Controlling quantum flux through measurement: an idealised example

TL;DR

This paper demonstrates how measurement strength in a quantum system can be used to induce and control particle flux in a symmetric double quantum dot, highlighting the impact of measurement disturbance on quantum transport.

Contribution

It introduces a simple idealised quantum model showing how weak measurements can generate and control flux, revealing the role of measurement disturbance in quantum transport.

Findings

Measurement strength controls particle flux in a symmetric quantum dot.

Weak measurements can induce transport without system asymmetry.

Measurement disturbance affects quantum system evolution and transport control.

Abstract

Classically, no transfer occurs between two equally filled reservoirs no matter how one looks at them, but the situation can be different quantum mechanically. This paradoxically surprising phenomenon rests on the distinctive property of the quantum world that one cannot stare at a system without disturbing it. It was recently discovered that this seemingly annoying feature could be harnessed to control small quantum systems using weak measurements. Here we present one of the simplest models -- an idealised double quantum dot -- where by toying with the dot measurement strength, i.e. the intensity of the look, it is possible to create a particle flux in an otherwise completely symmetric system. The basic property underlying this phenomena is that measurement disturbances are very different on a system evolving unitarily and a system evolving dissipatively. This effect shows that adaptive measurements can have dramatic effects enabling transport control but possibly inducing biases in the measurement of macroscopic quantities if not handled with care.