Mitigating phase correlations in quantum key distribution using path-selection modulation
Phys. Rev. Applied 25, 034060 – Published 18 March, 2026
DOI: https://doi.org/10.1103/vkyv-snfg
Abstract
Phase correlations are an underexplored vulnerability in quantum key distribution. Here, we present an experimental and simulated characterization of correlations arising from electro-optic phase encoding, over repetition rates up to the GHz level. To mitigate this vulnerability (and all side channels arising from active phase modulators), we propose a “path-selection modulation” source that eliminates the need for active phase modulation altogether. Encoding is achieved by randomly selecting between multiple paths, each path corresponding to one of the desired encoded states. Phase randomization is achieved using gain switching. We characterize this source at a clock rate of 1 GHz.
