arXiv subjects

Ali Mahdifar

Publications and source records attributed to Ali Mahdifar.

14 recordsLinked to original sources

arXiv2025

Curvature-Induced Nonclassicality in a Generalized Jaynes-Cummings Model

In this paper, we investigate the influence of spatial curvature on the Jaynes-Cummings model. We employ an analog model of general relativity, representing the field inside a cavity using oscillators arranged in a circle instead of a straight line, where increasing curvature corresponds to a smaller circle radius. We investigate the nonclassical features of this quantum system arising from the interaction between a two-level atom and a deformed harmonic oscillator on a circle, which serves as curved-space counterpart to the flat oscillator. We analyze the time evolution of atom-field states and, based on this dynamic, examine how spatial curvature influences the Mandel parameter, entropy, and the behavior of the Wigner distribution function. Our results demonstrate that the spatial curvature plays critical roles in controlling these nonclassical properties.

quant-ph↗

arXiv2025

Effects of Spatial Curvature on Blackbody Radiation: Modifications to Energy Distribution and Fundamental Laws

In this paper, we investigate the effects of spatial curvature on blackbody radiation. By employing an analog model of general relativity, we replace the conventional straight-line harmonic oscillators used to model blackbody radiation with oscillators on a circle. This innovative approach provides an effective framework for describing blackbody radiation influenced by spatial curvature. We derive the curvature-dependent Planck energy distribution and find that moving from flat to curved space results in a reduction in both the height and width of the Planck function. Moreover, increasing the curvature leads to a pronounced redshift in the peak frequency. We also analyze the influence of spatial curvature on the Stefan-Boltzmann law, Rayleigh-Jeans law, and Wien law.

gr-qc↗

arXiv2024

Curvature effects on stimulated parametric down-conversion process: an analog model

In this paper, we utilize an analog model of the general relativity and investigate the influence of spatial curvature on quantum properties of stimulated parametric down-conversion process. For this purpose, we use two-mode sphere coherent state as the input beams of the aforementioned process. These states are realization of coherent states of two-dimensional harmonic oscillator, which lies on a two-dimension sphere. We calculate the entanglement of output states of stimulated parametric down conversion process, measured by linear entropy, and show that it depends on the spatial curvature. So, by preparing the suitable two-mode sphere coherent states, it is possible to control the entanglement between the output states in the laboratory. In addition, we consider mean number and Mandel parameter of the output states of the process and also, their cross-correlation function, as the convince measures of non-classical behaviors.

quant-ph↗

arXiv2021

Coherent states on a circle: the Higgs-like approach

In this paper, the Higgs-like approach is used to analyze the quantum dynamics of a harmonic oscillator constrained on a circle. We obtain the Hamiltonian of this system as a function of the Cartesian coordinate of the tangent line through the gnomonic projection and then quantize it in the standard way. We then recast the Hamiltonian in a shape-invariant form and derive the spectrum energy of the confined harmonic oscillator on the circle. With help of the f-deformed oscillator algebra, we construct the coherent states on the circle and investigate their quantum statistical properties. We find that such states show nonclassical features like squeezing and sub-Poissonian statistics even in small curvatures of the circle.

quant-ph↗

arXiv2021

Nonlinear optical effects on the atom-field interaction based on the nonlinear coherent states approach

In this paper, to study the effects of a nonlinear medium on the atom-field interaction, we use the nonlinear coherent states approach. For this purpose, we choose the two-mode cross-Kerr as the our nonlinear optical phenomena and with the use of it's algebra, we show that it can be described equivalently by a deformed oscillator algebra and also, by a deformed (su(2)) algebra. Then, we construct the associated coherent states and investigate their statistical properties. After that, as an example of applicability of the constructed two-mode nonlinear coherent states, we investigate the nonlinear effects of the medium on the dynamics of atom-field interaction within the framework of the coherent states. By using the time-dependent Schrödinger equation, we first obtain the atom-field state and then study the effect of the nonlinear medium on the occupation probabilities of the atomic levels. In the following, we consider the relation between the revival time of the atomic occupation probabilities and the nonlinear parameter of the medium. Then, to study the nonlinear effects on the dynamical properties of the cavity field, we consider photon distribution, correlation function, Mandel parameters of the field, the von Neumann entropy and the squeezing. Particularly, the nonlinearity of the media on the nonclassical properties of two modes is clarified.

