arXiv subjects

M. K. Tavassoly

Publications and source records attributed to M. K. Tavassoly.

At least 19 recordsLinked to original sources

arXiv2021

Interaction of a three-level atom Lambda, V, lader with a two-mode field beyond rotating wave approximation: Intermixed intensity-dependent coupling

Recalling that the rotating wave approximation (RWA) is only valid in the weak coupling regimes, the purpose of this paper is to study the Hamiltonian dynamics describing the full quantum mechanical approach of the interaction between various configurations of three-level atoms Lambda, V and ladder distinctly with a two-mode radiation field, while the RWA is not considered; the counter-rotating terms (CRTs) are taken into account. Generally, the presence of CRTs in the Hamiltonian prevents one to achieve an analytical solution. Moreover, as we will show in the present work, using the perturbation theory, analytical solvable Hamiltonians can be successfully obtained. According to our calculations, the contribution of CRTs within the ordinary Hamiltonian is equivalent to the replacement of the constant detuning with a specific intensity dependent detuning in the first order, and the constant atom field coupling with a particular intensity dependent (f deformed) coupling in the second order of the associated perturbation parameter. Moreover, noticing that according to the initial expression of the Hamiltonian, each mode of the field interacts only with a specific pair of the allowed transitions of each type of the three-level atom, it is surprisingly observed that via applying the mentioned approach, the obtained intensity dependent coupling functions depend on both modes of the field, f(na,nb). In this way, it is seen that the CRTs are removed with the price of arriving at some intermixed intensity dependent atom field coupling functions of the two modes of the field. In this way, the obtained final Hamiltonians are analytically solvable. At last, by determining the time evolution of the atom field wave function, we study the effects of CRTs on a few nonclassical properties of the state of the system, including the atomic population inversion and photon statistics.

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arXiv2016

Measuring quasiprobability distribution functions of the cavity field considering field and atomic decays

We study the possibility of reconstructing the quantum state of light in a cavity subject to dissipation. We pass atoms, also subject to decay, through the cavity and surprisingly show that both decays allow the measurement of $s$-parametrized quasiprobability distributions. In fact, if we consider only atomic decay, we show that the Wigner function may be reconstructed. Because these distributions contain whole information of the initial field state, it is possible to recover information after both atomic and field decays occur.

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arXiv2016

Entanglement Swapping Between Dissipative Systems

In this paper, we investigate the possibility of entanglement swapping between two distinct qubits coupled to their own (in general) non-Markovian environments. This is done via Bell state measurement performing on the photons leaving the dissipative cavities. In the continuation, we introduce the concept of entangling power to measure the average of swapped entanglement over all possible pure initial states. Then, we present our results in two strong and weak coupling regimes and discuss the role of detuning parameter in each regime on the amount of swapped entanglement. We also determine the conditions in which the maximum amount of entanglement can be swapped between two qubits. It is revealed that despite of the presence of dissipation, it is possible to create long-living stationary entanglement between two qubits.

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arXiv2016

Quantum Zeno and Anti-Zeno Effects on the Entanglement Dynamics of Qubits Dissipating into a Common and non-Markovian Environment

We investigate the quantum Zeno and anti-Zeno effects on pairwise entanglement dynamics of a collective of non-interacting qubits which have been initially prepared in a Werner state and are off-resonantly coupled to a common and non-Markovian environment. We obtain the analytical expression of the concurrence in the absence and presence of the non-selective measurements. In particular, we express our results in the strong and weak coupling regimes and examine the role of the system size, and the effect of the detuning from the cavity field frequency on the temporal behaviour of the pairwise entanglement. We show that, the detuning parameter has a positive role in the protection of entanglement in the absence of the measurement for weak coupling regime. We find that for the values of detuning parameter less than the cavity damping rate, the quantum Zeno effect is always dominant, while for the values greater than the cavity damping rate, both Zeno and anti-Zeno effects can occur, depending on the measurement intervals. We also find that the anti-Zeno effect can occur in the pairwise entanglement dynamics in the absence and presence of the detuning in the strong coupling regime.

