Luo Xi-Wang, Zhang Chuanwei, Du Shengwang
Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080-3021, USA.
Phys Rev Lett. 2022 Apr 29;128(17):173602. doi: 10.1103/PhysRevLett.128.173602.
The emergence of parity-time (PT) symmetry has greatly enriched our study of symmetry-enabled non-Hermitian physics, but the realization of quantum PT symmetry faces an intrinsic issue of unavoidable symmetry-breaking Langevin noises. Here we construct a quantum pseudo-anti-PT (pseudo-APT) symmetry in a two-mode bosonic system without involving Langevin noises. We show that the spontaneous pseudo-APT symmetry breaking leads to an exceptional point, across which there is a transition between different types of quantum squeezing dynamics; i.e., the squeezing factor increases exponentially (oscillates periodically) with time in the pseudo-APT-symmetric (broken) region. Such dramatic changes of squeezing factors and quantum dynamics near the exceptional point are utilized for ultraprecision quantum sensing. These exotic quantum phenomena and sensing applications can be experimentally observed in two physical systems: spontaneous wave mixing nonlinear optics and atomic Bose-Einstein condensates. Our Letter offers a physical platform for investigating exciting APT symmetry physics in the quantum realm, paving the way for exploring fundamental quantum non-Hermitian effects and their quantum technological applications.
宇称-时间（PT）对称性的出现极大地丰富了我们对对称性驱动的非厄米物理的研究，但量子PT对称性的实现面临着不可避免的对称性破缺朗之万噪声这一固有问题。在此，我们在一个双模玻色子系统中构建了一种不涉及朗之万噪声的量子伪反PT（pseudo-APT）对称性。我们表明，自发的伪APT对称性破缺会导致一个例外点，在该点两侧存在不同类型的量子压缩动力学之间的转变；即，在伪APT对称（未破缺）区域，压缩因子随时间呈指数增长（周期性振荡）。例外点附近压缩因子和量子动力学的这种显著变化被用于超精密量子传感。这些奇异的量子现象和传感应用可以在两个物理系统中通过实验观测到：自发波混频非线性光学和原子玻色-爱因斯坦凝聚体。我们的论文提供了一个用于研究量子领域中令人兴奋的APT对称物理的物理平台，为探索基本的量子非厄米效应及其量子技术应用铺平了道路。
