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A heat engine is a machine which uses the temperature difference between a hot and a cold reservoir to extract work. Here both reservoirs are quantum systems and a heat engine is described by a unitary transformation which decreases the…

Quantum Physics · Physics 2009-11-11 Dominik Janzing

A way to address the conundrum of Quantum Gravity is to illustrate the potentially fundamental interplay between quantum field theory, curved space-times physics and thermodynamics. So far, when studying moving quantum systems in the…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Nathaniel Obadia

Quantum many-body systems serve as a suitable working medium for realizing quantum thermal machines (QTMs) by offering distinct advantages such as cooperative many-body effects, and performance boost at the quantum critical points. However,…

Quantum Physics · Physics 2024-05-01 Saikat Sur , Pritam Chattopadhyay , Madhuparna Karmakar , Avijit Misra

We show that coupled autonomous thermal machines, in the presence of three heat reservoirs and following a global linear-irreversible description, provide a unified framework to accommodate the variety of expressions for the efficiency at…

Statistical Mechanics · Physics 2023-08-15 Ramandeep S. Johal , Renuka Rai

We analyze the efficiency of thermal engines (either quantum or classical) working with a single heat reservoir like atmosphere. The engine first gets an energy intake, which can be done in arbitrary non-equilibrium way e.g. combustion of…

Statistical Mechanics · Physics 2015-03-20 Pankaj Mehta , Anatoli Polkovnikov

The efficiency of any heat engine, defined as the ratio of average work output to heat input, is bounded by Carnot's celebrated result. However, this measure is insufficient to characterize the properties of miniaturized heat engines…

We propose an operational definition for the local temperature of a quantum field employing Unruh-DeWitt detectors, as used in the study of the Unruh and Hawking effects. With this definition, an inhomogeneous quantum system in equilibrium…

Quantum Physics · Physics 2017-04-03 Sandra Robles , Javier Rodriguez-Laguna

We demonstrate a genuine quantum feature of heat: the power emitted by a qubit (quantum two-level system) into a reservoir under continuous driving shows peaks as a function of frequency $f$. These resonant features appear due to the…

Quantum Physics · Physics 2023-05-24 George Thomas , Jukka P. Pekola

We introduce a simple two-level heat engine to study the efficiency in the condition of the maximum power output, depending on the energy levels from which the net work is extracted. In contrast to the quasi-statically operated Carnot…

Statistical Mechanics · Physics 2016-12-05 Sang Hoon Lee , Jaegon Um , Hyunggyu Park

In this paper, heat and Carnot's working substance are defined respectively by the equations $E=3pV$ and $E=3/2pV$, relating the energy $E$, the pressure $p$ and the volume $V$ of these two corpuscular systems. The thermodynamic-kinetic…

Chemical Physics · Physics 2019-10-08 Claudio Zamitti Mammana

Enhancing the efficiency of quantum heat engines (QHEs) is crucial for advancing fundamental research and quantum technology.We here we explore a quantum Stirling cycle using a twoqubit quantum Rabi model with spin-spin coupling as a…

Quantum Physics · Physics 2024-10-08 Luxin Xu , Chunfeng Wu , Changliang Ren

We discuss the efficiency of a heat engine operating in a nonequilibrium steady state maintained by two heat reservoirs. Within the general framework of linear irreversible thermodynamics we derive a universal upper bound on the efficiency…

Statistical Mechanics · Physics 2016-05-18 Artem Ryabov , Viktor Holubec

We present a mechanism for efficiency increase in quantum heat engines containing internal energy levels that do not couple to the external work sink. The gain is achieved by using these levels to channel heat in a direction opposite to the…

Quantum Physics · Physics 2022-01-25 Thiago R. de Oliveira , Daniel Jonathan

We investigate the interplay between quantum thermodynamics, quantum correlations, and quantum coherence within the framework of the Unruh-DeWitt (UdW) detector model. By analyzing both the steady and dynamical states of various quantum…

Quantum Physics · Physics 2025-12-23 Omar Bachain , Mohamed Amazioug , Rachid Ahl Laamara

Heating under periodic driving is a generic nonequilibrium phenomenon, and it is a challenging problem in nonequilibrium statistical physics to derive a quantitatively accurate heating rate. In this work, we provide a simple formula on the…

Statistical Mechanics · Physics 2022-02-16 Takashi Mori

Quantum thermal machines make use of non-classical thermodynamic resources, one of which is interactions between elements of the quantum working medium. In this paper, we examine the performance of a quasi-static quantum Otto engine based…

Quantum Physics · Physics 2022-01-03 Venu Mehta , Ramandeep S. Johal

We study an Otto heat machine whose working substance is a single two-level system interacting with a cold thermal reservoir and with a squeezed hot thermal reservoir. By adjusting the squeezing or the adiabaticity parameter (the…

We present quantum heat machines using a diatomic molecule modelled by a $q$-deformed potential as a working medium. We analyze the effect of the deformation parameter and other potential parameters on the work output and efficiency of the…

Quantum Physics · Physics 2026-01-06 C. O. Edet , E. P. Inyang , O. Abah , N. Ali

Considering ideal paramagnetic medium, in this paper we deduced an expression for the thermal efficiency of Carnot heat engine with a paramagnetic gas as working substance. We found that the efficiency depends on the limits of maximum and…

Statistical Mechanics · Physics 2019-05-17 Manuel Malaver

Abstract We perform an experiment in which a quantum heat engine works under two reservoirs, one at a positive spin temperature and the other at an effective negative spin temperature i.e., when the spin system presents population…