Quantum squeezing and sensing with anti-parity-time symmetric quantum optics

Abstract

Non-Hermitian optics with parity-time (PT) or anti-parity-time (APT) symmetry with controlled gain and loss has resulted in many interesting phenomena that do not necessarily have corresponding counterparts in conservative systems. If such a system enters quantum region, the gain-loss induced unavoidable Langevin noises does not preserve the symmetry. Here, we demonstrate APT symmetric nonlinear optical four-wave mixing (FWM) without involving gain and loss, and thus no Langevin noises are induced. We show that The APT phase transition across the exceptional point is connected to the generation of two-mode light squeezing: In the APT symmetry broken regime the squeezing factor oscillates and is bounded, while in the APT symmetry region the squeezing factor increase exponentially along propagation direction. We will discuss how to implement this dramatic change of quantum squeezing for precision quantum sensing.