FPGA-based adaptive control for phase stabilization in fiber-optic interferometers using correlated photons

Time-bin encoded photon pairs enable robust, decoherence-resistant transmission through optical fibers for long-distance quantum communication, where phase noise poses a critical limitation to stable operation. Here, we implement an adaptive perturbation-and-observe algorithm on a fully digital FPGA platform operating with real-time feedback at 1 Hz. The control signal is derived from the coincidence counts of correlated photon pairs. This adaptive approach reduces the rise time by 70 % and the coincidence noise by 30 %, resulting in visibility improvements sustained for more than 600 s. These results provide an efficient solution for long-term phase stabilization in quantum and photonic systems.