Theoretical model predicts single-photon-triggered avalanche in bistable cavity

The arXiv preprint (v1, 25 Jun 2026) models the cavity field with a quantum master equation that retains both quantum fluctuations and the discrete nature of the trigger photon. Numerical integration of the stochastic trajectories reveals that the probability of switching rises sharply when the drive is tuned near the bistability threshold, producing an output photon burst orders of magnitude larger than the input. This behavior maps onto a non-equilibrium phase-transition picture in which the single photon acts as a nucleation event that destabilizes the metastable low-photon state.

Because the work remains purely theoretical, no experimental parameters such as cavity decay rate or nonlinearity strength have yet been tested in the lab. Earlier semiclassical treatments of optical bistability omitted shot-noise effects that here prove essential for the avalanche statistics. Related cavity-QED experiments with Rydberg atoms or superconducting circuits have demonstrated related switching but at higher photon numbers, leaving the single-photon limit unprobed.

An all-optical single-photon avalanche detector is proposed as a direct application, yet the model assumes ideal coherent driving and lossless detection that real devices will violate. Realization will require cryogenic or integrated platforms with sub-microsecond reset times to avoid dark-count accumulation.

Next steps include mapping the switching probability versus detuning and photon number in a circuit-QED geometry, where single-photon sources and fast readout are already mature.