arXiv subjects

B. Askari

Publications and source records attributed to B. Askari.

5 recordsLinked to original sources

arXiv2026

Effect of classical noises on the coherent population trapping based on the Green's function approach to the multiplicative stochastic processes

Inspired by the Green's function (GF) approach in quantum field theory (QFT) and many body physics, we have developed a mathematical formalism to investigate classical multiplicative stochastic processes. Based on this approach, the interacting GF of any dynamical system subjected to classical stochastic noises, which enter into the system equations of motion in a multiplicative way, can be obtained from the noninteracting (free of noise) GF through an infinite perturbative series which may converge to an exact closed form under special conditions. Using this formalism, we have studied the effects of classical noises of the driving laser on the coherent population trapping (CPT) which have a crucial role in the performance of CPT-based atomic clocks. We have shown that if the bandwidth of the colored noise is sufficiently larger than the system damping rate, the infinite series corresponding to the interacting GF can be approximated by the closed form. The presented formalism enables us to investigate all kinds of homogeneous and inhomogeneous broadening mechanisms on the CPT transmission resonance lineshape, including dephasing due to atomic collisions, power/Doppler broadenings, as well as the broadening mechanisms due to phase and amplitude fluctuations of driving laser and compared their destructive effect with each other. It should be emphasized that the presented formalism is applicable to any dynamical system with multiplicative stochastic noises and the CPT phenomenon is just a prototype for the application of the presented formalism in practice.

quant-ph↗

arXiv2025

Investigation of intrinsic nonlinear effects in driven-dissipative optomechanical systems using the generalized linear response theory

In this article, we study the effects of intrinsic nonlinear optomechanical interaction on the linear response of a driven-dissipative optomechanical system to a weak time-dependent perturbation. By calculating the linear response of the cavity optical mode to a weak probe laser in the framework of the generalized linear response theory, it is shown how the Stokes and anti-Stokes sideband amplitudes as well as the power reflection coefficient, and the density of states of the cavity optical mode are expressed in terms of photonic retarded Green's functions. Then, we derive the equations of motion of retarded Green's functions of the system from nonlinear quantum Langevin equations and solve them. It is shown that for a single-photon optomechanical coupling of the order of the cavity linewidth, the nonlinear effect does not manifest itself unless the system satisfies a resonance condition, where the frequency of the upper normal mode of the system is twice that of the lower one. Based on the generality of the present approach which works at all regimes, the validity of linearization approximation is also confirmed at the off-resonance regime.

quant-ph↗

arXiv2023

Frustration of triplet interaction in spin-glass background

Parisi demonstrated in 1979 that pairwise interactions exhibit a glass spin phase when there is disorder. While he discovered an equilibrium solution of the Sherrington-Kirkpatrick (SK) spin-glass model and we know it as a continuous phase transition, the model dedicated to pairwise interactions and higher-order interactions has not been addressed. This research intends to determine whether this phase exists in triplet interactions. Due to the intractable nature of the three interacting spins alone, we employed a perturbation approach to provide an analytical solution for the triplet interactions in the background of the SK spin-glass model. Our results show the existence of this phase in the third-order interaction and a sudden transition that indicates a change in the nature of a glassy spin system transitioning from the continuous order to the first order. It causes a forward shift in the critical temperature by identifying the frustration of triplet interactions.

cond-mat.dis-nn↗

arXiv2021

Dynamics of a hybrid optomechanical system in the framework of the generalized linear response theory

We present a theoretical study of the linear response of a driven-dissipative hybrid optomechanical system consisting of an interacting one-dimensional Bose-Einstein condensate (BEC) to an external time-dependent perturbation in the framework of the generalized linear response theory. Using the equations of motion of the open quantum system Green's function, we obtain the linear responses of the optical and atomic modes of the hybrid system and show how the atom-atom interaction of the BEC atoms affects the two normal resonances of the system as well as the anti-resonance frequency at which the optical field amplitude of the cavity becomes zero. Furthermore, an interpretation of the anti-resonance phenomenon is presented based on the the optical spectral density and the self-energy.

quant-ph↗

arXiv2021

Persistent Homology of Fractional Gaussian Noise

In this paper, we employ the persistent homology (PH) technique to examine the topological properties of fractional Gaussian noise (fGn). We develop the weighted natural visibility graph algorithm, and the associated simplicial complexes through the filtration process are quantified by PH. The evolution of the homology group dimension represented by Betti numbers demonstrates a strong dependency on the Hurst exponent ($H$). The coefficients of the birth and death curve of the $k$-dimensional topological holes ($k$-holes) at a given threshold depend on $H$ which is almost not affected by finite sample size. We show that the distribution function of a lifetime for $k$-holes decays exponentially and the corresponding slope is an increasing function versus $H$, and more interestingly, the sample size effect completely disappears in this quantity. The persistence entropy logarithmically grows with the size of the visibility graph of a system with almost $H$-dependent prefactors. On the contrary, the local statistical features are not able to determine the corresponding Hurst exponent of fGn data, while the moments of eigenvalue distribution ($M_{n}$) for $n\ge1$ reveal a dependency on $H$, containing the sample size effect. Finally, the PH shows the correlated behavior of electroencephalography for both healthy and schizophrenic samples.

physics.data-an↗