Round-Robin Differential Phase-Time-Shifting Protocol for Quantum Key Distribution: Theory and Experiment

Year: 2021

Authors: Wang K.; Vagniluca I.; Zhang J.; Forchhammer So.; Zavatta A.; Christensen J.B.; Bacco D.

Autors Affiliation: The State Key Lab of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876, Chinaa; Department of Photonics Engineering, Technical University of Denmark, Kgs. Lyngby, 2800, Denmark; Consiglio Nazionale Delle Ricerche, Istituto Nazionale di Ottica (CNR-INO), Florence, 50125, Italy; Department of Physics Ettore Pancini, University of Naples Federico II, Naples, 80126, Italy; LENS and Department of Physics, University of Florence, Sesto Fiorentino, 50019, Italy; Danish Fundamental Metrology, Hshrsholm, 2970, Denmark

Abstract: Quantum key distribution (QKD) allows the establishment of common cryptographic keys among distant parties. Many of the QKD protocols that were introduced in the past, involve the challenge of monitoring the signal disturbance over the communication line, in order to evaluate the information leakage to a potential eavesdropper. Recently, a QKD protocol that circumvents the need for monitoring signal disturbance, has been proposed and demonstrated in initial experiments. Here, we propose an improved version of this so-called round-robin differential phase-shifting (RRDPS) protocol, in which both time and phase degrees of freedom are utilized to enlarge the Hilbert-space dimensionality, without increasing experimental complexity or relaxing security assumptions. We derive the security proofs of the round-robin differential phase-time-shifting (RRDPTS) protocol in the collective attack scenario, and benchmark it against RRDPS for different experimental parameters. Furthermore, a proof-of-concept experiment of the RRDPTS protocol, using weak coherent pulses and decoy state method, is demonstrated over 80 km of fiber link. Our results show that the RRDPTS protocol can achieve higher secret key rate in comparison with the RRDPS, in the condition of high quantum bit error rate.


Volume: 15 (4)      Pages from: 044017-1  to: 044017-11

More Information: This work is supported by CSC Funding and by NSFC (Grant No. 61831003) , by the Center of Excellence SPOCSilicon Photonics for Optical Communications (Ref. DNRF123) , by the EraNET Cofund Initiatives QuantERA within the European Union?s Horizon 2020 Research and Innovation Program Grant Agreement No. 731473 (Project SQUARE) , and by the NATO Science for Peace and Security program under Grant No. G5485.
KeyWords: quantum cryptography
DOI: 10.1103/PhysRevApplied.15.044017