论文标题

从量子相空间的角度来看概率滞后

Probabilistic Hysteresis from a Quantum Phase Space Perspective

论文作者

Bürkle, Ralf, Anglin, James R.

论文摘要

\ emph {概率滞后}是一个小的,孤立的经典系统中不可逆性的表现[Sci。 REP。9,14169]:在对控制参数的缓慢循环扫描后,微域合奏返回其初始能量的邻居的概率显着低于1。最近,在相应的量子系统中证实了类似的现象,因为粒子数量不太小$ n $。然而,在这种情况下,已经发现量子古典对应关系是非平凡的。控制参数变化的速率不能极为慢,并且能量的初始分布不得太窄。在本文中,我们直接通过利用husimi量子相空间形式主义来比较概率滞后的量子和经典形式。特别地,我们证明了经典的刺激性机制,这是经典概率滞后的关键成分,可以导致量子古典对应关系的分解,而不是量子成分。结果,即使运动方程中的量子校正与$ 1/n $成比例,因此存在很大的量子效应,因此天真的量子校正似乎很小。但是,我们还表明,通过平均能量上的平均能量恢复了量子构造,因此,对于足够的初始能量宽度和不太慢的扫描,毕竟恢复了经典结果。最后,我们表明,我们系统中经典和绝热极限的形式不可通信,导致准静态极限中量子古典对应关系的分解是由于宏观量子隧穿通过大型势垒。这解释了达到我们先前工作中报道的量子绝热限制所需的极慢扫描率。

\emph{Probabilistic hysteresis} is a manifestation of irreversibility in a small, isolated classical system [Sci. Rep. 9, 14169]: after a slow cyclic sweep of a control parameter, the probability that a microcanonical ensemble returns to the neighborhood of its initial energy is significantly below one. A similar phenomenon has recently been confirmed in a corresponding quantum system for not too small particle number $N$. Quantum-classical correspondence has been found to be non-trivial in this case, however; the rate at which the control parameter changes must not be extremely slow and the initial distribution of energies must not be too narrow. In this paper we directly compare the quantum and classical forms of probabilistic hysteresis by making use of the Husimi quantum phase space formalism. In particular we demonstrate that the classical ergodization mechanism, which is a key ingredient in classical probabilistic hysteresis, can lead to a breakdown of quantum-classical correspondence rather than to quantum ergodization. As a result strong quantum effects in the long-term evolution are present, even though the quantum corrections in the equations of motion are proportional to $1/N$ and therefore would naively seem to be small. We also show, however, that quantum ergodization is restored by averaging over energies, so that for sufficient initial energy width and not-too-slow sweep rate the classical results are recovered after all. Finally we show that the formal incommutability of the classical and adiabatic limits in our system, leading to the breakdown of quantum-classical correspondence in the quasi-static limit, is due to macroscopic quantum tunneling through a large energetic barrier. This explains the extremely slow sweep rates needed to reach the quantum adiabatic limit that were reported in our previous work.

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