Ana Blázquez | Searcharxiv

arXiv2026

Simplified quantum key distribution implementation secure in the presence of state preparation flaws

We present an implementation of a three-state BB84 protocol with time-bin encoding, one decoy state and a simplified measurement scheme that uses passive basis choice. Our system simplifies the state characterization with respect to previous iterations. We also adapt the loss-tolerant method to our protocol, thus dealing with the measured state preparation flaws. We compare the obtained phase error rate and secret key rate when including the state imperfections and when assuming perfect states. Our results highlight the importance of characterization and implementation security.

quant-ph↗

arXiv2024

Evaluation of quantum key distribution systems against injection-locking attacks

While ideal quantum key distribution (QKD) systems are well-understood, practical implementations face various vulnerabilities, such as side-channel attacks resulting from device imperfections. Current security proofs for decoy-state BB84 protocols either assume uniform phase randomization of Alice's signals, which is compromised by practical limitations and attacks like injection locking, or rely on a (partially) characterized phase distribution. This work presents an experimental method to characterize the phase de-randomization from injection locking using a heterodyne detection setup, providing a lower bound on the degree of isolation required to protect QKD transmitters against injection-locking attacks. The methods presented are source-agnostic and can be used to evaluate general QKD systems against injection-locking attacks.

quant-ph↗