Loss-induced suppression, revival, and switch of photon blockade

Loss-induced transparency (LIT), featuring the revival of optical intensity by adding loss, has been demonstrated in classical optics. However, a fundamental question has remained unexplored, i.e., during the process of LIT, whether quantum correlations of the photons can also be revived or even tuned by increasing the loss. Here we find that, accompanying classical LIT in a nonlinear optical-molecule system, a purely quantum effect as photon blockade (PB) indeed can be revived with the help of loss. In particular, a quantum critical point emerges in the system: below the point, adding loss leads to the suppression of optical intensity and its correlations; in contrast, by surpassing the point, PB is revived and enhanced with more losses. Also, a quantum switch between single-PB and two-PB can be realized by simply tuning the loss. Our work provides a counterintuitive strategy to engineer quantum devices in a practical lossy environment.