Transport of pseudothermal photons through an anharmonic cavity

Under nonequilibrium conditions, quantum optical systems reveal unusual properties that might be distinct from those in condensed matter. The fundamental reason is that photonic eigenstates can have arbitrary occupation numbers, whereas in electronic systems these are limited by the Pauli principle. Here, we address the steady-state transport of pseudothermal photons between two waveguides connected through a cavity with Bose-Hubbard interaction between photons. One of the waveguides is subjected to a broadband incoherent pumping. We predict a continuous transition between the regimes of Lorentzian and Gaussian chaotic light emitted by the cavity. The rich variety of nonequilibrium transport regimes is revealed by the zero-frequency noise. There are three limiting cases, in which the noise-current relation is characterized by a power-law, S proportional to J gamma. The Lorentzian light corresponds to Breit-Wigner-like transmission and gamma =2. The Gaussian regime corresponds to many-body transport with the shot noise (gamma =1) at large currents; at low currents, however, we find an unconventional exponent gamma =3/2 indicating a nontrivial interplay between multi-photon transitions and incoherent pumping. The nonperturbative solution for photon dephasing is obtained in the framework of the Keldysh field theory and Caldeira-Leggett effective action. These findings might be relevant for experiments on photon blockade in superconducting qubits, thermal states transfer, and photon statistics probing.

Automated summary

Under nonequilibrium conditions, quantum optical systems exhibit distinct properties due to the arbitrary occupation numbers of photonic eigenstates, unlike in condensed matter systems limited by the Pauli principle. The study of pseudothermal photon transport between waveguides connected through a cavity reveals a continuous transition between Lorentzian and Gaussian chaotic light emission, characterized by the zero-frequency noise and power-law noise-current relation. The nonperturbative solution for photon dephasing provides insights for experiments involving photon blockade in superconducting qubits, thermal states transfer, and photon statistics probing.