Relaxation due to random collisions with a many-qudit environment

Gennaro, Giuseppe; Benenti, Giuliano; Palma, G. Massimo

doi:10.1103/physreva.79.022105

Cited by 31 publications

(25 citation statements)

References 39 publications

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“…Collision models have been extensively used to describe open quantum systems [4,17,18], in particular thermalization processes [16,[21][22][23][24] and non-equilibrium scenarios in different thermodynamic contexts [25][26][27][28][29][30]. The main assumption is that when the system interacts with a bath, it collides and thereby interacts with only one particle of the bath at a time.…”

Section: Collision Modelmentioning

confidence: 99%

Imperfect Thermalizations Allow for Optimal Thermodynamic Processes

Bäumer

Perarnau-Llobet

Kammerlander

et al. 2019

Quantum

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Optimal (reversible) processes in thermodynamics can be modelled as step-bystep processes, where the system is successively thermalized with respect to different Hamiltonians by an external thermal bath. However, in practice interactions between system and thermal bath will take finite time, and precise control of their interaction is usually out of reach. Motivated by this observation, we consider finite-time and uncontrolled operations between system and bath, which result in thermalizations that are only partial in each step. We show that optimal processes can still be achieved for any non-trivial partial thermalizations at the price of increasing the number of operations, and characterise the corresponding tradeoff. We focus on work extraction protocols and show our results in two different frameworks: A collision model and a model where the Hamiltonian of the working system is controlled over time and the system can be brought into contact with a heat bath. Our results show that optimal processes are robust to noise and imperfections in small quantum systems, and can be achieved by a large set of interactions between system and bath.

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Section: Collision Modelmentioning

confidence: 99%

Imperfect Thermalizations Allow for Optimal Thermodynamic Processes

Bäumer

Perarnau-Llobet

Kammerlander

et al. 2019

Quantum

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“…Nonetheless, there are still important non-Markovian aspects in the intra-cycle dynamics. The full Markovian dynamics is obtained in the weak collision limit [73][74][75][76][77], where in each thermal stroke, the engine interacts weakly with many particles of the heat exchanger.…”

Section: The Coupling Of the Engine To The Heat Exchangers And To Thementioning

confidence: 99%

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

Uzdin

Levy

Kosloff

2016

Entropy

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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.

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“…Typically, in these collisions based baths the system that interacts with the bath is taken to be a single qubit but qudits and a chain of coupled qubits have been considered as well [46,47]. The collision model can also represent a general non-Markovian dynamics [48,49].…”

Section: Introductionmentioning

confidence: 99%

The multilevel four-stroke swap engine and its environment

Uzdin

Kosloff

2014

New J. Phys.

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A multilevel four-stroke engine where the thermalization strokes are generated by unitary collisions with thermal bath particles is analyzed. Our model is solvable even when the engine operates far from thermal equilibrium and in the strong system-bath coupling. Necessary operation conditions for the heat machine to perform as an engine or a refrigerator are derived. We relate the work and efficiency of the device to local and non-local statistical properties of the baths (purity, index of coincidence, etc) and put upper bounds on these quantities. Finally, in the ultra-hot regime, we analytically optimize the work and find a striking similarity to results obtained for efficiency at maximal power of classical engines. The complete swap limit of our results holds for any fourstroke quantum Otto engine that is coupled to the baths for periods that are significantly longer than the thermal relaxation time.

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Relaxation due to random collisions with a many-qudit environment

Cited by 31 publications

References 39 publications

Imperfect Thermalizations Allow for Optimal Thermodynamic Processes

Imperfect Thermalizations Allow for Optimal Thermodynamic Processes

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

The multilevel four-stroke swap engine and its environment

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