A quantum Szilard engine without heat from a thermal reservoir

Mohammady, M. Hamed; Anders, Janet

doi:10.1088/1367-2630/aa8ba1

Cited by 52 publications

(30 citation statements)

References 51 publications

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“…The above expression implies that, if U commutes with the total Hamiltonian H = H S (τ ) + H A (τ ) = H S (0) + H A (0), then W M ρ (x) = 0 for all outcomes x and initial states ρ. This strengthens previous results, which only established that the average work vanishes when U and Z A commute with the total Hamiltonian [47].…”

Section: Work Statistics For Measurementssupporting

confidence: 91%

Conditional work statistics of quantum measurements

Mohammady

Romito

2019

Quantum

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In this paper we introduce a definition for conditional energy changes due to general quantum measurements, as the change in the conditional energy evaluated before, and after, the measurement process. By imposing minimal physical requirements on these conditional energies, we show that the most general expression for the conditional energy after the measurement is simply the expected value of the Hamiltonian given the post-measurement state. Conversely, the conditional energy before the measurement process is shown to be given by the real component of the weak value of the Hamiltonian. Our definition generalises well-known notions of distributions of internal energy change, such as that given by stochastic thermodynamics. By determining the conditional energy change of both system and measurement apparatus, we obtain the full conditional work statistics of quantum measurements, and show that this vanishes for all measurement outcomes if the measurement process conserves the total energy. Additionally, by incorporating the measurement process within a cyclic heat engine, we quantify the non-recoverable work due to measurements. This is shown to always be nonnegative, thus satisfying the second law, and will be independent of the apparatus specifics for two classes of projective measurements.Accepted in Quantum 2019-07-30, click title to verify. Published under CC-BY 4.0. arXiv:1809.09010v6 [quant-ph]

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Section: Work Statistics For Measurementssupporting

confidence: 91%

Conditional work statistics of quantum measurements

Mohammady

Romito

2019

Quantum

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“…Thus, quantum measurement plays an important role in quantum thermodynamics. Energetic cost for performing a measurement [ 49 , 50 , 51 , 52 , 53 ] and using the average energy change due to the measurement for extracting useful work are two important facets of quantum thermodynamics. In a subsequent work [ 54 ], the authors calculated the detailed fluctuation of work and heat in the above said measurement driven single temperature heat engine without feedback control as well as considered the finite power scenario.…”

Section: Introductionmentioning

confidence: 99%

Measurement Based Quantum Heat Engine with Coupled Working Medium

Das

Ghosh

2019

Entropy

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We consider measurement based single temperature quantum heat engine without feedback control, introduced recently by Yi, Talkner and Kim [Phys. Rev. E 96, 022108 (2017)]. Taking the working medium of the engine to be a one-dimensional Heisenberg model of two spins, we calculate the efficiency of the engine undergoing a cyclic process. Starting with two spin-1/2 particles, we investigate the scenario of higher spins also. We show that, for this model of coupled working medium, efficiency can be higher than that of an uncoupled one. However, the relationship between the coupling constant and the efficiency of the engine is rather involved. We find that in the higher spin scenario efficiency can sometimes be negative (this means work has to be done to run the engine cycle) for certain range of coupling constants, in contrast to the aforesaid work of Yi, Talkner and Kim, where they showed that the extracted work is always positive in the absence of coupling. We provide arguments for this negative efficiency in higher spin scenarios. Interestingly, this happens only in the asymmetric scenarios, where the two spins are different. Given these facts, for judiciously chosen conditions, an engine with coupled working medium gives advantage for the efficiency over the uncoupled one.

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“…For instance, there are obstacles to the implementation of quantum logic gates [6][7][8]. The theorem continues to inspire research in a variety of directions (some recent examples are [9][10][11][12][13][14][15]), and connections have been made to other fields of research; for instance in the resource theories of asymmetry [16] and coherence [17,18], the theory of quantum reference frames [19], quantum clocks [20], and quantum thermodynamics [21][22][23][24][25]. Despite this ongoing development, the full scope of the WAY theorem is not known; particularly, the role of disturbance has not yet been carefully examined.…”

Section: Introductionmentioning

confidence: 99%