arXiv subjects

Narges Cheraghpour

Publications and source records attributed to Narges Cheraghpour.

3 recordsLinked to original sources

arXiv2025

The Mpemba effect in quantum oscillating and two-level systems

The Empemba effect (ME) is investigated in the context of ubiquitous quantum oscillating and two-level systems (TLS) using a novel approach (DOI 10.1088/1402-4896/ad97f1). Exact reduced density matrices for various initial states are derived. The temporal behavior of the trace distance for these initial states is calculated analytically and presented. For a dissipative quantum oscillating system, it is demonstrated that number states $|N\rangle$ intersect with coherent states $|α\rangle$, with this intersection occurring earlier for smaller values of $N$. Additionally, thermal states intersect with coherent states for specific values of $|α|$, leading to the occurrence of the ME in these two scenarios. A weaker version of the ME is also observed for thermal and number states. In the case of a quantum TLS, it is shown that the ME effect occurs, and the potential for its realization and experimental observation is discussed, with reference to the Jaynes-Cummings model (JCM) involving a decaying time-dependent coupling function.

quant-ph↗

arXiv2025

Quantum dynamics of a bosonic mode and a two-level system interacting with several reservoirs

In the framework of a novel dissipative scheme, we have investigated the quantum dynamics of an oscillating system interacting with two reservoirs with different temperatures trough different time-dependent coupling functions. The reduced density matrix, quantum optical characteristic functions, and (quasi) distribution functions like Husimi, Glauber-Sudarshan and Wigner functions on the phase space of the oscillator are obtained. The problem has been generalized to the case where the oscillator is interacting with $n$ distinctive reservoirs, and a quantum current and an effective reservoir is introduced. Finally, the quantum dynamics of a two-level system interacting with two reservoirs has been investigated, and the exact reduced density matrix is obtained.

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arXiv2024

A novel scheme for modelling dissipation or thermalization in open quantum systems

In this letter, we introduce a novel method for investigating dissipation (gain) and thermalization in an open quantum system. In this method, the quantum system is coupled linearly with a copy of itself or with another system described by a finite number of bosonic operators. The time-dependent coupling functions play a fundamental role in this scheme. To demonstrate the efficiency and significance of the method, we apply it to some ubiquitous open quantum systems. Firstly, we investigate a quantum oscillator in the presence of a thermal bath at the inverse temperature $β$, obtaining the reduced density matrix, the Husimi distribution function, and the quantum heat distribution function accurately. The results are consistent with existing literature by appropriate choices for the time-dependent coupling function. To illustrate the generalizability of this method to systems interacting with multiple thermal baths, we study the interaction of a quantum oscillator with two thermal baths at different temperatures and obtain compatible results. Subsequently, we analyze a two-level atom with energy or phase dissipation and derive the spontaneous emission and the pure dephasing processes consistently using the new method. Finally, we investigate the Markovianity in a dissipative two-level system.

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