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arXiv2016

Dynamics and Protecting of Entanglement in Two-Level Systems Interacting with a Dissipative Cavity: The Gardiner-Collett Approach

In this paper, we study the exact entanglement dynamics of two two-level atoms in a dissipative cavity. We use the Gardiner-Collett Hamiltonian to model the dissipative cavity, in which, we assume that the two atoms resonantly interact with the cavity field and the cavity field itself interacts with the surrounding medium. Then, with the help of the Fano's technique, we show that, this system can be regarded as two atoms interacting with a heat bath. In such a case, we find that, there exists a decoherence-free state that does not evolve in time. At this time, there exists a so-called super-radiant state which decays in time due to dissipation. At last, we use the quantum Zeno effect to preserve the entanglement which already has been stored in the system.

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arXiv2016

The entangling power of a "glocal" dissipative map

We consider a model of two qubits dissipating into both local and global environments (generally at non-zero temperatures), with the possibility of interpolating between purely local dissipation and purely global one. The corresponding dissipative dynamical map is characterized in terms of its Kraus operators focusing on the stationary regime. We then determine conditions under which entanglement can be induced by the action of such a map. It results (rather counterintuitively) that in order to have entanglement in the presence of local environment, this latter must be at nonzero temperature.

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arXiv2015

Generation and nonclassicality of entangled states via the interaction of two three-level atoms with a quantized cavity field assisted by a driving external classical field

The interaction of two identical three-level atoms of the types $V$, $Ξ$ and $Λ$ with a quantized cavity field as well as a driving external classical field is studied. Under two certain unitary transformations, the system is converted to a typical form of the Jaynes-Cummings model for two three-level atoms. The exact analytical solutions of the wave function for different considered atom-field systems are exactly obtained with the help of the Laplace transform technique, when the atoms are initially prepared in the topmost excited state and the quantized field is in a coherent state. In order to examine the nonclassicality features of the deduced states, the dynamics of the entanglement between subsystems is discussed via two well-known measures, namely, von Neumann entropy of the reduced state and negativity. In addition, we pay attention to the temporal behaviour of quantum statistics of the photons of the field and squeezing phenomenon. Meanwhile, the influence of the external classical field on the latter physical quantities is analyzed in detail. The results show that the mentioned quantities can be sensitively controlled via the external classical field. Also, numerical computations imply the fact that the nonclassicality features in $Ξ$-type three-level atomic system is more visible than the other two configurations. In addition, it is shown that in the particular case of $Λ$-type atomic system, the rank of the reduced density matrix of the three-level atoms is no larger than three, so that negativity fully captures the entanglement of this system and that such entanglement is distillable.

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arXiv2015

Dynamics of different entanglement measures of two three-level atoms interacting nonlinearly with a single-mode field

In this paper, we present a model which exhibits two identical $Ξ$-type three-level atoms interacting with a single-mode field with $k$-photon transition in an optical cavity enclosed by a Kerr medium. Considering full nonlinear formalism, it is assumed that the single-mode field, atom-field coupling and Kerr medium are all $f$-deformed. By using the adiabatic elimination method, it is shown that, the Hamiltonian of the considered system can be reduced to an effective Hamiltonian with two two-level atoms and $f$-deformed Stark shift. In spite of the fact that, the system seems to be complicated, under initial conditions which may be prepared for the atoms (coherent superposition of their ground and upper states) and the field (coherent state), the explicit form of the state vector of the entire system is analytically obtained. Then, the entanglement dynamics between different subsystems (i.e. "field-two atoms", "atom-(field+atom)" and "atom-atom") are evaluated through appropriate measures like von Neumann entropy, tangle and concurrence. In addition, the effects of intensity-dependent coupling, deformed Kerr medium, detuning parameter, deformed Stark shift and multi-photon process on the considered entanglement measures are numerically analyzed, in detail. It is shown that the degree of entanglement between subsystems can be controlled by selecting the evolved parameters, suitably. Briefly, the Kerr medium highly decreases the amount of different considered measures of entanglement, especially for two-photon transition. This destructive effect preserves even when all other parameters are present, too. Furthermore, we find that the so-called entanglement sudden death and birth can occur in the atom-atom entanglement.

