Photon blockade is the result of the interplay between the quantized nature of light and strong optical nonlinearities, whereby strong photon-photon repulsion prevents a quantum optical system from absorbing multiple photons. We theoretically study a single atom coupled to the light field, described by the resonantly driven Jaynes-Cummings model, in which case the photon blockade breaks down in a second-order phase transition at a critical drive strength. We show that this transition is associated to the spontaneous breaking of an antiunitary $\mathcal{PT}$ symmetry. Within a semiclassical approximation, we calculate the expectation values of observables in the steady state. We then move beyond the semiclassical approximation and approach the critical point from the disordered (blockaded) phase by reducing the Lindblad quantum master equation to a classical rate equation that we solve. The width of the steady-state distribution in Fock space is found to diverge as we approach the critical point with a simple power law, allowing us to calculate the critical scaling of steady-state observables without invoking mean-field theory. We propose a simple physical toy model for biased diffusion in the space of occupation numbers, which captures the universal properties of the steady state. We list several experimental platforms where this phenomenon may be observed.

中文翻译：

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破坏光子阻断的批判理论

光子阻滞是光的量子化性质与强光学非线性之间相互作用的结果，强光子与光子之间的排斥力阻止了量子光学系统吸收多个光子。我们从理论上研究了共振驱动的Jaynes-Cummings模型所描述的与光场耦合的单个原子，在这种情况下，光子阻滞在临界驱动强度下发生了二级相变。我们证明了这种转变与抗unit药的自发破坏有关$\mathcal{PT}$对称。在半经典近似值内，我们计算稳态下可观测值的期望值。然后，我们超越半经典近似，通过将Lindblad量子主方程简化为我们求解的经典速率方程，从无序（阻塞）相逼近临界点。当我们通过简单的幂定律接近临界点时，发现Fock空间中稳态分布的宽度有所不同，这使我们无需引用均值场理论即可计算稳态可观测值的临界比例。我们提出了一个简单的物理玩具模型，用于在占领数空间中进行有向扩散，该模型捕获了稳态的普遍性质。我们列出了可以观察到这种现象的几个实验平台。