Parity-Time (PT) symmetric quantum mechanics is a complex extension of conventional Hermitian quantum mechanics, in which physical observables possess a real eigenvalue spectrum. In this context, quantum effects have special, counterintuitive features, that are ultimately due to the underlying PT-symmetric structure of the theory, and in particular, the presence of losses in the system.
In our recent work, we have shown, theoretically, and experimentally, how the presence of losses in a passive PT-symmetric optical system affects quantum optical phenomena, such as the Hong-Ou-Mandel (HOM) quantum interference. In particular, we have observed, that the position of the HOM dip is counterintuitively shifted to shorter propagation distances, with respect to the Hermitian case. This, ultimately, is due to the fact, that, although neither of the photons are lost during propagation in the system, the sole presence of loss in it is enough to significantly modify the propagation dynamics of photons.
Check out the details in our preprint available here