Transport of pseudothermal photons through an anharmonic cavity

Abstract

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