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arXiv2014

Entanglement analysis of two-atom nonlinear JCM with nondegenerate two-photon transition, Kerr nonlinearity and two-mode Stark shift

Entangled state, as an essential tool in quantum information processing, may be generated through the interaction between light and matter in cavity quantum electrodynamics. In this paper, we study the interaction between two two-level atoms and a two-mode field in an optical cavity enclosed by a medium with Kerr nonlinearity in the presence of detuning parameter and Stark effect. It is assumed that atom-field coupling and third-order susceptibility of the Kerr medium depend on the intensity of light. In order to investigate the dynamics of the introduced system, we obtain the exact analytical form of the state vector of the considered atom-field system under initial conditions which may be prepared for the atoms (in a coherent superposition of their ground and upper states) and the fields (in standard coherent state). Then, in order to evaluate the degree of entanglement between subsystems, we investigate the dynamics of entanglement through the well-known criteria such as von Neumann reduced entropy, entanglement of formation and negativity. Finally, we analyze the influences of Stark shift, deformed Kerr medium, intensity-dependent coupling and also detuning parameter on the above-mentioned measures, in detail. Numerical results show that the amount of entanglement between different subsystems can be controlled by choosing the evolved parameters, appropriately.

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arXiv2014

Entanglement criteria of two two-level atoms interacting with two coupled modes

In this paper, we study the interaction between two two-level atoms and two coupled modes of a quantized radiation field in the form of parametric frequency converter injecting within an optical cavity enclosed by a medium with Kerr nonlinearity. It is demonstrated that, by applying the Bogoliubov-Valatin canonical transformation, the introduced model is reduced to a well-known form of the generalized Jaynes-Cummings model. Then, under particular initial conditions which may be prepared for the atoms (in a coherent superposition of its ground and upper states) and the fields (in a standard coherent state), the time evolution of state vector of the entire system is analytically evaluated. In order to understand the degree of entanglement between subsystems (atom-field and atom-atom), the dynamics of entanglement through different measures, namely, von Neumann reduced entropy, concurrence and negativity is evaluated. In each case, the effects of Kerr nonlinearity and detuning parameter on the above criteria are numerically analyzed, in detail. It is illustrated that the amount of the degree of entanglement can be tuned by choosing the evolved parameters, appropriately.

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arXiv2014

Algebraic and group treatments to nonlinear displaced number states and their nonclassicality features

Recently, nonlinear displaced number states (NDNSs) have been \emph{manually} introduced, in which the deformation function $f(n)$ has been artificially added to the well-known displaced number states (DNSs). In this paper, after expressing enough physical motivation of our procedure, four distinct classes of NDNSs are presented by applying algebraic and group treatments. To achieve this purpose, by considering the DNSs and recalling the nonlinear coherent states formalism, the NDNSs are logically defined through an algebraic consideration. In addition, by using a particular class of Gilmore-Perelomov-type of $SU(1,1)$ and a class of $SU(2)$ coherent states, the NDNSs are introduced via group theoretical approach. Then, in order to examine the nonclassical behaviour of these states, sub-Poissonian statistics by evaluating Mandel parameter and Wigner quasi-probability distribution function associated with the obtained NDNSs are discussed, in detail.

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arXiv2014

Dynamics of entanglement of a three-level atom in motion interacting with two coupled modes including parametric down conversion

In this paper, a model by which we study the interaction between a motional three-level atom and two-mode field injected simultaneously in a bichromatic cavity is considered; the three-level atom is assumed to be in a $Λ$-type configuration. As a result, the atom-field and the field-field interaction (parametric down conversion) will be appeared. It is shown that, by applying a canonical transformation, the introduced model can be reduced to a well-known form of the generalized Jaynes-Cummings model. Under particular initial conditions, which may be prepared for the atom and the field, the time evolution of state vector of the entire system is analytically evaluated. Then, the dynamics of atom by considering `atomic population inversion' and two different measures of entanglement, i.e., `von Neumann entropy' and `idempotency defect' is discussed, in detail. It is deduced from the numerical results that, the duration and the maximum amount of the considered physical quantities can be suitably tuned by selecting the proper field-mode structure parameter $p$ and the detuning parameters.

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arXiv2014

Nonlinear Quantum Optical Springs and Their Nonclassical Properties

The original idea of quantum optical spring arises from the requirement of quantization of the frequency of oscillations in the Hamiltonian of harmonic oscillator. This purpose is achieved by considering a spring whose constant (and so its frequency) depends on the quantum states of another system. Recently, it is realized that by the assumption of frequency modulation of $ω$ to $ω\sqrt{1+μa^\dagger a}$ the mentioned idea can be established. In the present paper, we generalize the approach of quantum optical spring with particular attention to the {\it dependence of frequency to the intensity of radiation field} that {\it naturally} observes in the {\it nonlinear coherent states}, from which we arrive at a physical system has been called by us as {\it nonlinear quantum optical spring}. Then, after the introduction of the generalized Hamiltonian of nonlinear quantum optical spring and it's solution, we will investigate the nonclassical properties of the obtained states. Specially, typical collapse and revival in the distribution functions and squeezing parameters, as particular quantum features, will be revealed.

