arXiv subjects

Shishram Rebari

Publications and source records attributed to Shishram Rebari.

5 recordsLinked to original sources

arXiv2026

Role of Asymmetry in the Performance Optimization of a Relativistic Quantum Otto Engine

We present an analytical study of the relativistic quantum Otto cycle driven by a time-dependent harmonic oscillator. By imposing an asymmetry on the two adiabatic processes of this cycle, we obtain distinct scenarios of sudden compression and sudden expansion, and analyze how asymmetry affects the performance of the relativistic quantum Otto engine. By leveraging the Omega function as a unified performance metric, we analytically characterize the efficiency in both scenarios. Our findings demonstrate that the efficiency approaches unity in the sudden compression case, while it is restricted to one-half for the sudden expansion case. Furthermore, we investigate the impact of increasing oscillator velocity on the extracted work and identify parameter regimes where either sudden compression or sudden expansion dominates. Additionally, we examine the optimal operating point using parametric efficiency-work plots, whose loop-shaped structure shows that increasing oscillator velocity enhances both work output and efficiency. Finally, through a detailed phase diagram analysis of the Otto cycle, we observe that the operational region corresponding to the engine mode expands with increasing oscillator velocity, while the refrigeration regime shrinks correspondingly.

quant-ph↗

arXiv2025

Optimal Performance of an Asymmetric Quantum Harmonic Otto Engine and Refrigerator

We study a quantum Otto cycle operating with a time-dependent harmonic oscillator as the working material. We examine the asymmetry present between the two adiabatic processes of the Otto cycle, focusing on cases of sudden expansion and sudden compression. We analytically derive the efficiency and coefficient of performance for an asymmetric Otto cycle, employing the Omega function, which represents the balance between the maximum useful energy and minimum lost energy. Notably, our findings reveal that the efficiency (coefficient of performance) of an asymmetric engine (refrigerator) is higher during the sudden compression case compared to the sudden expansion case. Furthermore, we derive the results for the maximum work efficiency and observe that efficiency at the maximum Omega function consistently exceeds the maximum work efficiency. Finally, we compute the fractional loss of work in both cases to thoroughly examine the performance of asymmetric Otto engine.

quant-ph↗

arXiv2024

Asymmetric Quantum Harmonic Otto Engine Under Hot Squeezed Thermal Reservoir

We study a quantum harmonic Otto engine under a hot squeezed thermal reservoir with asymmetry between the two adiabatic branches introduced by considering different speeds of the driving protocols. In the first configuration, the driving protocol for the expansion stroke is sudden-switch in nature and compression stroke is driven adiabatically, while the second configuration deals with the converse situation. In both cases, we obtain analytic expressions for the upper bound on efficiency and efficiency at optimal work output, which reveals a significant difference between the two configurations. Additionally, we find that the maximum achievable efficiency in sudden expansion case is 1/2 only while it approaches unity for the sudden compression stroke. Further, we study the effect of increasing degree of squeezing on the efficiency and work output of the engine and indicate the optimal operational regime for both configurations under consideration. Finally, by studying the full phase-diagram of the Otto cycle we observe that the operational region of the engine mode grows with increasing squeezing at the expense of refrigeration regime.

quant-ph↗

arXiv2023

Performance analysis of quantum harmonic Otto engine and refrigerator under a trade-off figure of merit

We investigate the optimal performance of quantum Otto engine and refrigeration cycles of a time-dependent harmonic oscillator under a trade-off figure of merit for both adiabatic and nonadiabatic (sudden-switch) frequency modulations. For heat engine (refrigerator), the chosen trade-off figure of merit is an objective function defined by the product of efficiency (coefficient of performance) and work output (cooling load), thus representing a compromise between them. We obtain analytical expressions for the efficiency and coefficient of performance of the harmonic Otto cycle for the optimal performance of the thermal machine in various operational regimes. Particularly, in the sudden-switch regime, we discuss the implications of the nonadiabatic driving on the performance of the thermal machine under consideration, and obtain analytic expressions for the maximum achievable efficiency and coefficient of performance of the harmonic Otto thermal machine. Further, by carrying out a detailed comparative analysis of the heat engine operating under the chosen trade-off objective function with one operating at maximum work output, we show that the trade-off objective functions have desirable operation only for the adiabatic driving whereas for the sudden switch operation, the choice of a trade-off objective function does not make much difference as the performance of the engine is dominated by frictional effects.

quant-ph↗

arXiv2023

Optimization analysis of an endoreversible quantum heat engine with efficient power function

We study the optimal performance of an endoreversible quantum dot heat engine, in which the heat transfer between the system and baths is mediated by qubits, operating under the conditions of a trade-off objective function known as maximum efficient power function defined by the product of power and efficiency of the engine. First, we numerically study the optimization of the efficient power function for the engine under consideration. Then, we obtain some analytic results by applying hightemperature limit and compare the performance of the engine at maximum efficient power functionto the engine operating in the maximum power regime. We find that the engine operating at maximum efficient power function produces at least 88.89% of the maximum power output while at the same time reduces the power loss due to entropy production by considerable amount. We conclude by studying the stochastic simulations of the efficiency of the engine in maximum power and maximum efficient power regime. We find that the engine operating at maximum power is subjected to less power fluctuations as compared to the on one operating at maximum efficient power function.

cond-mat.stat-mech↗