Non-Hermitian interacting quantum walks of correlated photons

The non-Hermitian skin effect (NHSE), referring to the anomalous localization of eigenstates, has been widely discussed in single-particle systems. However, the interplay between the interacting NHSE and the quantum optical phenomena remains elusive. Here, We present the non-Hermitian quantum walks of strongly correlated photon pairs. Through studying the dynamic behavior of the photon pairs in the nonreciprocal Bose-Hubbard chain, we theoretically demonstrate the interplay between interactions and the NHSE. When launching two non-entangled photons, the photons exhibit the nonreciprocal bunching effect, which can be suppressed by the interactions. When launching two path-entangled photons, the interactions can not only suppress but reverse the nonreciprocal bunching. In stark contrast to the common wisdom that the NHSE suppresses the entanglement of the quantum many-body system, the entanglement of the photons here can be significantly enhanced. Our results reveal that many-body interactions and entanglement significantly restrain the non-Hermitian nonreciprocal quantum dynamics, offering insights into the interplay between many-body quantum entanglement and non-Hermitian physics.