arXiv subjects

M. H. Naderi

Publications and source records attributed to M. H. Naderi.

At least 55 records · Page 3Linked to original sources

arXiv2011

Influence of phonons on exciton-photon interaction and photon statistics of a quantum dot

In this paper, we investigate, phonon effects on the optical properties of a spherical quantum dot. For this purpose, we consider the interaction of a spherical quantum dot with classical and quantum fields while the exciton of quantum dot interacts with a solid state reservoir. We show that phonons strongly affect the Rabi oscillations and optical coherence on first picoseconds of dynamics. We consider the quantum statistics of emitted photons by quantum dot and we show that these photons are anti-bunched and obey the sub-Poissonian statistics. In addition, we examine the effects of detuning and interaction of quantum dot with the cavity mode on optical coherence of energy levels. The effects of detuning and interaction of quantum dot with cavity mode on optical coherence of energy levels are compared to the effects of its interaction with classical pulse.

quant-ph↗

arXiv2011

Steady-state entanglement and normal-mode splitting in an atom-assisted optomechanical system with intensity-dependent coupling

In this paper, we study theoretically the bipartite and tripartite continuous variable entanglement as well as the normal-mode splitting in a single-atom cavity optomechanical system with intensity-dependent coupling. The system under consideration is formed by a Fabry-Perot cavity with a thin vibrating end mirror and a two-level atom in the Gaussian standing-wave of the cavity mode. We first derive the general form of Hamiltonian describing the tripartite intensity-dependent atom-field-mirror coupling due to the presence of cavity mode structure. We then restrict our treatment to the first vibrational sideband of the mechanical resonator and derive a novel form of tripartite atom-field-mirror Hamiltonian. We show that when the optical cavity is intensely driven one can generate bipartite entanglement between any pair of the tripartite system, and that, due to entanglement sharing, the atom-mirror entanglement is efficiently generated at the expense of optical-mechanical and optical-atom entanglement. We also find that in such a system, when the Lamb-Dicke parameter is large enough one can simultaneously observe the normal mode splitting into three modes.

quant-ph↗

arXiv2011

Nonlinear coherent state of an exciton in a wide quantum dot

In this paper, we derive the dynamical algebra of a particle confined in an infinite spherical well by using the $f$-deformed oscillator approach. We consider an exciton with definite angular momentum in a wide quantum dot interacting with two laser beams. We show that under the weak confinement condition, and quantization of the center-of-mass motion of exciton, the stationary state of it can be considered as a special kind of nonlinear coherent states which exhibits the quadrature squeezing.

quant-ph↗

arXiv2011

$Q$-deformed description of excitons and associated physical results

We consider excitons in a quantum dot as q-deformed systems. Interaction of some excitonic systems with one cavity mode is considered. Dynamics of the system is obtained by diagonalizing total Hamiltonian and emission spectrum of quantum dot is derived. Physical consequences of q-deformed exciton on emission spectrum of quantum dot is given. It is shown that when the exciton system deviates from Bose statistics, emission spectra will become multi peak. With our investigation we try to find the origin of the q-deformation of exciton. The optical response of excitons, which affected by the nonlinear nature of q-deformed systems, up to the second order of approximation is calculated and absorption spectra of the system is given.

quant-ph↗

arXiv2011

Back-action ground state cooling of a micromechanical membrane via intensity-dependent interaction

We propose a theoretical scheme to show the possibility of achieving the quantum ground state cooling of a vibrating micromechanical membrane inside a high finesse optical cavity by back-action cooling approach. The scheme is based on an intensity-dependent coupling of the membrane to the intracavity radiation pressure field. We find the exact expression for the position and momentum variances of the membrane by solving the linearized quantum Langevin equations in the steady-state, conditioned by the Routh-Hurwitz criterion. We show that by varying the Lamb-Dicke parameter and the membrane's reflectivity one can effectively control the mean number of excitations of vibration of the membrane and also cool down the system to micro-Kelvin temperatures.

