论文标题
反馈引起的互动动力：统一但耗散的演变
Feedback-induced interactive dynamics: unitary but dissipative evolution
论文作者
论文摘要
物理系统的时间演变通常由微分方程描述，可以通过采用时空离散化来通过数值来求解。作为数值伪像，这种离散化在进化过程中导致累积错误通常在模拟中起负面作用。但是，在量子电路中，``进化时间''由电路层的深度表示，因此本质上是离散的。因此，其中的离散化诱导的误差不是数值伪像，而是导致常规量子动力学中不存在显着非平衡现象的物理观察效应。在本文中，我们表明，测量反馈和时间离散化的组合可以引起一种新型的量子动力学，其特征是单一但耗散的演变。作为这种统一但耗散进化的物理后果，在零维（单量）系统中揭示了具有自发对称性破坏的非平衡稳态。在一维互动量子系统中，还提出了与良好的安德森本地化中不同的定位机制。
The time evolution of a physical system is generally described by a differential equation, which can be solved numerically by adopting a difference scheme with space-time discretization. This discretization, as a numerical artifact, results in accumulated errors during evolution thus usually plays a negative role in simulations. In a quantum circuit, however, the ``evolution time'' is represented by the depth of the circuit layer, thus is intrinsically discrete. Hence, the discretization-induced error therein is not a numerical artifact, but a physical observable effect responsible for remarkable nonequilibrium phenomena absent in conventional quantum dynamics. In this paper, we show that the combination of measurement feedback and temporal discretization can give rise to a new type of quantum dynamics characterized by unitary but dissipative evolution. As physical consequences of such an unitary but dissipative evolution, a nonequilibrium steady state with spontaneous symmetry breaking is revealed in a zero-dimensional (single-qubit) system. A localization mechanism distinct from that in the well-established Anderson localization has also been proposed in an one-dimensional interactive quantum system.
