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.

中文翻译：

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非线性奇偶时间对称腔中的鲁棒光子传输

探索了耦合腔的非线性奇偶-时间（PT）-对称系统中的光子传输，该系统包含取决于腔内光子的非线性增益和损耗。提出了一种基于量子Langevin方程的分析方法，以研究传统方案的阻尼动力学，从而通过根据耦合强度调节输入频率来获得最佳效率。在非线性PT对称方案中，发现非线性增益饱和会导致系统达到仍然包含PT对称性的稳态，并且稳态本征频率会自动调整为非线性增益饱和以实现最佳传递效率。结果，获得的光子传输效率与耦合强度无关，是鲁棒的，这改善了常规方案的结果。同时，弱耦合状态下的饱和增益与稳态下的损耗不匹配，表现出自发的PT对称破坏。PT断裂状态下相应的转移效率根据偶联强度而降低。该方案提供了一种理论上的建议，以模拟腔中的光子传输以实现鲁棒的效率。