Efficiently Fuelling a Quantum Engine with Incompatible Measurements

TL;DR

This paper introduces a quantum measurement engine that uses simultaneous incompatible measurements of position and momentum to extract work, demonstrating protocols with high efficiency and analyzing the work distribution.

Contribution

It presents novel protocols for quantum work extraction using incompatible measurements, including single-shot and continuous measurement schemes, with exact work distribution results.

Findings

Both protocols can achieve unit work conversion efficiency.

Measurement noise directly relates to the amount of extractable work.

Exact work distribution formulas are derived for arbitrary times.

Abstract

We propose a quantum harmonic oscillator measurement engine fueled by simultaneous quantum measurements of the non-commuting position and momentum quadratures of the quantum oscillator. The engine extracts work by moving the harmonic trap suddenly, conditioned on the measurement outcomes. We present two protocols for work extraction, respectively based on single-shot and time-continuous quantum measurements. In the single-shot limit, the oscillator is measured in a coherent state basis; the measurement adds an average of one quantum of energy to the oscillator, which is then extracted in the feedback step. In the time-continuous limit, continuous weak quantum measurements of both position and momentum of the quantum oscillator result in a coherent state, whose coordinates diffuse in time. We relate the extractable work to the noise added by quadrature measurements, and present exact results for the work distribution at arbitrary finite time. Both protocols can achieve unit work conversion efficiency in principle.