近日，中国科学院半导体研究所的马稳龙及其研究团队取得一项新进展。经过不懈努力，他们成功发展离散时间开放量子动力学中的亚稳态理论。相关研究成果已于2024年4月8日在国际知名学术期刊《物理评论A》上发表。

该研究团队成功构建了离散时间开放量子动力学中亚稳态的一般理论框架，采用序列重复量子信道进行描述。本文进一步将这一广义亚稳态理论应用于拉姆齐序列下目标系统上的一类典型量子信道，这些信道源于辅助量子比特与目标系统之间的纯移相耦合。通过将序列量子通道的平均动力学拆解为随机轨迹，研究人员预测并数值验证了有趣的亚稳态行为。此外，研究还探讨了带有辅助量子比特的目标量子系统，在量子态和动力学工程中的实际应用案例。

据悉，在开放系统动力学中，亚稳态是指系统在衰减至渐近稳定态之前，首先经历的一个长寿命的初始弛豫状态。这种现象在经典系统和量子系统的连续时间随机动力学中均有所发现。然而，值得注意的是，许多开放量子系统动力学的情境本质上具有离散性，并且每个离散时间区间的演化过程通常由任意量子信道来描述，而这些量子信道通常无法由连续时间主方程来生成。

附：英文原文

Title: Theory of metastability in discrete-time open quantum dynamics

Author: Yuan-De Jin, Chu-Dan Qiu, Wen-Long Ma

Issue&Volume: 2024/04/08

Abstract: Metastability in open system dynamics describes the phenomena of initial relaxation to long-lived metastable states before decaying to the asymptotic stable states. It has been found in continuous-time stochastic dynamics of both classical and quantum systems. However, many cases of open quantum system dynamics are intrinsically discrete, and the evolution within each discrete time interval is described by an arbitrary quantum channel, which often cannot be generated by continuous-time master equations. Here we develop a general theory of metastability in discrete-time open quantum dynamics, described by sequential repetitive quantum channels. We apply the general metastability theory to a typical class of quantum channels on a target system, induced by an ancilla qubit with a pure-dephasing coupling to the target system and under Ramsey sequences. Interesting metastable behaviors are predicted and numerically demonstrated by decomposing the average dynamics of sequential quantum channels into stochastic trajectories. We also present examples of applications in quantum state and dynamics engineering of a target quantum system with an ancilla qubit.

DOI: 10.1103/PhysRevA.109.042204

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.109.042204