Minimal model of a heat engine: Information theory approach

Zhou, Yun; Segal, Dvira

doi:10.1103/physreve.82.011120

Cited by 52 publications

(58 citation statements)

References 14 publications

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“…Comparing the equations for heat transfer between the system and the reservoirs, Eqs. (8) and (10), the quantity of heat 8J(p ′ 1 − p 1 ) appears in both the equations. Obviously, this term is absent in the uncoupled case for which J = 0.…”

Section: A the Heat Cyclementioning

confidence: 99%

“…Many models have served to investigate the validity of second law of thermodynamics in the quantum regime [8,9]. The possibility of small scale devices and information processing machines [10] has generated further interest into the fundamental limits imposed on the heat generation, cooling power and thermal efficiencies achievable with these models [11][12][13]. Quantum analogues of Carnot cycles, Otto cycles and other brownian machines have been analysed [14,15].…”

Section: Introductionmentioning

confidence: 99%

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Coupled quantum Otto cycle

2011

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We study the 1-d isotropic Heisenberg model of two spin-1/2 systems as a quantum heat engine. The engine undergoes a four-step Otto cycle where the two adiabatic branches involve changing the external magnetic field at a fixed value of the coupling constant. We find conditions for the engine efficiency to be higher than the uncoupled model; in particular, we find an upper bound which is tighter than the Carnot bound. A new domain of parameter values is pointed out which was not feasible in the interaction-free model. Locally, each spin seems to effect the flow of heat in a direction opposite to the global temperature gradient. This seeming contradiction to the second law can be resolved in terms of local effective temperature of the spins.

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Section: A the Heat Cyclementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Coupled quantum Otto cycle

2011

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“…In both cases, a modulator (piston) can take work and gain energy from the system (be coherently-amplified) in a closed cycle. This work originates neither from the probe free-energy [10,11] nor from the heat energy of the bath (as in Szilard's engine [1][2][3][4][5][6][7][8]) but from a hitherto unexploited (and little-discussed) source: the inevitable change of the system-bath (S-B) correlation (interaction) energy (see [29]) by a brief QND measurement [16][17][18][19][20][21]. Only non-Markovian supersystem (S+B) dynamics can yield extractable work following such a measurement, as opposed to its Markovian limit that ignores system-bath correlations (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…(25) under a cyclic unitary evolution of the total Hamiltonian, starting from equilibrium of the supersystem and the probe, can be proved completely generally. It shows that the second law that forbids drawing work from a single bath only applies to the entangled evolution of S+B+P and that their standard separability assumption [1][2][3][4][5][6][7][8] fails for sufficiently fast cycles.…”

Section: Consistency With the Second Lawmentioning

confidence: 99%

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Work extraction via quantum nondemolition measurements of qubits in cavities: Non-Markovian effects

et al. 2013

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We show that frequent nondemolition measurements of a quantum system immersed in a thermal bath allow the extraction of work in a closed cycle from the system-bath interaction (correlation) energy, a hitherto unexploited work resource. It allows for work even if no information is gathered or the bath is at zero temperature, provided the cycle is within the bath memory time. The predicted work resource may be the basis of quantum engines embedded in a bath with long memory time, such as the electromagnetic bath of a high-Q cavity coupled to two-level systems. I. IntroductionInformation acquired by an observer on the system can be commuted into work in a single-bath engine [1][2][3][4][5][6][7][8][9]. To this end, the observer ("Maxwell's demon") must manipulate the system according to the results of measurements performed on it. The measurements have therefore to be selective, i.e., their outcomes must be read and discriminated to determine the observer's course of action [7,10]. The balance of work and information is embodied by the Szilard-Landauer (SL) principle [1, 2] whereby work obtainable from a measurement must not exceed the energy cost of erasing its record from the observer's memory. Notwithstanding ongoing efforts to expand information-based thermodynamics (IT) so as to include measurement-cost effects [10][11][12] beyond the original SL balance (see Appendix), an important aspect has been little addressed thus far [13]: How essential is the thermodynamic paradigm of system-bath separability [14,15] to the analysis of work extraction by measurements?This question is here investigated in the context of non-Markovian quantum thermodynamics "under observation" [16][17][18][19][20][21]. Namely, we show that frequent measurements can induce changes in system-bath correlations, unaccounted for by the separability paradigm, and thereby change the tradeoff of information and work. Consequently, selective (read) measurements can extract more work in a closed cycle than what the SL principle allows. This effect requires the cycle to be completed within a non-Markovian (bath-memory) time-scale.We further show that non-selective quantum nondemolition (QND) measurements of the system energy (which we shall also denote as unread measurements, i.e., measurements whose outcomes do not matter) enable the system to do work in a cycle, although they provide no information on the system, nor do they change its state (by their definition as QND measurements) and thus do not act as a "demon." Work is shown to be obtainable within the bath memory time even at zero temperature (T = 0),

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Introduction to Quantum Thermodynamics: History and Prospects

Alicki

Kosloff

2018

Fundamental Theories of Physics

110

122

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Quantum Thermodynamics is a continuous dialogue between two independent theories: Thermodynamics and Quantum Mechanics. Whenever the two theories have addressed the same phenomena new insight has emerged. We follow the dialogue from equilibrium Quantum Thermodynamics and the notion of entropy and entropy inequalities which are the base of the II-law. Dynamical considerations lead to nonequilibrium thermodynamics of quantum Open Systems. The central part played by completely positive maps is discussed leading to the Gorini-Kossakowski-Lindblad-Sudarshan "GKLS" equation. We address the connection to thermodynamics through the system-bath weak-coupling-limit WCL leading to dynamical versions of the I-law. The dialogue has developed through the analysis of quantum engines and refrigerators. Reciprocating and continuous engines are discussed. The autonomous quantum absorption refrigerator is employed to illustrate the III-law. Finally, we describe some open questions and perspectives. arXiv:1801.08314v2 [quant-ph] 31 May 2018

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Minimal model of a heat engine: Information theory approach

Cited by 52 publications

References 14 publications

Coupled quantum Otto cycle

Coupled quantum Otto cycle

Work extraction via quantum nondemolition measurements of qubits in cavities: Non-Markovian effects

Introduction to Quantum Thermodynamics: History and Prospects

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