Continuous variable measurement device independent quantum conferencing with postselection

• Published in: Scientific reports Vol. 12; no. 1; p. 17329
• Main Authors: Fletcher, Alasdair I., Pirandola, Stefano
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 15.10.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 639/624/1111; 639/766/483/481; Humanities and Social Sciences; multidisciplinary; Parameter estimation; Protocol; Reconciliation; Science; Science (multidisciplinary); Sensors; Values
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-022-22251-8

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.