Multiatom Quantum Coherences in Micromasers as Fuel for Thermal and Nonthermal Machines

TL;DR

This paper investigates how the quantum state preparation of multiatom clusters influences the performance and type of quantum thermal machines, classifying their coherences as fuel for different machine functionalities.

Contribution

It introduces a classification of multiatom quantum coherences based on their ability to fuel nonthermal or thermal quantum machines, with proposed experimental implementations.

Findings

Identifies multiatom states suitable as fuel for nonthermal machines.

Classifies atomic coherences according to their thermodynamic role.

Proposes experimental schemes for preparing promising multiatom states.

Abstract

In this paper we address the question: To what extent is the quantum state preparation of multiatom clusters (before they are injected into the microwave cavity) instrumental for determining not only the kind of machine we may operate but also the quantitative bounds of its performance? Figuratively speaking, if the multiatom cluster is the "crude oil", the question is: Which preparation of the cluster is the refining process that can deliver a "gasoline" with a "specific octane"? We classify coherences or quantum correlations among the atoms according to their ability to serve as (i) fuel for nonthermal machines corresponding to atomic states whose coherences displace or squeeze the cavity field, as well as cause its heating; and (ii) fuel which is purely "combustible", i.e., corresponds to atomic states that only allow for heat and entropy exchange with the field and can energize a proper heat engine. We identify highly promising multiatom states for each kind of fuel and propose viable experimental schemes for their implementation.