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Understanding the role of classical and quantum correlations in work extraction is a problem of fundamental importance in thermodynamics. We approach this problem by considering that, in closed quantum systems, the maximum cyclic work…

Quantum Physics · Physics 2022-05-18 Gianluca Francica

The principle of maximum entropy is a broadly applicable technique for computing a distribution with the least amount of information possible while constrained to match empirically estimated feature expectations. However, in many real-world…

Machine Learning · Computer Science 2022-08-16 Kenneth Bogert , Yikang Gui , Prashant Doshi

Work extraction protocol is always a significant issue in the context of quantum batteries, in which the notion of ergotropy is used to quantify a particular amount of energy that can be extracted through unitary processes. Given the total…

Quantum Physics · Physics 2021-10-04 F. H. Kamin , S. Salimi , Alan C. Santos

A subsystem of an entangled ground state is in a mixed state. Thus, if we isolate this subsystem from its surroundings we may be able to extract work applying unitary transformations, up to a maximal amount which is called ergotropy. Once…

We show that the maximum extractable work (ergotropy) from a quantum many-body system is constrained by local athermality of an initial state and local entropy decrease brought about by quantum operations. The obtained universal upper bound…

Quantum Physics · Physics 2025-01-31 Akihiro Hokkyo , Masahito Ueda

The expressive capacity of physical systems employed for learning is limited by the unavoidable presence of noise in their extracted outputs. Though present in physical systems across both the classical and quantum regimes, the precise…

Evaluating the maximum amount of work extractable from a nanoscale quantum system is one of the central problems in quantum thermodynamics. Previous works identified the free energy of the input state as the optimal rate of extractable work…

Quantum Physics · Physics 2026-03-06 Kaito Watanabe , Ryuji Takagi

Quantum coherence, encoded in the off-diagonal elements of a system's density matrix, is a key resource in quantum thermodynamics, fundamentally limiting the maximum extractable work known as ergotropy. While previous experiments have…

Quantum Physics · Physics 2025-12-04 Li Li , Silu Zhao , Yun-Hao Shi , Kai Xu , Heng Fan , Dongning Zheng , Zhongcheng Xiang

Calculating bounds of properties of many-body quantum systems is of paramount importance, since they guide our understanding of emergent quantum phenomena and complement the insights obtained from estimation methods. Recent semidefinite…

Quantum Physics · Physics 2026-01-16 Luke Mortimer , Leonardo Zambrano , Antonio Acín , Donato Farina

The extraction of information from a quantum system unavoidably implies a modification of the measured system itself. It has been demonstrated recently that partial measurements can be carried out in order to extract only a portion of the…

Quantum batteries are predicted to have the potential to outperform their classical counterparts and are therefore an important element in the development of quantum technologies. Of particular interest is the role of correlations in…

We examine the transport of useful energy, i.e. extractable work as quantified by the ergotropy, along a spin chain with tuneable exchange couplings between the sites. We focus on, and interpolate between, the two physically relevant limits…

Quantum Physics · Physics 2025-11-20 Dara Murphy , Anthony Kiely , Irene D'Amico , Steve Campbell

The second law of thermodynamics uses change in free energy of macroscopic systems to set a bound on performed work. Ergotropy plays a similar role in microscopic scenarios, and is defined as the maximum amount of energy that can be…

Quantum Physics · Physics 2022-10-19 Tanmoy Biswas , Marcin Łobejko , Paweł Mazurek , Konrad Jałowiecki , Michał Horodecki

A general achievable upper bound of extractable work under feedback control is given, where nonequilibrium equalities are generalized so as to be applicable to error-free measurements. The upper bound involves a term which arises from the…

Statistical Mechanics · Physics 2014-11-20 Yuto Ashida , Ken Funo , Yûto Murashita , Masahito Ueda

As quantum technologies advance, the ability to generate increasingly large quantum states has experienced rapid development. In this context, the verification and estimation of large entangled systems represents one of the main challenges…

Quantum Physics · Physics 2022-03-30 Joshua Morris , Valeria Saggio , Aleksandra Gočanin , Borivoje Dakić

Quantum state tomography is an integral part of quantum computation and offers the starting point for the validation of various quantum devices. One of the central tasks in the field of state tomography is to reconstruct with high fidelity,…

Quantum Physics · Physics 2022-12-21 Rishabh Gupta , Manas Sajjan , Raphael D. Levine , Sabre Kais

We introduce a cavity-coupled finite quantum system which can act as a quantum battery by harnessing noise induced coherences. We apply the methodology of full counting statistics to capture higher-order fluctuations of quanta exchange in…

We investigate the decomposition of ergotropy into incoherent and coherent contributions for quantum systems subject to typical Markovian noise channels. The incoherent part originates from population inversion in the energy eigenbasis…

Quantum Physics · Physics 2026-02-24 Mohammad B. Arjmandi

We consider the problem of learning the Hamiltonian of a quantum system from estimates of Gibbs-state expectation values. Various methods for achieving this task were proposed recently, both from a practical and theoretical point of view.…

Quantum Physics · Physics 2024-10-31 Adam Artymowicz , Hamza Fawzi , Omar Fawzi , Samuel O. Scalet

Cross-entropy benchmarking is a central technique used to certify a quantum chip in recent experiments. To better understand its mathematical foundation and develop new benchmarking schemes, we introduce the concept of ergodicity to random…

Quantum Physics · Physics 2025-02-14 Bin Cheng , Fei Meng , Zhi-Jiong Zhang , Man-Hong Yung