD) is immune to all the detection attacks; thus when it is combined with the decoy-state method, the final key is unconditionally secure, even if a practical weak coherent source is used by Alice and Bob. However, until now, the analysis of decoy-state MDI-QKD with a weak coherent source is incomplete. In this paper, we derive, with only vacuum+weak decoy state, some tight formulas to estimate the lower bound of yield and the upper bound of error rate for the fraction of signals in which both Alice and Bob send a single-photon pulse to the untrusted third party Charlie. The numerical simulations show that our method with only vacuum+weak decoy state can asymptotically approach the theoretical limit of the infinite number of decoy states. Furthermore, the statistical fluctuation due to the finite length of date is also considered based on the standard statistical analysis.