Introduction to Quantum Thermodynamics: History and Prospects

Alicki, Robert; Kosloff, Ronnie

doi:10.1007/978-3-319-99046-0_1

Cited by 107 publications

(129 citation statements)

References 187 publications

(194 reference statements)

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“…The adiabatic parameter can be large, indicating fast driving relative to the Bohr frequencies, while varying slowly. The resulting master equation is consistent with the thermodynamic laws [41,48].…”

Section: Dynamics Of the Carnot-analog Cyclesupporting

confidence: 69%

Quantum signatures in the quantum Carnot cycle

Dann

Kosloff

2020

New J. Phys.

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The Carnot cycle combines reversible isothermal and adiabatic strokes to obtain optimal efficiency, at the expense of a vanishing power output. Quantum Carnot-analog cycles are constructed and solved, operating irreversibly with positive power. Swift thermalization is obtained in the isotherms utilizing shortcut to equilibrium protocols and the adiabats employ frictionless unitary shortcuts. The working medium in this study is composed of a particle in a driven harmonic trap. For this system, we solve the dynamics employing a generalized canonical state. Such a description incorporates both changes in energy and coherence. This allows comparing three types of Carnot-analog cycles, Carnot-shortcut, Endo-shortcut and Endo-global. The Carnot-shortcut engine demonstrates the trade-off between power and efficiency. It posses a maximum in power, a minimum cycle-time where it becomes a dissipator and for a diverging cycle-time approaches the ideal Carnot efficiency. The irreversibility of the cycle arises from non-adiabatic driving, which generates coherence. To study the role of coherence we compare the performance of the shortcut cycles, where coherence is limited to the interior of the strokes, with the Endo-global cycle where the coherence never vanishes. The Endo-global engine exhibits a quantum signature at a short cycle-time, manifested by a positive power output while the shortcut cycles become dissipators. If energy is monitored the back action of the measurement causes dephasing and the power terminates.CA c h [4,5], which has been generalized for weak dissipation [6,7].In the quantum regime energy transfer is constrained as well by the second law of thermodynamics [8][9][10][11]. Implying that quantum heat engines are also bounded by the Carnot efficiency. Reversibility and optimal efficiency is obtained in the quantum adiabatic limit, requiring an infinite cycle-time τ cycle .

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Section: Dynamics Of the Carnot-analog Cyclesupporting

confidence: 69%

Quantum signatures in the quantum Carnot cycle

Dann

Kosloff

2020

New J. Phys.

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“…The setup we consider consists of a two-level quantum system S with energy gap ò(t) that can be externally modulated 4 . As schematically shown in figure 1(a), the system is placed in thermal contact with two reservoirs, the hot bath H at inverse temperature β H and the cold bath C at inverse temperature β C , respectively characterized by coupling constants λ H (t) and λ C (t) that can be modulated in time.…”

Section: Maximum Powermentioning

confidence: 99%

“…The fundamental limitations to the inter-conversion of heat into work stem from the concept of irreversibility and are at the core of the second law of thermodynamics. A working medium in contact with two baths at different temperatures is also significant from a practical point of view, since it is the paradigm behind the following specific machines: the heat engine, the refrigerator [1][2][3][4], the thermal accelerator [5], and the heater [5].…”

Section: Introductionmentioning

confidence: 99%

Maximum power and corresponding efficiency for two-level heat engines and refrigerators: optimality of fast cycles

et al. 2019

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We study how to achieve the ultimate power in the simplest, yet non-trivial, model of a thermal machine, namely a two-level quantum system coupled to two thermal baths. Without making any prior assumption on the protocol, via optimal control we show that, regardless of the microscopic details and of the operating mode of the thermal machine, the maximum power is universally achieved by a fast Otto-cycle like structure in which the controls are rapidly switched between two extremal values. A closed formula for the maximum power is derived, and finite-speed effects are discussed. We also analyze the associated efficiency at maximum power showing that, contrary to universal results derived in the slow-driving regime, it can approach Carnot's efficiency, no other universal bounds being allowed.'fast-driving' regime, i.e. when the driving frequency is faster than the typical dissipation rate induced by the baths, which has received little attention in literature [50][51][52].By applying our optimal protocol to heat engines and refrigerators, we find new theoretical bounds on the efficiency at maximum power (EMP). Many upper limits to the EMP, strictly smaller than Carnot's efficiency, have been derived in literature, such as the Curzon-Ahlborn and Schmiedl-Seifert efficiencies. The Curzon-Ahlborn efficiency emerges in various specific models [53][54][55], and it has been derived by general arguments from linear irreversible thermodynamics [56]. The Schmiedl-Seifert efficiency has been proven to be universal in cyclic Brownian heat engines [57] and for any driven system operating in the slow-driving regime [24]. By studying the efficiency of our system at the ultimate power, i.e. in the fast-driving regime, we prove that there is no fundamental upper bound to the EMP. Indeed, we show that the Carnot efficiency is reachable at maximum power through a suitable engineering of the bath couplings. This is our second main results, illustrated in figures 2(b), (c) and figure 3. In view of experimental implementations, we assess the impact of finite-time effects on our optimal protocol, finding that the maximum power does not decrease much if the external driving is not much slower than the typical dissipation rate induced by the baths [58,59]. Furthermore, we apply our optimal protocol to two experimentally accessible models, namely photonic baths coupled to a qubit [22, 60-63] and electronic leads coupled to a quantum dot [21,23,58,59,64,65].C , and Γ in (c) denotes *  G( ) H . 4 In principle, one can consider a broader family of controls including the possibility of rotating the Hamiltonian eigenvectors; however there is evidence that such an additional freedom does not help in two-level systems [45, 46]. ≔ [ ] ( ) J J t p t J J t p t

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“…Specifically it works as follows (see figure 2). The lower polariton frequency plays the role of the volume of the working fluid (similar to other single oscillator engines [1,2]) and it can be controlled via the laser detuning. This is the central tool used to operate the engine through the four strokes of the cycle.…”

Section: The Polariton-based Optomechanical Heat Enginementioning

confidence: 99%

“…A quantum heat engine uses a quantum system as working fluid. The practical realization of these devices is interesting as platforms for the experimental investigation of the thermodynamics of the quantum world and of non-equilibrium systems [1,2].…”

Section: Introductionmentioning

confidence: 99%

An optomechanical heat engine with feedback-controlled in-loop light

et al. 2019

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The dissipative properties of an optical cavity can be effectively controlled by placing it in a feedback loop where the light at the cavity output is detected and the corresponding signal is used to modulate the amplitude of a laser field which drives the cavity itself. Here we show that this effect can be exploited to improve the performance of an optomechanical heat engine which makes use of polariton excitations as working fluid. In particular we demonstrate that, by employing a positive feedback close to the instability threshold, it is possible to operate this engine also under parameters regimes which are not usable without feedback, and which may significantly ease the practical implementation of this device.

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Introduction to Quantum Thermodynamics: History and Prospects

Cited by 107 publications

References 187 publications

Quantum signatures in the quantum Carnot cycle

Quantum signatures in the quantum Carnot cycle

Maximum power and corresponding efficiency for two-level heat engines and refrigerators: optimality of fast cycles

An optomechanical heat engine with feedback-controlled in-loop light

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