quant-ph↗

arXiv2011

Generation of motional nonlinear coherent states and their superpositions via intensity-dependent coupling of a cavity field to a micromechanical membrane

We propose a theoretical scheme to show the possibility of generating motional nonlinear coherent states and their superposition for an undamped vibrating micromechanical membrane inside an optical cavity. The scheme is based on an intensity-dependent coupling of the membrane to the radiation pressure field. We show that if the cavity field is initially prepared in a Fock state, the motional state of the membrane may evolve from vacuum state to a special type of nonlinear coherent states. By examining the nonclassical properties of the generated state of the membrane, including the quadrature squeezing and the sub-Poissonian statistics, we find that by varying the Lamb-Dicke parameter and the membrane's reflectivity one can effectively control those properties. In addition, the scheme offers the possibility of generating various types of the so-called nonlinear multicomponent Schrodinger cat sates of the membrane. We also examine the effect of the damping of the cavity field on the motional state of the membrane.

quant-ph↗

arXiv2010

Dynamical Behaviours of the Nonlinear Atom-Field Interaction in the Presence of Classical Gravity: f-Deformation Approach

In this paper, we investigate the effects of a classical gravitational field on the dynamical behaviour of nonlinear atom-field interaction within the framework of the f-deformed Jaynes-Cummings model. For this purpose, we first introduce a set of new atomic operators obeying an f-deformed su(2) algebraic structure to derive an effective Hamiltonian for the system under consideration. Then by solving the Schrodinger equation in the interaction picture and considering certain initial quantum states for the atomic and radiation subsystems, we analyze the influence of gravity on the temporal evolution of the atomic population inversion, atomic dipole squeezing, atomic momentum diffusion, photon counting statistics, and deformed quadrature squeezing of the radiation field.

quant-ph↗

arXiv2008

Influence of atomic collisions on spectrum of light scattered from an f-deformed Bose-Einstein condensate

In this paper, we investigate the spectrum of light scattered from a Bose-Einstein condensate in the framework of f-deformed boson. We use an f-deformed quantum model in which the Gardiners phonon operators for BEC are deformed by an operator-valued function, f(n), of the particle-number operator n. We consider the collisions between the atoms as a special kind of f-deformation. The collision rate k is regarded as the deformation parameter and the spectrum of light scattered from the deformed BEC is analyzed. In particular, we find that with increasing the values of deformation parameters k and eta=1/N (N, total number of condensate atoms) the scattering spectrum shows deviation from the spectrum associated with nondeformed Bose-Einstein condensate.

quant-ph↗

arXiv2008

Controlling subluminal to superluminal behavior of group velocity in an f-deformed Bose-Einstein condensate beyond the rotating wave approximation

In this paper, we investigate tunable control of the group velocity of a weak probe field propagating through an f-deformed Bose-Einstein condensate of three-level atoms beyond the rotating wave approximation. For this purpose, we use an f- deformed generalization of an effective two-level quantum model of the three-level configuration without the rotating wave approximation in which the Gardiners phonon operators for Bose-Einstein condensate are deformed by an operator- valued function,f(n), of the particle- number operator n . Corrections produced by the counter- rotating terms appear in the first order as an intensity- dependent detuning and in the second order as an intensity- dependent atom-field coupling. We consider the collisions between the atoms as a special kind of f- deformation where the collision rate k is regarded as the deformation parameter. We demonstrate the enhanced effect of subluminal and superluminal propagation based on electromagnetically induced transparency and electromagnetically induced absorption, respectively. In particular, we find that (i) the absorptive and dispersive properties of the deformed condensate can be controlled effectively in the absence of the rotating wave approximation by changing the deformation parameter k, the total number of atoms N and the counter- rotating terms parameter, (ii) by increasing the values of k, 1/N and the counter- rotating terms parameter, the group velocity of the probe pulse changes, from subluminal to superluminal and (iii) beyond the rotating wave approximation, the subluminal and superluminal behaviors of the probe field are enhanced.

