Strongly Coupled Quantum Heat Machines

We study a quantum heat engine at strong coupling between the system and the thermal reservoirs. Exploiting a collective coordinate mapping, we incorporate system-reservoir correlations into a consistent thermodynamic analysis, thus circumventing the usual restriction to weak coupling and vanishing correlations. We apply our formalism to the example of a quantum Otto cycle, demonstrating that the performance of the engine is diminished in the strong coupling regime with respect to its weakly coupled counterpart, producing a reduced net work output and operating at a lower energy conversion efficiency. We identify costs imposed by sudden decoupling of the system and reservoirs around the cycle as being primarily responsible for the diminished performance, and define an alternative operational procedure which can partially recover the work output and efficiency. More generally, the collective coordinate mapping holds considerable promise for wider studies of thermodynamic systems beyond weak reservoir coupling.

show abstract

“…The average energy at any point along the stroke, given by equation (40), may then be calculated in this new basis:…”

Section: Isentropic Expansionmentioning

confidence: 99%

Performance of a quantum heat engine at strong reservoir coupling

2017

View full text Add to dashboard Cite

show abstract

“…Non-Markovian bath dynamics is, in general, very complicated and strongly depend on the specific bath realization. Heat machines and the second law in the presence of strong coupling have been discussed in [70][71][72].…”

Section: The Heat Exchanger and The Bathsmentioning

confidence: 99%

Quantum Heat Machines Equivalence, Work Extraction beyond Markovianity, and Strong Coupling via Heat Exchangers

Uzdin

Levy

Kosloff

2016

Entropy

View full text Add to dashboard Cite

Various engine types are thermodynamically equivalent in the quantum limit of small "engine action". Our previous derivation of the equivalence is restricted to Markovian heat baths and to implicit classical work repository (e.g., laser light in the semi-classical approximation). In this paper, all the components, baths, batteries, and engines, are explicitly taken into account. To neatly treat non-Markovian dynamics, we use mediating particles that function as a heat exchanger. We find that, on top of the previously observed equivalence, there is a higher degree of equivalence that cannot be achieved in the Markovian regime. Next, we focus on the quality of the battery charging process. A condition for positive energy increase and zero entropy increase (work) is given. Moreover, it is shown that, in the strong coupling regime, it is possible to super-charge a battery. With super-charging, the energy of the battery is increased while its entropy is being reduced at the same time.

show abstract

“…As a result, both the actual time-evolution and the subsequent stationary state might differ significantly from the ones predicted by the LGKS quantum master equation. A rigorous treatment of such problem requires more sophisticated tools, like higher order perturbative quantum master equations [45,46], non-Markovian stochastic Schrödinger equations [47][48][49], hierarchical Heisenberg equations [50,51], or other non-perturbative methods [52][53][54].…”

Section: Suppression Of Internal Dissipation and Heat Leaksmentioning

confidence: 99%

Internal dissipation and heat leaks in quantum thermodynamic cycles

2015

View full text Add to dashboard Cite

The direction of the steady-state heat currents across a generic quantum system connected to multiple baths may be engineered so as to realize virtually any thermodynamic cycle. In spite of their versatility such continuous energy-conversion systems are generally unable to operate at maximum efficiency due to non-negligible sources of irreversible entropy production. In this paper we introduce a minimal model of irreversible absorption chiller. We identify and characterize the different mechanisms responsible for its irreversibility, namely heat leaks and internal dissipation, and gauge their relative impact in the overall cooling performance. We also propose reservoir engineering techniques to minimize these detrimental effects. Finally, by looking into a known three-qubit embodiment of the absorption cooling cycle, we illustrate how our simple model may help to pinpoint the different sources of irreversibility naturally arising in more complex practical heat devices.

show abstract

Strongly Coupled Quantum Heat Machines

Cited by 100 publications

References 63 publications

Performance of a quantum heat engine at strong reservoir coupling

Performance of a quantum heat engine at strong reservoir coupling

Quantum Heat Machines Equivalence, Work Extraction beyond Markovianity, and Strong Coupling via Heat Exchangers

Internal dissipation and heat leaks in quantum thermodynamic cycles

Contact Info

Product

Resources

About