检索结果-内蒙古大学图书馆

Monitored quantum unital Otto heat engines: Fluctuations of the released heat and entropy production

学校读者我要写书评

暂无评论

Physica A: Statistical Mechanics and its Applications 2025年 669卷

作者： El Makouri, Abdelkader Slaoui, Abdallah Ahl Laamara, Rachid LPHE-Modeling and Simulation Faculty of Sciences Mohammed V University in Rabat Morocco Centre of Physics and Mathematics CPM CNESTEN Rabat Morocco

Recently, we have considered a single-qubit quantum Otto cycle based on arbitrary (non-unitary) unital channels as a heat source. We showed similarly to some works in literature that the ratio of the fluctuations of work (W) and heat absorbed (QM) is lower-and-upper bounded. In this paper, we drive this line of research further and consider the fluctuations of the stochastic heat exchanged (denoted by QC′) with the cold bath. In general, there is another stochastic quantity, which we denote by QC, that gives the same average as QC′ − but not higher cumulants. While QC′ is defined through the two-point measurement scheme, i.e., by measuring the energy of the working medium in all four strokes, QC follows from imposing the first of thermodynamics at the stochastic level. Our work has two important results: (i) first, we prove that the measurement of the working medium during three strokes is sufficient to construct the distribution of QC′ (ii) and that the cumulants of the stochastic entropy production denoted by Σ can be inferred from the cumulants of QC. © 2025 Elsevier B.V.

关键词： Otto cycle

Unlocking thermodynamic multitasking: Exploring the functioning of two-qubit engines through coherence and entanglement

学校读者我要写书评

暂无评论

arXiv 2025年

作者： Tarif, Hachem Slaoui, Abdallah Laamara, Rachid Ahl LPHE-Modeling and Simulation Faculty of Sciences Mohammed V University in Rabat Rabat Morocco Centre of Physics and Mathematics CPM Faculty of Sciences Mohammed V University in Rabat Rabat Morocco

Recent studies have investigated the role of entanglement in the operation of a two-qubit system as a heat engine, showing that work can be extracted from a single heat bath without direct heat dissipation between the two-qubit system and the cold bath (2021 Phys. Rev. Lett, 126 120605). In this work, we explore the impact of operating the same two-qubit system model with two heat baths and direct dissipation to the environment by applying both a local and a global Markovian master equation. The addition of a second heat bath enables the system to operate in different modes depending on the initial quantum state. We examine the temporal behavior of concurrence entanglement and quantum coherence, analyzing their observable roles in transitions between various operational regimes. Additionally, we investigate the evolution of information flow throughout the working cycle of the two-qubit system, focusing on the influence of individual and collective decoherence on the system’s efficiency and operational modes. We identify the optimal parameter regions for the engine and refrigerator modes to achieve maximum performance. Finally, we investigate the effect of coherence outside the system on its thermodynamic quantities. © 2025, CC0.

关键词： Qubits

100 Particles Quantum Heat Engine: Exploring the Impact of Criticality on Efficiency

学校读者我要写书评

暂无评论

arXiv 2025年

作者： Hminat, Anass Slaoui, Abdallah Amghar, Brahim Laamara, Rachid Ahl LPHE-Modeling and Simulation Faculty of Sciences Mohammed V University in Rabat Rabat Morocco Centre of Physics and Mathematics CPM Faculty of Sciences Mohammed V University in Rabat Rabat Morocco Laboratory LPNAMME Laser Physics Group Department of Physics Faculty of Sciences Chouaïb Doukkali University El Jadida Morocco

Quantum many-body systems present substantial technical challenges from both analytical and numerical perspectives. Despite these difficulties, some progress has been made, including studies of interacting atomic gases and interacting quantum spins. Furthermore, the potential for criticality to enhance engine performance has been demonstrated, suggesting a promising direction for future investigation. Here, we explore the performance of a quantum Otto cycle using a long-range Ising chain as the working substance. We consider an idealized cycle consisting of two adiabatic transformations and two perfect thermalizations, eliminating dissipation. Analyzing both engine and refrigerator modes, we investigate the influence of particle number, varied from 10 to 100, on efficiencies and behavior near the critical point of the phase transition, which we characterize using a scaling factor. We also examine how internal factors—specifically, the power-law exponent, the number of particles, and the hot and cold reservoir temperatures—affect the system’s operation in different modes. Our results reveal that these factors have a different impact compared to their classical counterparts. © 2025, CC0.