quant-ph↗

arXiv2008

Subluminal to superluminal propagation of an optical pulse in an f-deformed Bose- Einstein condensate

In this paper, we investigate the propagation of a weak optical probe pulse in an f-deformed Bose- Einstein condensate (BEC) of a gas with the -type three- level atoms in the electromagnetically induced transparency (EIT) regime. We use an f- deformed generalization of an effective two- level quantum model of the three- level configuration in which the Gardiner phonon operators for BEC are deformed by an operator- valued function, f(n), of the particle- number operator n. With making use of the quantum approach of the angular momentum theory we obtain the eigenvalues and eigenfunctions of the system up to first order approximation. We consider the collisions between the atoms as a special kind of f- deformation. The collision rate k is regarded as the deformation parameter and light propagation in the deformed BEC is analyzed. In particular, we show that the absorptive and dispersive properties of the deformed condensate can be controlled effectively by changing the deformation parameter k and the total number of atoms. We find that by increasing the value of k the group velocity of the probe pulse changes, through deformed condensate, from subluminal to superluminal.

quant-ph↗

arXiv2007

Effects of a classical homogeneous gravitational field on the cavity-field entropy and generation of the Schrodinger-cat states in the Jaynes-Cummings model

In this paper, we examine the effects of the gravitational field on the dynamical evolution of the cavity-field entropy and the creation of the Schrodinger-cat state in the Jaynes-Cummings model. We consider a moving two-level atom interacting with a single mode quantized cavity-field in the presence of a classical homogeneous gravitational field. Based on an su(2) algebra, as the dynamical symmetry group of the model, we derive the reduced density operator of the cavity-field which includes the effects of the atomic motion and the gravitational field. Also, we obtain the exact solution and the approximate solution for the system-state vector, and examine the atomic dynamics. By considering the temporal evolution of the cavity-field entropy as well as the dynamics of the Q-function of the cavity-field we study the effects of the gravitational field on the generation of the Schrodinger-cat states of the cavity-field by using the Q-function, field entropy and approximate solution for the system-state vector. The results show that the gravitational field destroys the generation of the Schrodinger-cat state of the cavity-field.

quant-ph↗

arXiv2007

Dissipative dynamics of the semiconductor-cavity QED with q-deformed bosons in the dispersive approximation

In this paper we give fully analytical description of the dynamics of a collection of $N$-Frenkel excitons in high density regime dispersively coupled to a single mode cavity field, in the presence of both exciton and cavity-field dissipations. By using excitonic operators as q-deformed bosonic operators for the system, we solve analytically the Liouville equation for the density operator at zero temperature and investigate the influence of the number of excitons and the effect of both dissipations on dynamical behavior of the system. We use the solution of master equation to explore the dissipative dynamics of non-classical properties such as, molecule-field entanglement, quadrature squeezing of the field, and molecular dipole squeezing. We find that the non-classical properties are strongly affected by the number of excitons and also by the existence of both dissipations.

quant-ph↗

arXiv2007

Spatial confinement effects on quantum field theory using nonlinear coherent states approach

We study some basic quantum confinement effects through investigation a deformed harmonic oscillator algebra. We show that spatial confinement effects on a quantum harmonic oscillator can be represented by a deformation function within the framework of nonlinear coherent states theory. Using the deformed algebra, we construct a quantum field theory in confined space. In particular, we find that the confinement influences on some physical properties of the electromagnetic field and it gives rise to nonlinear interaction. Furthermore, we propose a physical scheme to generate the nonlinear coherent states associated with the electromagnetic field in a confined region.

quant-ph↗

arXiv2007

Quantum statistical properties of the Jaynes-Cummings model in the presence of a classical homogeneous gravitational field

