Quantum current in dissipative systems

TL;DR

This paper develops a general theory for measuring quantum current in open systems, accounting for environmental effects, and demonstrates its application in a quantum ratchet model that reveals quantum contextuality and entanglement.

Contribution

It introduces a novel framework for experimentally measuring quantum current in dissipative systems, overcoming previous measurement challenges.

Findings

Current can be measured via weak and standard quantum measurements.

The model detects the onset of quantum contextuality.

Steady-state entanglement can be generated in hot environments.

Abstract

Describing current in open quantum systems can be problematic due to the subtle interplay of quantum coherence and environmental noise. Probing the noise-induced current can be detrimental to the tunneling-induced current and vice versa. We derive a general theory for the probability current in quantum systems arbitrarily interacting with their environment that overcomes this difficulty. We show that the current can be experimentally measured by performing a sequence of weak and standard quantum measurements. We exemplify our theory by analyzing a simple Smoluchowski-Feynman-type ratchet consisting of two particles, operating deep in the quantum regime. Fully incorporating both thermal and quantum effects, the current generated in the model can be used to detect the onset of "genuine quantumness" in the form of quantum contextuality. The model can also be used to generate steady-state entanglement in the presence of arbitrarily hot environment.