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The concept of thermal machines has evolved from the canonical steam engine to the recently proposed nanoscopic quantum systems as working fluids. The latter obey quantum open system dynamics and frequently operate in non-equilibrium…

We investigate and ascertain the ideal inputs to any finite-time thermodynamic process. We demonstrate that the expectation values of entropy flow, heat, and work can all be determined via Hermitian observables of the initial state. These…

Quantum Physics · Physics 2023-05-02 Paul M. Riechers , Chaitanya Gupta , Artemy Kolchinsky , Mile Gu

The context of the present paper is stochastic thermodynamics - an approach to nonequilibrium thermodynamics rooted within the broader framework of stochastic control. In contrast to the classical paradigm of Carnot engines, we herein…

Systems and Control · Electrical Eng. & Systems 2021-01-08 Rui Fu , Olga Movilla Miangolarra , Amirhossein Taghvaei , Yongxin Chen , Tryphon T. Georgiou

We introduce the resource-theoretic free energy of a quantum channel as the maximal work extractable from the channel as its output equilibrates to a thermal state and its reference system remains locally intact. It is proportional to the…

Quantum Physics · Physics 2025-10-29 Himanshu Badhani , Dhanuja G S , Siddhartha Das

Established heat engines in quantum regime can be modeled with various quantum systems as working substances. For example, in the non-relativistic case, we can model the heat engine using infinite potential well as a working substance to…

Quantum Physics · Physics 2020-06-09 Pritam Chattopadhyay , Goutam Paul

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…

Quantum Physics · Physics 2014-02-03 Johannes Roßnagel , Obinna Abah , Ferdinand Schmidt-Kaler , Kilian Singer , Eric Lutz

This paper considers work extraction from a quantum system to a work storage system (or weight) following reference [1]. An alternative approach is here developed that relies on the comparison of subspace dimensions without a need to…

Quantum Physics · Physics 2016-04-07 J. Gemmer , J. Anders

We consider irreversible and coupled reversible-irreversible nonlinear port-Hamiltonian systems and the respective sets of thermodynamic equilibria. In particular, we are concerned with optimal state transitions and output stabilization on…

Optimization and Control · Mathematics 2024-10-08 Friedrich Philipp , Manuel Schaller , Karl Worthmann , Timm Faulwasser , Bernhard Maschke

We study the work fluctuations in ergotropic heat engines, namely two-strokes quantum Otto engines where the work stroke is designed to extract the ergotropy (the maximum amount of work by a cyclic unitary evolution) from a couple of…

Quantum Physics · Physics 2023-11-10 Giovanni Chesi , Chiara Macchiavello , Massimiliano Federico Sacchi

We revisit the problem of work extraction from a system in contact with a heat bath to a work storage system, and the reverse problem of state formation from a thermal system state in single-shot quantum thermodynamics. A physically…

Quantum Physics · Physics 2017-12-18 Shang-Yung Wang

Evaluating the maximum amount of work extractable from a nanoscale quantum system is one of the central problems in quantum thermodynamics. Previous works identified the free energy of the input state as the optimal rate of extractable work…

Quantum Physics · Physics 2026-03-06 Kaito Watanabe , Ryuji Takagi

Quantum thermal machines offer promising platforms for exploring the fundamental limits of thermodynamics at the microscopic scale. The previous study demonstrated that the incorporation of a catalyst can significantly enhance the…

Quantum Physics · Physics 2026-02-17 Cong Fu , Ousi Pan , Zhiqiang Fan , Yushun Tang , Shanhe Su , Youhui Lin , Jincan Chen

How much work can be extracted from a heat bath using a thermal machine? The study of this question has a very long tradition in statistical physics in the weak-coupling limit, applied to macroscopic systems. However, the assumption that…

Quantum Physics · Physics 2015-06-17 R. Gallego , A. Riera , J. Eisert

The widely debated feasibility of thermodynamic machines achieving Carnot efficiency at finite power has been convincingly dismissed. Yet, the common wisdom that efficiency can only be optimal in the limit of infinitely-slow processes…

Statistical Mechanics · Physics 2017-07-28 Matteo Polettini , Massimiliano Esposito

For a four-stroke asymmetrically driven quantum Otto engine with working medium modeled by a single qubit, we study the bounds on non-equilibrium fluctuations of work and heat. We find strict relations between the fluctuations of work and…

Statistical Mechanics · Physics 2023-08-02 Sandipan Mohanta , Madhumita Saha , B. Prasanna Venkatesh , Bijay Kumar Agarwalla

We study coupled quantum systems as the working media of thermodynamic machines. Under a suitable phase-space transformation, the coupled systems can be expressed as a composition of independent subsystems. We find that for the coupled…

Quantum Physics · Physics 2017-09-12 George Thomas , Manik Banik , Sibasish Ghosh

We derive an analytical expression for maximum efficiency at fixed power of heat pumps operating along a finite-time reverse Carnot cycle under the low-dissipation assumption. The result is cumbersome, but it implies simple formulas for…

Statistical Mechanics · Physics 2022-02-28 Zhuolin Ye , Viktor Holubec

The construction of efficient thermal engines operating at finite times constitutes a fundamental and timely topic in nonequilibrium thermodynamics. We introduce a strategy for optimizing the performance of Brownian engines, based on a…

Statistical Mechanics · Physics 2021-08-04 C. E. Fernández Noa , Angel L. L. Stable , William G. C. Oropesa , Alexandre Rosas , C. E. Fiore

The spin-boson model, often used in NMR and ESR physics, quantum optics and spintronics, is considered in a solvable limit to model a spin one-half particle interacting with a bosonic thermal bath. By applying external pulses to a…

Statistical Mechanics · Physics 2009-11-07 A. E. Allahverdyan , Th. M. Nieuwenhuizen

Recent theoretical and experimental studies in quantum heat engines show that, in the quasi-static regime, it is possible to have higher efficiency than the limit imposed by Carnot, provided that engineered reservoirs are used. The…

Quantum Physics · Physics 2021-05-26 Rogério J. de Assis , J. S. Sales , Udson C. Mendes , Norton G. de Almeida