Dissipative quantum backflow

Abstract

Dissipative backflow is studied in the context of open quantum systems. This theoretical analysis is carried out within two frameworks, the effective time-dependent Hamiltonian due to Caldirola–Kanai (CK) and the Caldeira–Leggett (CL) one where a master equation is used to describe the reduced density matrix in the presence of dissipation and temperature of the environment. Two examples are considered: the free evolution of one and two Gaussian wave packets and the time evolution under a constant field. Backflow is shown to be reduced with dissipation and temperature but never suppressed. Interestingly enough, quantum backflow is observed when considering both one and two Gaussian wave packets within the CL context. Surprisingly, in both cases, the backflow effect seems to be persistent at long times. Furthermore, the constant force $\mathrm{mg}\ge 0$ behaves against backflow. However, the classical limit of this quantum effect within the context of the classical Schrödinger equation is shown to be present. Backflow is also analyzed as an eigenvalue problem in the CK framework. In the free propagation case, eigenvalues are independent on mass, Planck constant, friction and its duration, but, in the constant force case, eigenvalues depend on a factor which itself is a combination of all of them as well as the force constant.