arXiv subjects

Camille L Latune

Publications and source records attributed to Camille L Latune.

5 recordsLinked to original sources

arXiv2025

Quantum Thermodynamics and Quantum Perspectives

After a brief historical perspective, we introduce the key notions of work and heat for quantum systems, to then apply them to quantum engines operating on quantum Otto and Carnot cycles. The irreversible and dissipative character of the quantum Otto cycle is briefly analyzed, contrasting with the energetic optimality of the quantum Carnot cycle. The central question of quantum effects is also addressed and illustrated with several examples. Finally, the last part strives to explain the role that quantum thermodynamics plays for quantum applications and quantum technologies, particularly in relation to energy optimization and the trade-off between performances and energy costs.

quant-ph↗

arXiv2025

A thermodynamically consistent approach to the energy costs of quantum measurements

Considering a general microscopic model for a quantum measuring apparatus comprising a quantum probe coupled to a thermal bath, we analyze the energetic resources necessary for the realization of a quantum measurement, which includes the creation of system-apparatus correlations, the irreversible transition to a statistical mixture of definite outcomes, and the apparatus resetting. Crucially, we do not resort to another quantum measurement to capture the emergence of objective measurement results, but rather exploit the properties of the thermal bath which redundantly records the measurement result in its degrees of freedom, naturally implementing the paradigm of quantum Darwinism. In practice, this model allows us to perform a quantitative thermodynamic analysis of the measurement process. From the expression of the second law, we show how the minimal required work depends on the energy variation of the system being measured plus information-theoretic quantities characterizing the performance of the measurement -- efficiency and completeness. Additionally, we show that it is possible to perform a thermodynamically reversible measurement, thus reaching the minimal work expenditure, and provide the corresponding protocol. Finally, for finite-time measurement protocols, we illustrate the increasing work cost induced by rising entropy production inherent in finite-time thermodynamic processes. This highlights an emerging trade-off between velocity of the measurement and work cost, on top of a trade-off between efficiency of the measurement and work cost. We apply those findings to bring new insights in the thermodynamic balance of the measurement-powered quantum engines.

quant-ph↗

arXiv2024

Steady state in strong system-bath coupling: mean force Gibbs state versus reaction coordinate

Motivated by the growing importance of strong system-bath coupling in several branches of quantum information and related technological applications, we analyze and compare two strategies currently used to obtain (approximately) steady states in strong coupling. The first strategy is based on perturbative expansions while the second one uses reaction coordinate mapping. Focusing on the widely used spin-boson model, we show that, as expected and hoped, the predictions of these two strategies coincide for some parameter regions. This confirms and strengthens the relevance of both techniques. Beyond that, it is also crucial to know precisely their respective range of validity. In that perspective, thanks to their different limitations, we use one to benchmark the other. We introduce and successfully test some very simple validity criteria for both strategies, bringing some answers to the question of the validity range.

quant-ph↗

arXiv2022

Steady state in ultrastrong coupling regime: perturbative expansion and first orders

Understanding better the dynamics and steady states of systems strongly coupled to thermal baths is a great theoretical challenge with promising applications in several fields of quantum technologies. Among several strategies to gain access to the steady state, one consists in obtaining approximate expressions of the mean force Gibbs state, the reduced state of the global system-bath thermal state, largely credited to be the steady state. Here, we present analytical expressions of corrective terms to the ultrastrong coupling limit of the mean force Gibbs state, which has been recently derived. We find that the first order term precisely coincides with the first order correction obtained from a dynamical approach -- master equation in the strong-decoherence regime. This strengthens the identification of the reduced steady state with the mean force Gibbs state. Additionally, we also compare our expressions with another recent result obtained from a high temperature expansion of the mean force Gibbs state. We observe numerically a good agreement for ultra strong coupling as well as for high temperatures. This confirms the validity of all these results. In particular, we show that, in term of coherences, all three results allow one to sketch the transition from ultrastrong coupling to weak coupling.

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arXiv2021

Energetic advantages of non-adiabatic drives combined with non-thermal quantum states

Unitary drivings of quantum systems are ubiquitous in experiments and applications of quantum mechanics and the underlying energetic aspects, particularly relevant in quantum thermodynamics, are receiving growing attention. We investigate energetic advantages in unitary driving obtained from initial non-thermal states. We introduce the non-cyclic ergotropy to quantify the energetic gains, from which coherent (coherence-based) and incoherent (population-based) contributions are identified. In particular, initial quantum coherences appear to be always beneficial whereas non-passive population distributions not systematically. Additionally, these energetic gains are accessible only through non-adiabatic dynamics, contrasting with the usual optimality of adiabatic dynamics for initial thermal states. Finally, following frameworks established in the context of shortcut-to-adiabaticity, the energetic cost related to the implementation of the optimal drives are analysed and, in most situations, are found to be smaller than the energetic cost associated with shortcut-to-adiabaticity. We treat explicitly the example of a two-level system and show that energetic advantages increase with larger initial coherences, illustrating the interplay between initial coherences and the ability of the dynamics to consume and use coherences.

quant-ph↗