Long-Distance Trust-Free Quantum Key Distribution

TL;DR

This paper explores the integration of measurement-device-independent QKD with quantum repeaters to enable trust-free, long-distance quantum key distribution, analyzing key rates and system parameters for practical implementation.

Contribution

It proposes a combined MDI-QKD and quantum repeater framework for trust-free long-distance QKD and evaluates its performance considering realistic device imperfections.

Findings

Maximum secure distance depends on system parameters and number of quantum memories.

Optimized parameters significantly improve key rates and achievable distances.

The approach demonstrates feasibility for practical trust-free quantum communication networks.

Abstract

The feasibility of trust-free long-haul quantum key distribution (QKD) networks is addressed. We combine measurement-device-independent QKD (MDI-QKD), as an access technology, with a quantum repeater setup, at the core of future quantum communication networks. This will provide a quantum link none of whose intermediary nodes need to be trusted, or, in our terminology, a trust-free QKD link. As the main figure of merit, we calculate the secret key generation rate when a particular probabilistic quantum repeater protocol is in use. We assume the users are equipped with imperfect single photon sources, which can possibly emit two single photons, or laser sources to implement decoy-state techniques. We consider apparatus imperfection, such as quantum efficiency and dark count of photodetectors, path loss of the channel, and writing and reading efficiencies of quantum memories. By optimizing different system parameters, we estimate the maximum distance over which users can share secret keys when a finite number of memories are employed in the repeater setup.