Cavity-based optical switching via phase modulation in warm rubidium vapor

Optical switching remains a key outstanding challenge for scalable photonic quantum computing due to the trade-off between speed, bandwidth, and loss. Quantum photonics demands all three to enable high computational clock rates and resource-efficient scaling to large systems. We present a cavity-based optical switch that overcomes this limitation, demonstrating a rise time of 22 ns, an insertion loss of 2.4 dB, and an extinction ratio of 17.5, which bridges the gap between speed and efficiency in photonic switching. All-optical control is achieved via phase modulation of a signal field detuned from the near-degenerate two-photon absorption ladder in warm rubidium vapor. The ultimate performance of our switch will find applications in active multiplexing, loop-based quantum memory, and feed-forward for quantum error-correction protocols.