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arXiv2014

Quantum entanglement and position-momentum entropic squeezing of a moving Lambda-type three-level atom interacting with a single-mode quantized field with intensity-dependent coupling

In this paper, we study the interaction between a moving $Λ$-type three-level atom and a single-mode cavity field in the presence of intensity-dependent atom-field coupling. After obtaining the state vector of the entire system explicitly, we study the nonclassical features of the system such as quantum entanglement, position-momentum entropic squeezing, quadrature squeezing and sub-Poissonian statistics. According to the obtained numerical results we illustrate that the squeezed period, the duration of entropy squeezing and the maximal squeezing can be controlled by choosing the appropriate nonlinearity function together with entering the atomic motion effect by suitably selection of the field-mode structure parameter. Also, the atomic motion, as well as the nonlinearity function leads to the oscillatory behaviour of the degree of entanglement between the atom and field.

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arXiv2014

Tripartite entanglement dynamics and entropic squeezing of a three-level atom interacting with a bimodal cavity field

In this paper, we study the interaction between a $Λ$-type three-level atom and two quantized electromagnetic fields which are simultaneously injected in a bichromatic cavity surrounded by a Kerr medium in the presence of the field-field interaction (parametric down conversion) and detuning parameters. By applying a canonical transformation, the introduced model is reduced to a well-known form of the generalized Jaynes-Cummings model. Under particular initial conditions which may be prepared for the atom and the field, the time evolution of state vector of the entire system is analytically evaluated. Then, the dynamics of atom is studied through the evolution of the atomic population inversion. In addition, two different measures of entanglement between the tripartite system (three entities make the system: two field modes and one atom) i.e., von Neumann and linear entropy are investigated. Also, two kinds of entropic uncertainty relations, from which entropy squeezing can be obtained, are discussed. In each case, the influences of the detuning parameters and Kerr medium on the above nonclassicality features are analyzed via numerical results, in detail. It is illustrated that the amount of the above-mentioned physical phenomena can be tuned by choosing the evolved parameters, appropriately.

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arXiv2011

Nonclassical properties of coherent states and excited coherent states for continuous spectra

Based on the definition of coherent states for continuous spectra and analogous to photon added coherent states for discrete spectra, we introduce the excited coherent states for continuous spectra. It is shown that, the main axioms of Gazeau-Klauder coherent states will be satisfied, properly. Nonclassical properties and quantum statistics of coherent states, as well as the introduced excited coherent states are discussed. In particular, through the study of quadrature squeezing and amplitude squared squeezing, it will be observed that both classes of the above states can be classified in the intelligent states category.

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arXiv2011

Generalized coherent states for solvable quantum systems with degenerate discrete spectra and their nonclassical properties

In this paper, the generalized coherent state for quantum systems with degenerate spectra is introduced. Then, the nonclassicality features and number-phase entropic uncertainty relation of two particular degenerate quantum systems are studied. Finally, using the Gazeau-Klauder coherent states approach, time evolution of some of the nonclassical properties of the coherent states corresponding to the considered physical systems are discussed.

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arXiv2010

On the non-classicality features of new classes of nonlinear coherent states

In this paper, using an exponential function of intensity of radiation field, two new classes of nonlinear coherent states will be constructed. For the first class, we choose the nonlinearity function as f(n) = exp(βn), where βcharacterizes the strength of the nonlinearity of the quantum system. We show that, the corresponding β-states possess a collection of non-classicality features, only for the particular values of βand z. But, interestingly there exists finite (threshold) values of β, for which all of the non-classicality signs will disappear, in appropriate regions around the origin of the complex plane (z < |Z|). It is then illustrated that, using this threshold (or greater) value of β, the corresponding β-states behave very similar to canonical coherent states, as the most classical quantum states, in approximately whole of the space. In the continuation, we motivate to find another class of nonlinear coherent states, limited to a unit disk centered at the origin, looking like the canonical coherent states in behavior, in exactly the whole range of |z| < 1. This purpose also will be achieved by considering the nonlinearity function as f(n)= exp(λ/n)/\sqrt{n}, where λis a tunable nonlinearity parameter. The canonical coherent state's aspects of the corresponding λ-states will be refreshed, in particular cases, working with a threshold (or greater) value of λ.

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