关键词： Otto cycle

On a biseparability criterion of bipartite qudit state

学校读者我要写书评

暂无评论

Chinese Physics B 2019年第8期28卷 42-49页

作者： B Benzimoun M Daoud LPHE-Modeling and Simulation Faculty of SciencesUniversity Mohammed ⅤRabatMorocco Department of Physics Faculty of Sciences-Ain ChockUniversity Hassan ⅡCasablancaMorocco Abdus Salam International Centre for Theoretical Physics TriesteItaly

In this paper,we propose a new approach to tackle the separability problem for bipartite qudit *** is based on the Majorana representation which allows to represent a N-spinors(qudit)as a symmetric state of N spin-1/*** also discuss how we can exploit such representation and the notion of the biseparability of multipartite qubit states in the sense to establish new criteria of the separability problem based on the PPT and concurrence.

关键词： separability bipartite qubit state partial separability Majorana representation

Quantum synchronization and entanglement of two magnon modes in a magnomechanical system

学校读者我要写书评

暂无评论

arXiv 2025年

作者： Harraf, Hamza Amazioug, Mohamed Laamara, Rachid Ahl LPHE-Modeling and Simulation Faculty of Sciences Mohammed V University in Rabat Rabat Morocco LPTHE-Department of Physics Faculty of Sciences Ibnou Zohr University Agadir80000 Morocco Centre of Physics and Mathematics CPM Faculty of Sciences Mohammed V University in Rabat Rabat Morocco

We investigate theoretically the improvement of the entanglement between the indirectly coupled two magnon modes in a magnomechanical system with magnon squeezing. We quantify the degree of entanglement via logarithmic negativity between two magnon modes. We show a significant enhancement of entanglement via magnon squeezing. Additionally, the entanglement of two magnons decreases monotonically under thermal effects. We demonstrate that with an increasing photon tunneling rate, entanglement is robust and resistant to thermal effects. We use purity as a witness to the mixing between the two magnon modes. We show that synchronization and purity are very robust against thermal effects rather than entanglement. We examine the relationship between quantum entanglement, purity, and quantum synchronization in both steady and dynamic states. According to our results, this scheme could be a promising platform for studying macroscopic quantum phenomena. Copyright © 2025, The Authors. All rights reserved.

关键词： Quantum entanglement

Analyzing emotions in online classes: Unveiling insights through topic modeling, statistical analysis, and random walk techniques

学校读者我要写书评

暂无评论

International Journal of Cognitive Computing in Engineering 2024年第1期5卷 221-236页

作者： Abdellaoui, Benyoussef Remaida, Ahmed Sabri, Zineb Abdellaoui, Mohammed El Hafidy, Abderrahim El Bouzekri El Idrissi, Younes Moumen, Aniss National School of Applied Sciences Engineering Sciences Laboratory Ibn Tofaïl University Kenitra Morocco Faculty of Sciences Laboratory of Computer Science Ibn Tofaïl University Kenitra Morocco LPHE-modeling and Simulation Faculty of Sciences Mohammed V University Rabat Morocco Software Project Management Research Team ENSIAS Mohammed V University Rabat Morocco

High dropout rates globally perpetuate educational disparities with various underlying causes. Despite numerous strategies to address this issue, more attention should be given to understanding and addressing student emotions during classes. This lack of focus adversely affects learner engagement and retention rates. While previous studies on online learning have primarily emphasized the effectiveness of technology, infrastructure, cognition, motivation, and economic benefits, there is still a gap in understanding the emotional aspects of distance learning. First, this study addresses this gap by employing thematic modeling and utilizing non-negative matrix factorization (NMF) for emotion recognition through students’ deep learning techniques and facial emotion recognition (FER). Second, statistical analysis of these findings further augments the depth of the study. Finally, the research proposes a mathematical model based on the random walk of emotional state transitions. The findings of this study underscore the importance of considering emotions in distance learning environments and their significant impact on student's academic performance and satisfaction. By acknowledging and addressing these emotional factors, educators can enhance learner engagement, promote positive emotions, mitigate negative emotions during online learning, and ultimately improve the effectiveness of online courses. © 2024 The Authors

关键词： Emotion Recognition

Monitored nonadiabatic and coherent-controlled quantum unital Otto heat engines: First four cumulants

学校读者我要写书评

暂无评论

Physical Review E 2023年第4期108卷 044114-044114页

作者： Abdelkader El Makouri Abdallah Slaoui Rachid Ahl Laamara LPHE-Modeling and Simulation Faculty of Sciences Mohammed V University in Rabat Rabat Morocco Centre of Physics and Mathematics CPM Faculty of Sciences Mohammed V University in Rabat Rabat Morocco

