人机交互量子系统非平衡稳态中的自发对称破缺和局域化  

Spontaneous symmetry breaking and localization in nonequilibrium steady states of interactive quantum systems

作　　者：吴烁杭 蔡子 Shuohang Wu;Zi Cai(Wilczek Quantum Center and Key Laboratory of Artificial Structures and Quantum Control,School of Physics and Astronomy,Shanghai Jiao Tong University,Shanghai 200240,China;Shanghai Research Center for Quantum Sciences,Shanghai 201315,China)

机构地区：[1]Wilczek Quantum Center and Key Laboratory of Artificial Structures and Quantum Control,School of Physics and Astronomy,Shanghai Jiao Tong University,Shanghai 200240,China [2]Shanghai Research Center for Quantum Sciences,Shanghai 201315,China

出　　处：《Science Bulletin》2023年第18期2010-2016,M0003,共8页科学通报（英文版）

基　　金：supported by the National Key Research and Development Program of China(2020YFA0309000);the National Natural Science Foundation of China(12174251);the Natural Science Foundation of Shanghai(22ZR142830);Shanghai Municipal Science and Technology Major Project(2019SHZDZX01).

摘　　要：物理系统的时间演化一般用微分方程来描述,而数值求解微分方程往往需要将时空分立化,将微分方程变换成为差分方程,在这一分立化的过程往往伴随着累积误差的产生,进而降低模拟精度,但是,在量子电路计算系统中,“演化时间”表示量子线路的层数,只能取分立的数值。因此,在这类系统中,由时间分立化带来的累积误差不再是数值误差,而会带来物理上可观测的效果。本文提出了一种由反馈和时间分立化导致的新的量子动力学:人机交互量子动力学,这一动力学的特点是在保持了演化的么正性的前提下,系统能量不断耗散,最终达到一种非平衡稳态,这一非平衡稳态中可能涌现出超越平衡态框架的新的物理现象和物理机制,例如发生在零维系统的自发对称破缺,以及一种不同与安德森局域化的新的量子局域化机制。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 and 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,and 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.As physical consequences of this interactive quantum dynamics,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 a onedimensional interactive quantum system.

关 键 词：Interactive quantum dynamics Quantum feedback DISSIPATION LOCALIZATION 

分 类 号：O413[理学—理论物理]