quant-ph↗

arXiv2020

Nonlinear Coherent States of the Fokas-Lagerstrom Potential

In this paper, we introduce an algebraic approach to construct Fokas-Lagerstrom coherent states. To do so, we define deformed creation and annihilation operators associated to this system and investigate their algebra. We show that these operators satisfy the $f$-deformed Weyl-Heisenberg algebra. Then, we propose a theoretical scheme to generate the aforementioned coherent states. The present contribution shows that the Fokas-Lagerstrom nonlinear coherent states possess some non-classical features.

quant-ph↗

arXiv2019

Quantum light propagation in a uniformly moving dissipative slab

Within the framework of a phenomenological quantization scheme, we present the quantization of the electromagnetic field in the presence of a moving absorptive and dispersive magneto-dielectric slab (MDS) with uniform velocity in the direction parallel to its interface. We derive the quantum input-output relations for the case that quantum states propagate perpendicularly to the moving MDS.We thoroughly investigate the impact of the motion of the movingMDS on quantum properties of the incident states. To illustrate this, by modeling the dispersive and dissipative effects of the slab by the Lorentz model in its rest frame, we compute the quadrature squeezing and the Mandel parameter for the transmitted state when the incident states from left and right sides are, respectively, the coherent and the quantum vacuum states. It is shown that how quantum features of the incident state are degraded when it is transmitted through the moving MDS.

quant-ph↗

arXiv2018

Free particle and isotropic harmonic oscillator on a spheroidal surface: the Higgs-like approach

In this paper, we investigate the dynamics of both free particle and isotropic harmonic oscillator constrained to move on a spheroidal surface using two consecutive projections: a projection onto a sphere surface followed by the gnomonic projection onto a tangent plane to the spheroid. We obtain the Hamiltonian of the aforementioned systems in terms of the Cartesian coordinates of the tangent plane and then quantize it in the standard way. It is shown that the effect of non-sphericity of the surface can be treated as the appearance of an effective potential. By using the perturbation theory up to the first order in second eccentricity of the spheroid, we approximately calculate the eigenfunctions and eigenvalues of the free particle, as well as the isotropic harmonic oscillator on the spheroidal surface. We find that the deviation from the sphericity plays an important role in splitting the energy levels of the isotropic oscillator on a sphere, and lifting the degeneracy.

quant-ph↗

arXiv2018

Spontaneous emission of a moving atom in the presence of magnetodielectric material: A relativistic approach

In this paper, based on a canonical quantization scheme, we study the effect of the relativistic motion of an excited atom on its decay rate in the presence of absorbing and dispersive media. For this purpose, we introduce an appropriate Lagrangian and describe the center-of-mass dynamical variables by the Dirac field. We obtain the Hamiltonian of the system in a multipolar form and calculate the motion equations of the system in the Schrödinger picture. We find that the decay rate and the quantum electrodynamics level shift of the moving atom can be expressed in terms of the imaginary part of the classical Green tensor and the center-of-mass velocity of the atom.

quant-ph↗

arXiv2018

Photon-added and photon-subtracted coherent states on a sphere

In this paper, we construct the $m$-photon-added and $m$-photon-subtracted coherent states on a sphere. These states are shown to satisfy the usual conditions of continuity in the label, normalizability and the resolution of identity. The preparation of the constructed states, as the states of radiation field is considered. We examine and analyze the nonclassical properties of these states, including the photon mean number, Mandel parameter and quadrature squeezing. We find that these states are sub-Poissonian in nature, whereas the degree of squeezing is reduced (enhanced) by increasing $m$ for the photon-added (photon-subtracted) coherent states on a sphere.

quant-ph↗

arXiv2017

Scattering of nonlinear coherent state on sphere by an absorptive and dispersive dielectric slab

