Optimized attacks on twin-field quantum key distribution

Abstract

In twin-field quantum key distribution the two communicating parties, Alice and Bob, each send a weak coherent pulse to a third party stationed between them. The key bits are generated by interference between these pulses, with the results communicated to Alice and Bob. We consider optimized strategies for eavesdropping on the communication built upon state discrimination and quantum non-demolition measurements. We find that the best strategy comprises a two-step process but that even this does not compromise the security of the protocol.

Quantum key distribution and beyond: introduction

“…There is also an increasing interest in applying machine learning techniques to optimize the performance of QKD systems [5][6][7]. The security of practical implementations has also been addressed by devising hacking strategies [8][9][10], with their corresponding countermeasures, as well as by accounting for realistic imperfections and finite-key effects in the security analysis [2,11]. The feature issue also covers some less conventional protocols [12,13], relying on ambiguous state discrimination, as well as insight into multi-mode and high-dimensional QKD systems [14,15].…”