Work extraction and energy storage in the Dicke model

Abstract

We study work extraction from the Dicke model achieved using simple unitary cyclic transformations keeping into account both a non optimal unitary protocol, and the energetic cost of creating the initial state. By analyzing the role of entanglement, we find that highly entangled states can be inefficient for energy storage when considering the energetic cost of creating the state. Such surprising result holds notwithstanding the fact that the criticality of the model at hand can sensibly improve the extraction of work. While showing the advantages of using a many-body system for work extraction, our results demonstrate that entanglement is not necessarily advantageous for energy storage purposes, when non optimal processes are considered. Our work shows the importance of better understanding the complex interconnections between non-equilibrium thermodynamics of quantum systems and correlations among their subparts.

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

“…As a consequence, while the observation of work fluctuations does not change the work output for macroscopic processes, this is no longer true in quantum systems with coherence. This result sheds light on the crucial role of measurements [25,[41][42][43][44][45][46] and coherence [47][48][49][50][51][52] in quantum thermodynamics, and seems to imply that there will probably never be an equivalently universal notion of a work variable that is independent of the context in quantum mechanics.…”

Thermodynamics of ultrastrongly coupled light-matter systems

“…Therefore, such artificial light-matter systems constitute an ideal testbed for studying strongly-coupled quantum systems with unconventional thermodynamical properties. Potentially, this can also lead to more accurate descriptions of fundamental thermodynamical processes or the optimization of quantum thermal machines, for which cavity QED and collective spin models have already been considered as simple toy systems in the past [71,72,73,74,75,76]. thus expected that for N 1 the phase transition point is accurately predicted by the mean-field Hamiltonian…”

Powerful harmonic charging in a quantum battery

“…It is interesting to study the properties of QBs in different phases related to quantum correlations, which should be on a close relation to the collective charging. For example, the connection between the phase transition induced by the QB-charger coupling and the optimal energy stor- * Electronic address: yuyuzh@cqu.edu.cn † Electronic address: lbfu@gscaep.ac.cn ‡ Electronic address: xgwang1208@zju.edu.cn age has recently been studied [7,8]. However, the effects of quantum correlations in the other kind of QBs with intrinsic interactions between batteries, especially a phase transition, are overlooked.…”