A nano heat engine beyond the Carnot limit

TL;DR

This paper demonstrates that a quantum Otto heat engine using a squeezed thermal reservoir can surpass the classical Carnot efficiency limit, with potential experimental implementation using trapped ions.

Contribution

It introduces a quantum Otto cycle with a squeezed reservoir, showing efficiency beyond Carnot limit and proposing a feasible experimental setup.

Findings

Efficiency at maximum power increases exponentially with squeezing parameter r.

Efficiency can approach unity for large squeezing, exceeding classical limits.

Monte Carlo simulations support the feasibility of the proposed experimental scheme.

Abstract

Heat engines extract work by running cyclically between two heat reservoirs. When the two reservoirs are thermal and at different temperatures, the maximum efficiency of the engine is given by the Carnot limit. Here we consider a quantum Otto cycle for a time-dependent harmonic oscillator coupled to an engineered squeezed thermal reservoir. We show that the efficiency at maximum power increases with the degree of squeezing, exponentially approaching unity for large squeezing parameters $r$. Furthermore, we propose an experimental scheme to implement such a system by using a single trapped ion in a linear Paul trap with special geometry and coupled to engineered reservoirs. Our analytical investigations are supported with Monte Carlo simulations that demonstrate the feasibility of our proposal. For realistic trap parameters, an increase of up to a factor of four is reached, largely exceeding the classical limit.