Efficient quantum space-division multiplexing using time-bin and phase encoding in few-mode fibers

Space-division multiplexing using multimode optical fibers has been applied to quantum-level signals with time-bin and phase encoding, achieving megaqubits per second over 8 km of few-mode fiber. Time windowing is efficiently employed to eliminate modal crosstalk between quantum channels. The dead time of the single-photon detectors in each quantum channel, typically regarded as a bottleneck in quantum transmission, is synchronized with the time-window intervals, thereby optimizing the detection rates.