Post-measurement pairing quantum key distribution: a study on the feasibility of practical field deployment

Abstract

Quantum Key Distribution (QKD) has emerged as a solution for secure communication that is resilient against attacks from quantum computers. However, its widespread deployment remains constrained by fundamental trade-offs between secret key rates, communication distances and practical security. Emerging new protocols, namely the measurement-device independent (MDI)-QKD, propose to mitigate these challenges through the use of interference detection over an untrusted intermediate node–which aim to mitigate channel losses and detection vulnerabilities in long-distance quantum communication. In this work, we investigate the implementation of protocols with such interference techniques. We begin with a critical comparison study between selected MDI-QKD protocol variants, and identify post-measurement pairing (PMP)-QKD as a promising candidate. In particular, PMP-QKD has critical advantage of simple implementation, i.e. avoiding stringent experimental requirements such as global phase stabilisation. Subsequently, building on the theoretical framework by Zhou et al. [1], we developed a detailed simulation code that optimises the secret key rate as a function of communication distance. This framework incorporates key experimental parameters including signal intensities, pulse probability distributions, and pairing interval thresholds. Finally, we apply our simulation to a practical deployment scenario within Singapore’s National Quantum Safe Network (NQSN) testbed, estimating realistic system parameters. Our results demonstrate that PMP-QKD can achieve high secret key rates, surpassing the repeaterless secret key capacity under field conditions. This work affirms the theoretical benefits of PMP-QKD and provides critical insights for its real-world deployment, positioning it as a strong candidate for long distance quantum communication not only across Singapore’s quantum network but also possible quantum networks with neighbouring countries in the future as well.