Zhiyao Wang

We provide a security proof for quantum key distribution (QKD) protocols using passive detection setups within the entropic uncertainty relation (EUR) framework. Passive detection avoids the need for active basis choice but introduces challenges due to beam splitters and imperfections in detectors. We show how to define and bound the phase-error rate in passive detection setups, even when detector imperfections are not precisely known but lie within known ranges. Our analysis applies in the finite-size regime against general coherent attacks.

We examine the performance of three Quantum Key Distribution (QKD) protocols with different classical announcement structures, namely BB84, SARG04 and No Public Announcement of Basis (NPAB) BB84, using numerical security proof techniques. We simulate these protocols in a Weak Coherent Pulse (WCP) implementation in order to characterize their behaviour in a realistic implementation without decoy states. We vary the quantum channel characteristics and compare key rates of the three protocols in asymptotic and finite-size regimes. The three protocols show different relative advantages depending on the channel behaviour. Canonical BB84 shows robustness against errors and depolarization, SARG04 demonstrates resilience against high loss channels and NPAB BB84 shows potential advantages when we introduce physical misalignment between QKD devices.