Realization of nonreciprocal photon statistics by manipulating the quantum nonlinearity of cold atoms in an asymmetric cavity

In a strongly coupled cavity quantum electrodynamics (QED) system, the second- order correlation function g ( 2 ) ( r ) of the transmitted probe light from the cavity is determined by the nonlinearity of the atom in the cavity. Therefore, the system provides a platform for controlling the photon statistics by manipulating nonlinearity. In this paper, we experimentally demonstrate nonreciprocal quantum statistics in a cavity QED system with several atoms strongly coupled to an asymmetric optical cavity, which is composed of two mirrors with different transmittivities. When the direction of the probe light is reversed, the intracavity light field alternates to a different level. Distinct photon statistics are then observed due to the quantum nonlinearity associated with strongly coupled atoms. Sub-Poissonian photon-number statistics for forward light and a Poissonian distribution for backward light are then realized. Our work provides an effective approach for realizing nonreciprocal quantum devices, which have potential applications in the unidirectional generation of nonclassical light fields and quantum sensing. (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement