Robust entanglement of an asymmetric quantum dot molecular system in a Josephson junction

We demonstrate how robust entanglement of quantum dot molecular system in a voltage controlled junction can be generated. To improve the quantum information characteristics of this system, we propose an applicable protocol which contains the implementation of asymmetric quantum dots as well as engineering reservoirs. Quantum dots with tunable energy barriers can provide asymmetric coupling coefficients which can be tuned by gap voltages. Also by engineering reservoirs, superconductors can be used as leads in a biased-voltage junction. The high-controllability characteristics of system supplies the arbitrary entanglement by tuning the controlling parameters. Significantly in concurrence-voltage characteristics, perfect entanglement can be achieved in an asymmetric structure and it can be kept with near-unit magnitude in response to bias voltage increasing

Nonclassical properties of a particle in a finite range trap: the f-deformed quantum oscillator approach

A particle bounded in a potential with finite range is described by using an $f$-deformed quantum oscillator approach. Finite range of this potential can be considered as a controllable deformation parameter. The non-classical quantum statistical properties of this deformed oscillator can be manipulated by nonlinearities associated to the finite range

Entanglement between distant atoms mediated by a hybrid quantum system consisting of superconducting flux qubit and resonators

A hybrid quantum system consisting of spatially separated two-level atoms is studied. Two atoms do not interact directly, but they are coupled via an intermediate system which is consisting of a superconducting flux qubit interacting with a mechanical and an electrical resonator which are coupled to one of the atoms. Moreover, the superconducting flux qubit is driven by a classical microwave field. Applying the adiabatic elimination an effective Hamiltonian for the atomic subsystem is obtained. Our results demonstrate that the entanglement degradation decay as well as the fidelity decay in the dispersive regime are faster. Moreover, the driven field amplitude possesses an important role in the entanglement and fidelity evolution

Photon antibunching control in a quantum dot and metallic nanoparticle hybrid system with non-Markovian dynamics

Photon-number statistics of the emitted photons from a quantum dot placed in the vicinity of a metallic nanoparticle (with either shell or solid-sphere geometry) in the non-Markovian regime is investigated theoretically. In the model scheme, the quantum dot is considered as a InAs three- level system in Lambda-type configuration with two transition channels. One of channels is driven by a polarized classical field while the two channels are coupled to the plasmon modes. Plasmon resonance modes of a nanoshell, in contrast of a nanosphere, are tunable at demand frequency by controlling the thickness and the materials of the core and the embedding media. The results reveal that the emitted photons from the hybrid system under consideration are antibunched. Moreover, the anti- bunching behavior of the emitted photons can be controlled by the geometrical parameters of the system, namely, the quantum dot-metal nano particle separation distance, as well as the system's physical parameters including the detuning frequency of the quantum dot transitions with respect to the surface plasmon modes, and the Rabi frequency of the polarized driving field. Additionally, the studied system has the potential to be a highly controllable single-photon source

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

QQ-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

Polaronic Entanglement of Quantum dot Molecule in a voltage-controlled junction

We investigate the influence of vibrational phonon modes on the entanglement through a quantum dot molecule under the bias voltage-driven field. The molecular quantum dot system can be realized by coupled quantum dots in the middle of the suspended carbon nanotube. This system would be described by the Anderson-Holstein model and also can be analyzed by the polaron master equation in Markovian regime. In the presence of electron-phonon interaction, we study the entanglement as a function of bias voltage and temperature. Despite entanglement degradation because of phonon decoherence, we employ an asymmetric coupling protocol to preserve the entanglement in a significant level and also we apply the easy tunable bias voltage driven to engineer its behavior. In dynamics of entanglement, we demonstrate the phenomenon of thermal entanglement degradation and rebirth through the increase of temperature. In this process, thermal entanglement revival is intensively affected by the strength of phonon decoherence. Such that, stronger revival is occurred for higher phonon coupling amount. With an applied time-dependent bias voltage, the entanglement evolution shows periodic revival by time and in response to bias voltage rising, it illustrates decreasing and grows steadily to reach the flat form with considerable magnitude

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 $\Lambda$-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.Comment: 19 page

Generation of entanglement between quantum dot molecule with the presence of phonon effects in a voltage-controlled junction

We investigate the generation of entanglement through a quantum dot molecule under the influence of vibrational phonon modes in a bias voltage junction. The molecular quantum dot system is realized by coupled quantum dots inside a suspended carbon nanotube. We consider the dynamical entanglement as a function of bias voltage and temperature by taking into account the electron-phonon interaction. In order to generate the robust entanglement between quantum dots and preserve it to reach the maximal achievable amount steadily, we introduce an asymmetric coupling protocol and apply the easy tunable bias voltage-driven field. For an oscillating bias voltage, the time-varying entanglement can periodically reach the maximum revival. In thermal entanglement dynamics, the phenomena of thermal entanglement degradation and thermal entanglement revival are observed which are intensively affected by the strength of phonon decoherence. The revival of entanglement shows a larger value for a higher phonon coupling

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