Recently, measurement-based quantum thermal machines have drawn more attention in the field of quantum thermodynamics. However, the previous results on quantum Otto heat engines were either limited to special unital and nonunital channels in the bath stages, or a specific driving protocol at the work strokes and assuming the cycle being time-reversal symmetric, i.e., V†=U (or V=U). In this paper, we consider a single spin-1/2 quantum Otto heat engine, by first replacing one of the heat baths by an arbitrary unital channel, and then we give the exact analytical expression of the characteristic function from which all the cumulants of heat and work emerge. We prove that under the effect of monitoring, ν2>ν1 is a necessary condition for positive work, either for a symmetric or asymmetric-driven Otto cycle. Furthermore, going beyond the average we show that the ratio of the fluctuations of work and heat is lower and upper-bounded when the system is working as a heat engine. However, differently from the previous results in the literature, we consider the third and fourth cumulants as well. It is shown that the ratio of the third (fourth) cumulants of work and heat is not upper-bounded by unity nor lower-bounded by the third (fourth) power of the efficiency, as is the case for the ratio of fluctuations. Finally, we consider applying a specific unital map that plays the role of a heat bath in a coherently superposed manner, and we show the role of the initial coherence of the control qubit on efficiency, on the average work and its relative fluctuations.

关键词： Open quantum systems & decoherence Quantum information theory Quantum thermodynamics

Ultimate precision of joint parameter estimation under noisy Gaussian environment

学校读者我要写书评

暂无评论

arXiv 2022年

作者： Bakmou, Lahcen Daoud, Mohammed LPHE-Modeling and Simulation Faculty of Sciences Mohammed V University Rabat Morocco Department of Physics Faculty of Sciences University Ibn Tofail Kenitra Morocco

The major problem of multiparameter quantum estimation theory is to find an ultimate measurement scheme to go beyond the standard quantum limits that each quasi-classical estimation measurement is limited by. Although, in some specifics quantum protocols without environmental noise, the ultimate sensitivity of a multiparameter quantum estimation can beat the standard quantum limit. However, the presence of noise imposes limitations on the enhancement of precision due to the inevitable existence of environmental fluctuations. Here, we address the motivation behind the usage of Gaussian quantum resources and their advantages in reaching the standard quantum limits under realistic noise. In this context, our work aims to explore the ultimate limits of precision for the simultaneous estimation of a pair of parameters that characterize the displacement channel acting on Gaussian probes and subjected to open dynamics. More precisely, we focus on a general two-mode mixed squeezed displaced thermal state, after reducing it to various Gaussian probes states, like;a two-mode pure squeezed vacuum, two-mode pure displaced vacuum, two-mode mixed displaced thermal, two-mode mixed squeezed thermal. To study the ultimate estimation precision, we evaluate the upper and bottom bound of HCRB in various cases. We find that when the entangled states, two-mode pure squeezed vacuum and two-mode mixed squeezed thermal, are employed as probes states, the upper and bottom bound of HCRB beats the standard quantum limit in the presence of a noisy environment. Copyright © 2022, The Authors. All rights reserved.

关键词： Gaussian distribution

Monitored non-adiabatic and coherent-controlled quantum unital Otto heat engines: First four cumulants

学校读者我要写书评

暂无评论

arXiv 2023年

作者： Makouri, Abdelkader El Slaoui, Abdallah Laamara, Rachid Ahl LPHE-Modeling and Simulation Faculty of Sciences Mohammed V University in Rabat Morocco Centre of Physics and Mathematics CPM Faculty of Sciences Mohammed V University in Rabat Rabat Morocco

Recently, measurement-based quantum thermal machines have drawn more attention in the field of quantum thermodynamics. However, the previous results on quantum Otto heat engines were either limited to special unital and non-unital channels in the bath stages, or a specific driving protocol at the work strokes and assuming the cycle being time-reversal symmetric i.e. V † = U (or V = U). In this paper, we consider a single spin-1/2 quantum Otto heat engine, by first replacing one of the heat baths by an arbitrary unital channel and then we give the exact analytical expression of the characteristic function from which all the cumulants of heat and work emerge. We prove that under the effect of monitoring, ν2 > ν1 is a necessary condition for positive work, either for a symmetric or asymmetric-driven Otto cycle. Furthermore, going beyond the average we show that the ratio of the fluctuations of work and heat is lower and upper-bounded when the system is working as a heat engine. However, differently from the previous results in the literature, we consider the third and fourth cumulants as well. It is shown that the ratio of the third (fourth) cumulants of work and heat is not upper-bounded by unity nor lower-bounded by the third (fourth) power of the efficiency, as is the case for the ratio of fluctuations. Finally, we consider applying a specific unital map that plays the role of a heat bath in a coherently superposed, manner and we show the role of the initial coherence of the control qubit on efficiency, on the average work and its relative fluctuations. © 2023, CC0.

关键词： Otto cycle