论文标题
经典辐射宏观自旋的量子纠缠状态
Quantum entangled states of a classically radiating macroscopic spin
论文作者
论文摘要
纠缠构成了将量子与古典物理学区分开的主要特征，并且是量子技术的关键资源。但是，我们在这里表明，纠缠也可能是复合非线性辐射系统中经典行为出现的基本要素。我们考虑了来自宏观自旋发射极的辐射，例如来自原子集合的集体辐射。我们引入了一类新的宏观自旋状态，即相干辐射的自旋状态（CRS），该状态定义为SU（2）降低操作员的渐近特征状态。我们发现，CRSS中的自旋发射极会辐射经典的相干光，尽管CRS本身是一种量子纠缠的状态，表现出旋转挤压。我们进一步表明，CRS自然是在Dicke上级产生的，并且是Dicke相变的基础。因此，我们的CRSS理论为研究辐射的量子物理学提供了新的概念，并在当前平台中应用涉及原子或旋转集合，它们在量子技术（例如计量和激光）中的考虑以及自旋系统的多体理论。
Entanglement constitutes a main feature that distinguishes quantum from classical physics and is a key resource of quantum technologies. Here we show, however, that entanglement may also serve as the essential ingredient for the emergence of classical behavior in a composite nonlinear radiating system. We consider the radiation from a macroscopic spin emitter, such as the collective radiation from an atomic ensemble. We introduce a new class of macroscopic spin states, the coherently radiating spin states (CRSS), defined as the asymptotic eigenstates of the SU(2) lowering operator. We find that a spin emitter in a CRSS radiates classical-like coherent light, although the CRSS itself is a quantum entangled state exhibiting spin squeezing. We further show that CRSS are naturally produced in Dicke superradiance and underlie the dissipative Dicke phase transition. Our CRSS theory thus provides new concepts for studying the quantum physics of radiation, with applications in current platforms involving collections of atoms or spins, their consideration in quantum technologies such as metrology and lasing, and the many-body theory of spin systems.
