Articles
Physica A: Statistical Mechanics and its Applications (03784371)669
In this paper, we explore a quantum Otto cycle with a quantum harmonic oscillator on a circle as its working substance. Since the eigenenergies of this oscillator depend on the curvature of the circle, this model, as an analog model, enables us to investigate the curvature effects of the physical space on properties of quantum heat engines. We consider two classical hot and cold thermal baths located in regions with different curvatures. By calculating the curvature-dependent work and heat in the Otto cycle, we emphasize the role of curvature in determining the thermal efficiency of the heat engine. Notably, we demonstrate that by adjusting the curvature difference between the bath locations, the engine's efficiency can approach the Carnot limit. © 2025 Elsevier B.V.
Physica A: Statistical Mechanics and its Applications (03784371)674
In this paper, we construct thermal nonlinear coherent states on the circumference of a circle and demonstrate that these states are fundamentally two-mode squeezed nonlinear coherent states of the circle at absolute zero temperature. Next, we examine the quantum statistical characteristics of states. Specifically, we explore how temperature enhancement influences the transition of the constructed states from nonclassical states to classical, measured by the Mandel parameter, at a so called transition temperature. We show that the amount of the transition temperature is increased by increasing the curvature of the circle. It appears that an increase in spatial curvature enables nonlinear coherent states to retain their nonclassical properties at higher temperature levels. © 2025 Elsevier B.V.
Physical Review A (24699934)110(1)
Entanglement formation between the magnons as the internal degrees of freedom and the center-of-mass motion (CM) as the external degrees of freedom of a levitated yttrium iron garnet (YIG) sphere in a cavity-magnomechanical system is studied. Here, we propose a scheme for generating magnon-CM entanglement independent from the mass and size of the sphere in the hybrid magnonic system by driving the magnon with the parametric amplification. First, we show that the power and frequency of the driving field significantly affect this entanglement, since the driving field increases effective magnon-CM coupling. But, by increasing the magnon damping rate, this entanglement considerably decreases. Moreover, in the next step, we demonstrate the manipulation and enhancement of this entanglement by driving the magnon into the squeezed state. Our results present an approach for preparing quantum states and may find promising applications in the quantum metrology and sensing. © 2024 American Physical Society.
Physical Review A (24699934)109(5)
Accurate temperature measurement is critical in many scientific and engineering fields, so that researchers continuously strive to improve the accuracy, sensitivity, and robustness of the current measurement methods. In this paper, we propose a theoretical approach for temperature measurement using an optomechanical system in which the position of a mechanical oscillator is coupled to the cavity field. Our approach enables precise control and manipulation of both, resulting in highly accurate temperature measurements. We evaluate the accuracy of temperature estimation by using classical and quantum Fisher information, considering both open and closed systems, and investigate entanglement effects of the primary field mode. Our findings indicate that increasing entanglement at the input made reduces measurement time and increases sensitivity in estimating the temperature. However, we observe that quantum coherence is destroyed by decoherence, leading to reduced performance of quantum systems. Furthermore, we show that the Fisher information of the system is robust against mechanical decoherence, but significantly damped due to optical decoherence. We discuss the limitations and challenges of our method and suggest possible applications and future directions for our research. Finally, we determine the accuracy of temperature estimation for a typical optomechanical system based on phase values measured in the closed system. Our results demonstrate the potential of optomechanical systems for highly accurate temperature measurement and their robustness against decoherence. This study can provide insights into the field of temperature measurement, offering a theoretical approach that can be applied in many scientific and engineering applications. © 2024 American Physical Society.