The temporal evolution of quantum statistical properties of an interacting atom-radiation field system in the presence of a classical homogeneous gravitational field is investigated within the framework of the Jaynes-Cummings model. To analyse the dynamical evolution of the atom-radiation system a quantum treatment of the internal and external dynamics of the atom is presented based on an alternative su(2) dynamical algebraic structure. By solving the Schrödinger equation in the interaction picture, the evolving state of the system is found by which the influence of the gravitational field on the dynamical behavior of the atom-radiation system is explored. Assuming that initially the radiation field is prepared in a coherent state and the two-level atom is in a coherent superposition of the excited and ground states, the influence of gravity on the collapses and revivals of the atomic population inversion, atomic dipole squeezing, atomic momentum diffusion, photon counting statistics and quadrature squeezing of the radiation field is studied.

quant-ph↗

arXiv2007

Influence of a classical homogeneous gravitational field on dissipative dynamics of the Jaynes-Cummings model with phase damping

In this paper, we study the dissipative dynamics of the Jaynes-Cummings model with phase damping in the presence of a classical homogeneous gravitational field. The model consists of a moving two-level atom simultaneously exposed to the gravitational field and a single-mode traveling radiation field in the presence of the phase damping. We present a quantum treatment of the internal and external dynamics of the atom based on an alternative su(2) dynamical algebraic structure. By making use of the super-operator technique, we obtain the solution of the master equation for the density operator of the quantum system, under the Markovian approximation. Assuming that initially the radiation field is prepared in a Glauber coherent state and the two-level atom is in the excited state, we investigate the influence of gravity on the temporal evolution of collapses and revivals of the atomic population inversion, atomic dipole squeezing, atomic momentum diffusion, photon counting statistics and quadrature squeezing of the radiation field in the presence of phase damping.

quant-ph↗

arXiv2006

Influence of gravitational field on quantum-nondemolition measurement of atomic momentum in the dispersive Jaynes-Cummings model

We present a theoretical scheme based on su(2) algebra to investigate the influence of homogeneous gravitational field on the quantum nondemolition measurement of atomic momentum in dispersive Jaynes-Cummings model. In the dispersive Jaynes-Cummings model, when detuning is large and the atomic motion is in a propagating light wave, we consider a two-level atom with quantized cavity-field in the presence of a homogeneous gravitational field. We derive an effective Hamiltonian describing the dispersive atom-field interaction in the presence of gravitational field. We can see gravitational influence both on the momentum filter and momentum distribution. Moreover, gravitational field decreases both tooth spacing of momentum and the width of teeth of momentum.

physics.atom-ph↗

arXiv2006

Geometric approach to nonlinear coherent states using the Higgs model for harmonic oscillator

In this paper, we investigate the relation between the curvature of the physical space and the deformation function of the deformed oscillator algebra using non-linear coherent states approach. For this purpose, we study two-dimensional harmonic oscillators on the flat surface and on a sphere by applying the Higgs modell. With the use of their algebras, we show that the two-dimensional oscillator algebra on a surface can be considered as a deformed one-dimensional oscillator algebra where the effect of the curvature of the surface is appeared as a deformation function. We also show that the curvature of the physical space plays the role of deformation parameter. Then we construct the associated coherent states on the flat surface and on a sphere and compare their quantum statistical properties, including quadrature squeezing and antibunching effect.

quant-ph↗

arXiv2004

Generation of nonlinear coherent states in a coherently pumped micromaser under intensity-dependent Jaynes-Cummings model

In this paper the possibility of generating nonlinear coherent states of the radiation field in a micromaser is explored. It is shown that these states can be provided in a lossless micromaser cavity under the weak Jaynes-Cummings interaction with intensity-dependent coupling of large number of individually injected two-level atoms in a coherent superposition of the upper and lower states. In particular, we show that the so-called nonlinear squeezed vacuum and nonlinear squeezed first excited states, as well as the even and odd nonlinear coherent states can be generated in the presence of two-photon transitions.

quant-ph↗