论文标题
预测多体量子系统中不完美的回声动力学
Predicting Imperfect Echo Dynamics in Many-Body Quantum Systems
论文作者
论文摘要
回声协议提供了一种研究宏观过程中时间箭头的方法。从非平衡状态开始，正在研究的多体量子系统在一定时间段内$τ$。此后，执行（有效的）时间逆转，如果实现完美地实现 - 将系统带回了另一个时间段$τ$之后的初始状态。典型的例子是核磁共振成像和极化回波实验。在向后传播期间，存在小的，不受控制的不准确性导致“回声信号”与原始进化的偏差，并且可以被利用以量化非平衡状态的不稳定性和动力学的不可逆性。我们得出了该回波信号对宏观可观察物的典型依赖性的分析预测，该预测是在不准确的幅度和该过程的持续时间$τ$上的分析预测，并在数值示例中对其进行了验证。
Echo protocols provide a means to investigate the arrow of time in macroscopic processes. Starting from a nonequilibrium state, the many-body quantum system under study is evolved for a certain period of time $τ$. Thereafter, an (effective) time reversal is performed that would -- if implemented perfectly -- take the system back to the initial state after another time period $τ$. Typical examples are nuclear magnetic resonance imaging and polarization echo experiments. The presence of small, uncontrolled inaccuracies during the backward propagation results in deviations of the "echo signal" from the original evolution, and can be exploited to quantify the instability of nonequilibrium states and the irreversibility of the dynamics. We derive an analytic prediction for the typical dependence of this echo signal for macroscopic observables on the magnitude of the inaccuracies and on the duration $τ$ of the process, and verify it in numerical examples.
