Work Extraction from Unknown Quantum Sources

Šafránek, Dominik; Rosa, Dario; Binder, Felix C.

doi:10.1103/physrevlett.130.210401

Cited by 20 publications

(3 citation statements)

References 87 publications

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“…In this paper, we focus on the problem of quantifying state activation in scenarios where quantum switch (QS) is applied. It is well known that passive state in quantum thermodynamics cannot be activated by any unitary operations [38][39][40][41][42], needing extra resources (e.g., coherences in the state) to be able to be used in thermodynamical tasks. With the rapid advancement of indefinite causal order (ICO) research in its quantum switch (QS) form , especially in the context of communication, computation and metrology, the matter of its resourcefulness in performing thermodynamic tasks is still open, apart from a few works on this topic [32][33][34][35].…”

Section: Discussionmentioning

confidence: 99%

“…State ρ S is passive with respect to the Hamiltonian system, H S , if [38][39][40] tr{ρ S H S } ≤ tr Uρ S U † H S (2) for every unitary operation U. The notion closely related with passivity of states is ergotropy [41,42] as it measures extractable work. The definition of ergotropy is the following: considering a quantum system whose state is ρ S and Hamiltonian is H S , the ergotropy of such system-or extractable work-is expressed by…”

Section: Quantum Switch and Passive States In Thermodynamicsmentioning

confidence: 99%

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Quantum Switch as a Thermodynamic Resource in the Context of Passive States

Molitor,

Rudnicki

2024

Entropy

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In recent years, many works have explored possible advantages of indefinite causal order, with the main focus on its controlled implementation known as quantum switch. In this paper, we tackle advantages in quantum thermodynamics, studying whether quantum switch is capable of activating a passive state, either alone or with extra resources (active control state) and/or operations (measurement of the control system). By disproving the first possibility and confirming the second one, we show that quantum switch is not a thermodynamic resource in the discussed context, though it can facilitate work extraction given external resources. We discuss our findings by considering specific examples: a qubit system subject to rotations around the x and y axes in the Bloch sphere, as well as general unitaries from the U(2) group; and the system as a quantum harmonic oscillator with displacement operators, as well as with a combination of displacement and squeeze operators.

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Section: Discussionmentioning

confidence: 99%

Section: Quantum Switch and Passive States In Thermodynamicsmentioning

confidence: 99%

Quantum Switch as a Thermodynamic Resource in the Context of Passive States

Molitor,

Rudnicki

2024

Entropy

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“…[1][2][3][4] in studies of non-equilibrium statistical mechanics as a useful unifying framework to describe coarse-grained entropy in classical and quantum systems, [5][6][7] with applications across thermodynamics and quantum information theory. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] In the quantum case, for any measurement described by a positive operator valued measures (POVM) M = (Mi)i ∈ I , (Mi ≥ 0, ∑ i Mi = 𝟙), and quantum state described by a density matrix ρ, observational entropy…”

Section: Introductionmentioning

confidence: 99%

Continuity bounds on observational entropy and measured relative entropies

Schindler,

Winter

2023

Journal of Mathematical Physics

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We derive a measurement-independent asymptotic continuity bound on the observational entropy for general positive operator valued measures measurements, making essential use of its property of bounded concavity. The same insight is used to obtain continuity bounds for other entropic quantities, including the measured relative entropy distance to a convex set of states under a general set of measurements. As a special case, we define and study conditional observational entropy, which is an observational entropy in one (measured) subsystem conditioned on the quantum state in another (unmeasured) subsystem. We also study continuity of relative entropy with respect to a jointly applied channel, finding that observational entropy is uniformly continuous as a function of the measurement. But we show by means of an example that this continuity under measurements cannot have the form of a concrete asymptotic bound.

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Impossibility of universal work extraction from coherence: reconciling axiomatic and resource-theory approaches

Plesnik,

Violaris

2024

New J. Phys.

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We compare how the impossibility of a universal work extractor from coherence arises from different approaches to quantum thermodynamics: an explicit protocol accounting for all relevant quantum resources, and axiomatic, information-theoretic constraints imposed by constructor theory. We first explain how the impossibility of a universal work extractor from coherence is directly implied by a recently proposed constructor-theoretic theorem based on distinguishability, which is scale- and dynamics- independent. Then we give an explicit demonstration of this result within quantum theory, by proving the impossibility of generalising a proposed quantum protocol for deterministically extracting work from coherence. We demonstrate a new connection between the impossibility of universal work extractors and constructor-based irreversibility, which was recently shown using the quantum homogenizer. Finally we discuss additional avenues for applying the constructor-theoretic formulation of work extraction to quantum thermodynamics, including the irreversibility of quantum computation and thermodynamics of multiple conserved quantities.

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Work Extraction from Unknown Quantum Sources

Cited by 20 publications

References 87 publications

Quantum Switch as a Thermodynamic Resource in the Context of Passive States

Quantum Switch as a Thermodynamic Resource in the Context of Passive States

Continuity bounds on observational entropy and measured relative entropies

Impossibility of universal work extraction from coherence: reconciling axiomatic and resource-theory approaches

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