研究光学非厄密哈密顿量的物理实现和其特性是目前感兴趣的课题，它可展现有趣的相变特性，能产生对光进行操控的新方法。其中宇称时间（PT）对称性的光学哈密顿量得到了广泛的关注，已经有很多基于固态体系的实验，但是尚未有在原子体系的实现，后者能将原子相干性和量子存储的概念引入，有望带来新的量子调控技术。另外，PT反对称体系与PT对称体系互补，能对光折射率的实部进行调控，但迄今为止也没有实验实现。本项目将采用一种全新的光耦合方式在原子中实现PT对称和反对称的哈密顿量，以及一般性的非厄密哈密顿量，研究其中的相变特性以及由此带来的若干新的光学现象。本项目将为光子光子相互作用提供新的实现机制，具有在量子信息领域的潜在应用，也为相变和拓扑特性等基础研究提供了新的平台。我们的研究打开了原子物理和PT对称性相结合的交叉领域，具有较好的发展前景。

Realization of optical non-Hermitian Hamiltonian is of great current interest, due to intriguing phase transition phenomena and opportunities for novel ways to control light. As a special category, parity-time symmetric Hamiltonian attracted much attention, and has been pursued in various solid state systems. Atomic systems have strong coherence and easily allow quantum information storage, and if they are integrated with PT symmetry, new techniques for quantum control of light and atoms should be expected. However, there has been no experimental implementation. Meanwhile, as a counterpart of PT symmetry, PT anti-symmetry is complementary as it can be used to manipulate the real part of refractive index, in contrast to the imaginary part in PT systems, and no realization has been reported either. In this proposal, we will apply a distinct light coupling mechanism and realize PT symmetric, PT anti-symmetric, and generic non-Hermitian Hamiltonians in an atomic vapor. Phase transition behavior and associated emerged new optical phenomena will be investigated. Our system provides new ways for photon-photon interaction which is useful for quantum information science, and it is also a platform to study phase transition and topology. The proposed work here will open up a promising field that combines atomic physics and the concepts of PT symmetry.