Quantum Coherence and Ergotropy

Francica, Gianluca; Binder, Felix C.; Guarnieri, Giacomo; Mitchison, Mark T.; Goold, John; Plastina, Francesco

doi:10.1103/physrevlett.125.180603

Cited by 141 publications

(101 citation statements)

References 96 publications

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“…The next step is to extend the results to quantum batteries in coherent states. The recent paper [37] is possibly the first step in such a direction. E Derivation of Equation 5Since the metric is bi-invariant, so is the geodesic distance.…”

Section: Discussionmentioning

confidence: 98%

Time-optimal quantum transformations with bounded bandwidth

Allan

Hörnedal

Andersson

2021

Quantum

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In this paper, we derive sharp lower bounds, also known as quantum speed limits, for the time it takes to transform a quantum system into a state such that an observable assumes its lowest average value. We assume that the system is initially in an incoherent state relative to the observable and that the state evolves according to a von Neumann equation with a Hamiltonian whose bandwidth is uniformly bounded. The transformation time depends intricately on the observable's and the initial state's eigenvalue spectrum and the relative constellation of the associated eigenspaces. The problem of finding quantum speed limits consequently divides into different cases requiring different strategies. We derive quantum speed limits in a large number of cases, and we simultaneously develop a method to break down complex cases into manageable ones. The derivations involve both combinatorial and differential geometric techniques. We also study multipartite systems and show that allowing correlations between the parts can speed up the transformation time. In a final section, we use the quantum speed limits to obtain upper bounds on the power with which energy can be extracted from quantum batteries.

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Section: Discussionmentioning

confidence: 98%

Time-optimal quantum transformations with bounded bandwidth

Allan

Hörnedal

Andersson

2021

Quantum

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“…Our work sheds light on the formal connection between the theory of quantum coherence and recent attempts at going beyond the limitation of the TPM to unveil the statistics of energy fluctuations resulting from quantum processes. Such connection, which is becoming increasingly apparent in light of recent work [ 3 , 4 , 7 , 8 ], is likely to embody the leit motif of future endeavours aimed at pinpointing the potential advantages of quantum (thermo-)devices.…”

Section: Discussionmentioning

confidence: 99%

“…In the quest for the understanding of the interplay between thermal and quantum fluctuations that determine the energy exchange processes occurring at the nano- and micro-scale, the identification of the role played by quantum coherences is paramount [ 1 , 2 ]. The foundational nature of such understanding has been the driving force for much research effort, which has started shedding light onto the role that quantum coherence has in the quantum thermodynamic phenomenology, from work extraction to the emergence of irreversibility [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. Owing to the success that it has encountered in classical stochastic thermodynamics, the current approach to the determination of the statistics of such energetics in the quantum domain is based on the so-called two-point measurement (TPM) protocol [ 13 , 14 , 15 ]: the energy change of a system driven by a time-dependent protocol is measured both at the initial and final time of the dynamics.…”

Section: Introductionmentioning

confidence: 99%

“…Several strategies beyond the TPM scheme have been pointed out in this line [ 5 , 6 , 7 , 21 , 22 , 23 , 24 , 32 ]. Here, we will consider the MH scheme for measuring work, which replaces the first projective measurement of the TPM scheme with a weak measurement [ 23 ], and thus allows for initial coherence to survive along the protocol.…”

Section: Introductionmentioning

confidence: 99%

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Quantum Work Statistics with Initial Coherence

Díaz

Guarnieri

Paternostro

2020

Entropy

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The two-point measurement scheme for computing the thermodynamic work performed on a system requires it to be initially in equilibrium. The Margenau–Hill scheme, among others, extends the previous approach to allow for a non-equilibrium initial state. We establish a quantitative comparison between both schemes in terms of the amount of coherence present in the initial state of the system, as quantified by the l1-coherence measure. We show that the difference between the two first moments of work, the variances of work, and the average entropy production obtained in both schemes can be cast in terms of such initial coherence. Moreover, we prove that the average entropy production can take negative values in the Margenau–Hill framework.

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“…It can be extracted from the QB at a given time t of its evolution (charging). In general, this quantity is different from the stored energy due to the fact that part of the energy may be locked into correlations and, therefore, cannot be extracted for further purposes [ 67 ]. A general derivation of this quantity starts from the Hamiltonian of the QB, written as [ 10 ]

with the energy eigenvalues ordered, such that

and with

associated eigenvectors, as well as the density matrix at a given time

ordered, such that

and with

eigenvectors.…”

Section: Figures Of Merit Of the Quantum Batterymentioning

confidence: 99%

Characterization of a Two-Photon Quantum Battery: Initial Conditions, Stability and Work Extraction

Delmonte

Crescente

Carrega

et al. 2021

Entropy

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We consider a quantum battery that is based on a two-level system coupled with a cavity radiation by means of a two-photon interaction. Various figures of merit, such as stored energy, average charging power, energy fluctuations, and extractable work are investigated, considering, as possible initial conditions for the cavity, a Fock state, a coherent state, and a squeezed state. We show that the first state leads to better performances for the battery. However, a coherent state with the same average number of photons, even if it is affected by stronger fluctuations in the stored energy, results in quite interesting performance, in particular since it allows for almost completely extracting the stored energy as usable work at short enough times.

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Quantum Coherence and Ergotropy

Cited by 141 publications

References 96 publications

Time-optimal quantum transformations with bounded bandwidth

Time-optimal quantum transformations with bounded bandwidth

Quantum Work Statistics with Initial Coherence

Characterization of a Two-Photon Quantum Battery: Initial Conditions, Stability and Work Extraction

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