In this paper, we examine the modification of specific nonclassical properties of the nonlinear coherent state on sphere upon perpendicular propagation through an absorptive and dispersive dielectric slab at finite temperature. For this purpose, by describing the dielectric dispersion of the slab by Lorentz model, the quadrature squeezing and the Mandel parameter are evaluated for the transmitted state. A generalization of single-mode nonlinear coherent state to the continuum-mode is considered. The degree of second-order coherence is instead calculated for a continuum nonlinear coherent state on sphere, and the quantum noise effects produced by transmission through the slab on the antibunching feature are examined. We find that near the medium resonance the detrimental effect of the loss and thermal fluctuations of the slab are not compensate with increasing the physical space curvature of the incident state.

quant-ph↗

arXiv2016

Spontaneous emission and the operation of invisibility cloaks: Can the invisibility cloaks render objects invisible in quantum mechanic domain?

As a probe to explore the ability of invisibility cloaks to conceal objects in the quantum mechanics domain, we study the spontaneous emission rate of an excited two-level atom in the vicinity of an ideal invisibility cloaking. On this base, first, a canonical quantization scheme is presented for the electromagnetic field interacting with atomic systems in an anisotropic, inhomogeneous and absorbing magnetodielectric medium which can suitably be used for studying the influence of arbitrary invisibility cloak on the atomic radiative properties. The time dependence of the atomic subsystem is obtained in the Schrodinger picture. By introducing a modified set of the spherical wave vector functions, the Green tensor of the system is calculated via the continuous and discrete methods. In this formalism, the decay rate and as well the emission pattern of the aforementioned atom are computed analytically for both weak and strong coupling interaction, and then numerically calculations are done to demonstrate the performances of cloaking in the quantum mechanics domain. Special attention is paid to different possible orientations and locations of atomic system near the spherical invisibility cloaking. Results in the presence and the absence of the invisibility cloak are compared. We find that the cloak works very well far from its resonance frequency to conceal a macroscopic object, whereas at near the resonance frequency the object is more visible than the situation that the object is not covered by the cloak.

quant-ph↗

arXiv2015

Quantum dissipative Higgs model

By using a continuum of oscillators as a reservoir, we present a classical and a quantum-mechanical treatment for the Higgs model in the presence of dissipation. In this base, a fully canonical approach is used to quantize the damped particle on a spherical surface under the action of a conservative central force, the conjugate momentum is defined and the Hamiltonian is derived. The equations of motion for the canonical variables and in turn the Langevin equation are obtained. It is shown that the dynamics of the dissipative Higgs model is not only determined by a projected susceptibility tensor that obeys the Kramers-Kronig relations and a noise operator but also the curvature of the spherical space. Due to the gnomonic projection from the spherical space to the tangent plane, the projected susceptibility displays anisotropic character in the tangent plane. To illuminate the effect of dissipation on the Higgs model, the transition rate between energy levels of the particle on the sphere is calculated. It is seen that appreciable probabilities for transition are possible only if the transition and reservoir's oscillators frequencies to be nearly on resonance.

quant-ph↗

arXiv2012

Two Dimensional Isotropic Harmonic Oscillator on a Time-dependent Sphere

In this paper, we investigate a two dimensional isotropic harmonic oscillator on a time-dependent spherical background. The effect of the background can be represented as a minimally coupled field to the oscillator's Hamiltonian. For a fluctuating background, transition probabilities per unit time are obtained. Transitions are possible if the energy eigenvalues of the oscillator $E_i$ and frequencies of the fluctuating background $ω_n$ satisfy the following two simple relations: $E_{j}\simeq E_{i}-\hbarω_{n}$ (stimulated emission) or $E_{j}\simeq E_{i}+\hbarω_{n}$ (absorption). This indicates that a background fluctuating at a frequency of $ω_n$ interacts with the oscillator as a quantum field of the same frequency. We believe this result is also applicable for an arbitrary quantum system defined on a fluctuating maximally symmetric background.

quant-ph↗