Continuous-variable measurement device independent quantum conferencing with post-selection

TL;DR

This paper presents a continuous-variable measurement device independent quantum conferencing protocol with post-selection, improving key rates over longer distances in multi-party quantum communication.

Contribution

It introduces a novel post-selection method in CV-MDI quantum conferencing, enhancing rate-distance performance compared to non-post-selected protocols.

Findings

Positive key rate achieved over 6 km in symmetric configuration

Post-selection improves rate-distance performance

Trade-off between longer distance performance and shorter distance efficiency

Abstract

A continuous variable (CV), measurement device independent (MDI) quantum key distribution (QKD) protocol is analyzed, enabling three parties to connect for quantum conferencing. We utilise a generalised Bell detection at an untrusted relay and a postselection procedure, in which distant parties reconcile on the signs of the displacements of the quadratures of their prepared coherent states. We derive the rate of the protocol under a collective pure-loss attack, demonstrating improved rate-distance performance compared to the equivalent non-post-selected protocol. In the symmetric configuration in which all the parties lie the same distance from the relay, we find a positive key rate over 6 km. Such postselection techniques can be used to improve the rate of multi-party quantum conferencing protocols at longer distances at the cost of reduced performance at shorter distances.