LAUSR

Photon transfer in the nonlinear parity–time (PT)‐symmetry system of coupled cavities, which contains nonlinear gain and loss dependent on the intracavity photons, is explored. An analysis based on quantum Langevin equations is presented to study damping dynamics of the conventional scheme, which results in an optimal efficiency by tuning the input frequency dependent on the coupling strength. In the nonlinear PT‐symmetric scheme, it is found that the nonlinear gain saturation can cause the system to reach the steady state that still contains the PT symmetry, and the steady‐state eigenfrequencies self‐adjust to the nonlinear gain saturation for an optimal transfer efficiency. As a consequence, the photons transfer efficiency obtained is robust independent on the coupling strength, which improves the results of the conventional scheme. Meanwhile, the saturated gain in the weak coupling regime does not match the loss in the steady state, exhibiting an appearance of a spontaneous PT symmetry‐breaking. The corresponding transfer efficiency in the PT‐broken regime decreases dependent on the coupling strength. This scheme provides a theoretical proposal to simulate photon transfer in cavities for achieving a robust efficiency.