Performance of the BB84 protocol without decoy states under varying announcement structures

This is the authors' abstract. We don't add key points for this paper.

In phase-randomized weak coherent pulse (WCP) implementations of the quantum key distribution (QKD) BB84 protocol, the decoy method is often used to compensate BB84's vulnerability against photon number splitting attacks. However, this typically introduces extra complexities and requirements on experimental devices. In this paper, we are therefore interested in phase-randomized WCP implementations without the decoy method. We examine the performance of three QKD protocols with different classical announcement structures, namely, BB84, SARG04, and No Public Announcement of Basis (NPAB) BB84, using numerical security proof techniques. Key rates are computed using the software [J. Burniston ., software , ver. 2.0.2 (2024)]. We compare secure key rates of the three protocols in asymptotic and finite-size regimes for lossy and noisy channels. The three protocols show different relative advantages depending on the channel behavior. Canonical BB84 shows robustness against errors and depolarization, SARG04 demonstrates resilience against high-loss channels, and NPAB BB84 shows potential advantages against physical misalignment between QKD devices.