arXiv subjects

Franco Mayo

Publications and source records attributed to Franco Mayo.

7 recordsLinked to original sources

arXiv2026

Finite-time thermal refrigerator in interacting Bose-Einstein Condensates

We study a finite-time thermodynamic refrigeration cycle realized numerically in three-dimensional, weakly interacting Bose-Einstein condensates (BECs). The setup consists of three spatially separated condensates -- system, piston, and reservoir -- coupled through time-dependent potential barriers that implement compression, expansion, and contact strokes. Finite-temperature initial states are generated with the Stochastic Ginzburg-Landau equation, and the subsequent dynamics are evolved using the truncated Gross-Pitaevskii equation. To measure temperatures we use a momentum-space thermometry method that provides estimates for each condensate. We find that despite mass transfer and sound excitations, the protocol achieves successful cooling during consecutive cycles: the first cycle lowers its temperature by ~20%, and a second cycle yields additional, though reduced, cooling, reaching a final ~27% cooling from the initial state. Our results show that interacting BECs can sustain finite-time quantum thermal cycles under realistic conditions, and provide a platform for exploring different refrigeration schemes, optimized control protocols, and shortcuts to adiabaticity.

cond-mat.quant-gas↗

arXiv2025

Quantum thermodynamic uncertainty relation and macroscopic superconducting coherence

Stability and efficiency are mutually exclusive in a thermodynamic process, e.g. in a thermal machine. Any effort to reduce the fluctuations of a certain output quantity is necessarily accompanied by an increase of entropy production, therefore lowering its efficiency. This interplay is beautifully captured by the so called Thermodynamic Uncertainty Relations (TURs) which set a lower bound on the relative uncertainty of a current for a given rate of entropy production. Their status in hybrid normal-superconducting (N-S) devices has remained unsettled. We show that, in the subgap regime, departures from the normal quantum TUR are governed by {\it macroscopic} superconducting coherence quantified by the pair amplitude, and that introducing a dephasing probe suppresses this coherence and restores the bound. We further derive a hybrid quantum TUR that is general for two-terminal N-S junctions in the Andreev regime: the inequality is never violated, is saturated only at vanishing current, and is related to the normal quantum bound under the replacement (e to 2e). For N-S quantum dot and Cooper-pair-splitter systems we compute current and noise and show that deviations from the normal bound track the pair amplitude on the central region. The results establish a direct link between superconducting macroscopic coherence and nonequilibrium fluctuations and supply a general bound for the Andreev regime.

cond-mat.mes-hall↗

arXiv2025

Purcell Enhancement and Suppression in Laser Cooling of Yb$^{3+}$:YLF Nanocrystals in a Fabry-P\'erot Microcavity

We investigate the improvement of anti-Stokes laser cooling of a Yb$^{3+}$:YLF nanocrystal in a Fabry-P\'erot microcavity via the Purcell effect. Our analysis accounts for both the enhancement of emission lines resonant with the cavity transmission and the suppression of off-resonance emissions. Using a quantum-mechanical framework, we modeled the Yb$^{3+}$ ions in a YLiF$_4$ matrix and the laser system to calculate the minimum achievable temperature and cooling efficiency, incorporating cavity-induced modifications to experimental data on emission cross section. Our results indicate that for temperatures below 100~K, the cooling efficiency ($\eta_c$) is consistently enhanced, and the minimum achievable temperature is reduced comfortably below the current limits. We also show how the inclusion of Purcell inhibition effects can lead to improvements in the cooling efficiency ranging from 25\% to 65\%, with respect to the case when only Purcell enhancement is considered.

quant-ph↗

arXiv2024

Enhancing the efficiency of quantum measurement-based engines with entangling measurements

We study the impact of entangling measurements on the efficiency of quantum measurement- based engines. We first show that for engines comprising many subsystems their efficiency can be enhanced by performing entangling measurements, as opposed to local measurements over each subsystem. When the collective measurement produces the same local state for the subsystems as individual local measurements, the improvement in the efficiency is proportional to the amount of correlations. Finally, we show that for two level systems these type of engine can operate at perfect efficiency while yielding a finite amount of work, in the limit large the number of subsystems.

quant-ph↗

arXiv2023

Quantum engines with interacting Bose-Einstein condensates

We consider a quantum Otto cycle with an interacting Bose-Einstein condensate at finite temperature. We present a procedure to evolve this system in time in three spatial dimensions, in which closed (adiabatic) strokes are described by the Gross-Pitaevskii equation, and open (isochoric) strokes are modeled using a stochastic Ginzburg-Landau equation. We analyze the effect on the thermodynamic efficiency of the strength of interactions, the frequency of the harmonic trap, and the temperatures of the reservoirs. The efficiency has little sensitivity to changes in the temperatures, but decreases as interactions increase. However, stronger interactions allow for faster cycles and for substantial increases in power.

quant-ph↗

arXiv2023

A Wigner quasiprobability distribution of work

In this article we introduce a quasiprobability distribution of work that is based on the Wigner function. This construction rests on the idea that the work done on an isolated system can be coherently measured by coupling the system to a quantum measurement apparatus. In this way, a quasiprobability distribution of work can be defined in terms of the Wigner function of the apparatus. This quasidistribution contains the information of the work statistics and also holds a clear operational definition. Moreover, it is shown that the presence of quantum coherence in the energy eigenbasis is related with the appearance of characteristics related to non-classicality in the Wigner function such as negativity and interference fringes. On the other hand, from this quasiprobability distribution it is straightforward to obtain the standard two-point measurement probability distribution of work and also the difference in average energy for initial states with coherences.

quant-ph↗

arXiv2022

Collective effects and quantum coherence in dissipative charging of quantum batteries

We consider the dissipative charging process of quantum batteries in terms of a collisional model, where the batteries are coupled to a heat bath using non-energy preserving interactions. First, we show that for low temperatures the collective process can attain a charging power that increases polynomically with the number of batteries. The scaling we find is $N^3$ that, while being grater than the bound obtained for unitary processes, it has a lower efficiency. Then, we study the dissipative charging process of single battery using a time dependent Hamiltonian that generates coherences in the energy basis. In this case we find that the presence of coherence could enhance the charging power and also its efficiency. Finally, we show how this process can be used in a quantum heat engine that contains the charging process as one of its open strokes.

quant-ph↗