Speed and efficiency limits of multilevel incoherent heat engines

Mukherjee, Victor; Niedenzu, Wolfgang; Kofman, A. G.; Kurizki, Gershon

doi:10.1103/physreve.94.062109

Cited by 23 publications

(21 citation statements)

References 55 publications

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“…Thus, if one starts from a high w k ( w > k *) and progressively lowers its value, a transition from QR to QHE occurs at w k *, followed by a transition to the accelerator regime. On a related note, the above QHE-QR transition has also been shown in four-stroke [61] and continuous thermal machines [50,54,62]. Note that, while Q h and Q c reverse their sign only at the first transition (QR-QHE), W undergoes sign reversal at the QHE-accelerator transition as well.…”

Section: Thermalization Stroke ( T )mentioning

confidence: 54%

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Quantum magnetometry using two-stroke thermal machines

et al. 2020

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The precise estimation of small parameters is a challenging problem in quantum metrology. Here, we introduce a protocol for accurately measuring weak magnetic fields using a two-level magnetometer, which is coupled to two (hot and cold) thermal baths and operated as a two-stroke quantum thermal machine. Its working substance consists of a two-level system (TLS), generated by an unknown weak magnetic field acting on a qubit, and a second TLS arising due to the application of a known strong and tunable field on another qubit. Depending on this field, the machine may either act as an engine or a refrigerator. Under feasible conditions, determining this transition point allows to reduce the relative error of the measurement of the weak unknown magnetic field by the ratio of the temperatures of the colder bath to the hotter bath.

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Section: Thermalization Stroke ( T )mentioning

confidence: 54%

“…Depending on the sign of Q h , Q c and W, TTMs may depict four distinct regimes of operation [53,54],…”

Section: Thermalization Stroke ( T )mentioning

confidence: 99%

Quantum magnetometry using two-stroke thermal machines

et al. 2020

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“…To obtain the efficiency bound, we need to extract the ergotropy from the WF (by the piston via a suitable unitary transformation) before its interaction with the cold bath. In continuous cycles where both baths are simultaneously coupled to the WF [19,26,63], part of the ergotropy may then be dissipated into the cold bath, so that such cycles are inherently less efficient than stroke cycles. For time-dependent Hamiltonians, the requirement that H(t) commutes with itself at all times, e.g., a HO with time-independent eigenstates, will be adopted in this chapter for any interaction of a system with a bath, since Hamiltonians that do not commute with themselves at different times reduce the efficiency via "quantum friction" [20,64].…”

Section: Efficiency Bound Of Cyclic Quantum Engines Powered By Thmentioning

confidence: 99%

Thermodynamic Principles and Implementations of Quantum Machines

Ghosh

Niedenzu

Mukherjee

et al. 2018

Fundamental Theories of Physics

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The efficiency of cyclic heat engines is limited by the Carnot bound. This bound follows from the second law of thermodynamics and is attained by engines that operate between two thermal baths under the reversibility condition whereby the total entropy does not increase. By contrast, the efficiency of engines powered by quantum non-thermal baths has been claimed to surpass the thermodynamic Carnot bound. The key to understanding the performance of such engines is a proper division of the energy supplied by the bath to the system into heat and work, depending on the associated change in the system entropy and ergotropy. Due to their hybrid character, the efficiency bound for quantum engines powered by a non-thermal bath does not solely follow from the laws of thermodynamics. Hence, the thermodynamic Carnot bound is inapplicable to such hybrid engines. Yet, they do not violate the principles of thermodynamics.An alternative means of boosting machine performance is the concept of heat-to-work conversion catalysis by quantum non-linear (squeezed) pumping of the piston mode. This enhancement is due to the increased ability of the squeezed piston to store ergotropy. Since the catalyzed machine is fueled by thermal baths, it adheres to the Carnot bound.We conclude by arguing that it is not quantumness per se that improves the machine performance, but rather the properties of the baths, the working fluid and the piston that boost the ergotropy and minimize the wasted heat in both the input and the output. CONTENTS VI. Catalysis of heat-to-work conversion in quantum machines13 Model of catalyzed quantum heat engine 13 Model analysis: Derivation of the Lindblad master equation 14 Work extraction under non-linear pumping 15 Efficiency boost 16 VII. Discussion: quantumness and engine performance 17 References 17 *

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“…These quantum processes with a finite time duration can be also interesting as a non-adiabatic counterpart to a local quench dynamics of a suddenly cut and stitched spin chains [15], and for bond impurity chain cutting [16]. Another related field is the quantum thermodynamics [17], or the physics of quantum heat machines [18][19][20][21], where one part of the spin chain can be considered as a working medium, connected to and disconnected from the other part, which plays the role of a thermal reservoir.…”

Section: Introductionmentioning

confidence: 99%

High-fidelity non-adiabatic cutting and stitching of a spin chain via local control

et al. 2018

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We propose and analyze, focusing on non-adiabatic effects, a technique of manipulating quantum spin systems based on local 'cutting' and 'stitching' of the Heisenberg exchange coupling between the spins. This first operation is cutting of a bond separating a single spin from a linear chain, or of two neighboring bonds for a ring-shaped array of spins. We show that the disconnected spin can be in the ground state with a high-fidelity even after a non-adiabatic process. Next, we consider inverse operation of stitching these bonds to increase the system size. We show that the optimal control algorithm can be found by using common numerical procedures with a simple twoparametric control function able to produce a high-fidelity cutting and stitching. These results can be applied for manipulating ensembles of quantum dots, considered as prospective elements for quantum information technologies, and for design of machines based on quantum thermodynamics.

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Speed and efficiency limits of multilevel incoherent heat engines

Cited by 23 publications

References 55 publications

Quantum magnetometry using two-stroke thermal machines

Quantum magnetometry using two-stroke thermal machines

Thermodynamic Principles and Implementations of Quantum Machines

High-fidelity non-adiabatic cutting and stitching of a spin chain via local control

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