No-Go Theorem for the Characterization of Work Fluctuations in Coherent Quantum Systems

Perarnau-Llobet, Martí; Bäumer, Elisa; Hovhannisyan, Karen V.; Huber, Marcus; Acín, Antonio

doi:10.1103/physrevlett.118.070601

Cited by 190 publications

(245 citation statements)

References 58 publications

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“…Also, the work value associated with each time-reversed trajectory has obtained a minus sign, see equation (15), as time has inverted, t t D  -D .…”

Section: A Quantum Work Distribution From Power Trajectoriesmentioning

confidence: 99%

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Time-reversal symmetric work distributions for closed quantum dynamics in the histories framework

Miller

Anders

2017

New J. Phys.

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A central topic in the emerging field of quantum thermodynamics is the definition of thermodynamic work in the quantum regime. One widely used solution is to define work for a closed system undergoing non-equilibrium dynamics according to the two-point energy measurement scheme. However, due to the invasive nature of measurement the two-point quantum work probability distribution cannot describe the statistics of energy change from the perspective of the system alone. We here introduce the quantum histories framework as a method to characterise the thermodynamic properties of the unmeasured, closed dynamics. Constructing continuous power operator trajectories allows us to derive an alternative quantum work distribution for closed quantum dynamics that fulfils energy conservation and is time-reversal symmetric. This opens the possibility to compare the measured work with the unmeasured work, contrasting with the classical situation where measurement does not affect the work statistics. We find that the work distribution of the unmeasured dynamics leads to deviations from the classical Jarzynski equality and can have negative values highlighting distinctly non-classical features of quantum work.

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“…Also, the work value associated with each time-reversed trajectory has obtained a minus sign, see equation (15), as time has inverted, t t D  -D .…”

Section: A Quantum Work Distribution From Power Trajectoriesmentioning

confidence: 99%

“…Today research aims to link both quantum and classical stochasticity into a single quantum thermodynamic framework [6]. Defining fluctuating work for quantum processes, and with it a work distribution p(w) that characterises its statistical fluctuations, has been the subject of intense debate [7][8][9][10][11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Time-reversal symmetric work distributions for closed quantum dynamics in the histories framework

Miller

Anders

2017

New J. Phys.

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“…In this article, we report the experimental investigation of reducing quantum measurement back-action in work distribution by using collective measurements (CM) on two identically prepared qubit states. We implement the proposal of [18] in an all-optical setup, which can be used to efficiently simulate quantum coherent processes. The standard two projective energy measurement (TPM) scheme [1,2] to measure work is also experimentally sim- * gyxiang@ustc.edu.cn † marti.perarnau@mpq.mpg.de ulated for comparison.…”

Section: Introductionmentioning

confidence: 99%

Experimentally reducing the quantum measurement back action in work distributions by a collective measurement

Yuan

Xiang

et al. 2019

Sci. Adv.

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In quantum thermodynamics, the standard approach to estimating work fluctuations in unitary processes is based on two projective measurements, one performed at the beginning of the process and one at the end. The first measurement destroys any initial coherence in the energy basis, thus preventing later interference effects. To decrease this back action, a scheme based on collective measurements has been proposed by Perarnau-Llobetet al. Here, we report its experimental implementation in an optical system. The experiment consists of a deterministic collective measurement on two identically prepared qubit states, encoded in the polarization and path degree of a single photon. The standard two-projective measurement approach is also experimentally realized for comparison. Our results show the potential of collective schemes to decrease the back action of projective measurements, and capture subtle effects arising from quantum coherence.

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“…Regarding quantum definitions of work, several attempts have been made141516, but there is still no consensus on these definitions and their treatment of fluctuations. The problem of defining a truly quantum definition of work, or if such a definition exists, remains an important and open question161718.…”

Section: Resultsmentioning

confidence: 99%

Work extraction from quantum systems with bounded fluctuations in work

Richens

Masanes

2016

Nat Commun

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In the standard framework of thermodynamics, work is a random variable whose average is bounded by the change in free energy of the system. This average work is calculated without regard for the size of its fluctuations. Here we show that for some processes, such as reversible cooling, the fluctuations in work diverge. Realistic thermal machines may be unable to cope with arbitrarily large fluctuations. Hence, it is important to understand how thermodynamic efficiency rates are modified by bounding fluctuations. We quantify the work content and work of formation of arbitrary finite dimensional quantum states when the fluctuations in work are bounded by a given amount c. By varying c we interpolate between the standard and minimum free energies. We derive fundamental trade-offs between the magnitude of work and its fluctuations. As one application of these results, we derive the corrected Carnot efficiency of a qubit heat engine with bounded fluctuations.

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No-Go Theorem for the Characterization of Work Fluctuations in Coherent Quantum Systems

Cited by 190 publications

References 58 publications

Time-reversal symmetric work distributions for closed quantum dynamics in the histories framework

Time-reversal symmetric work distributions for closed quantum dynamics in the histories framework

Experimentally reducing the quantum measurement back action in work distributions by a collective measurement

Work extraction from quantum systems with bounded fluctuations in work

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