A. P. Alodjants

Nonlinear properties and stabilities of polaritonic crystals beyond the low-excitation-density limit

Coherent properties of a two-dimensional spatially periodic structure, polaritonic crystal (PolC) formed by trapped two-level atoms in an optical cavity array interacting with a light field, are analyzed. By considering the wave function overlapping for both photonic and atomic states, a cubic-quintic complex nonlinear Schr¨ odinger equation is derived for the dynamics of coupled atom-light states, wave function of low-branch polaritons, associated with PolC in the continuous limit. A variational approach predicts that a stable ground-state wave function of PolC exists but is accompanied by an oscillating width. For a negative scattering length, the wave function collapses in the presence of a small quintic nonlinearity appearing due to a three-body polariton interaction. By studying the nonequilibrium (dissipative) dynamics of polaritons with adiabatic approximation, we have shown that the collapse of PolC wave function can be prevented even in the presence of small decaying of a number of polariton particles. DOI: 10.1103/PhysRevA.84.013813

Hyperbolic Metamaterials with Bragg Polaritons.

We propose a novel mechanism for designing quantum hyperbolic metamaterials with the use of semiconductor Bragg mirrors containing periodically arranged quantum wells. The hyperbolic dispersion of exciton-polariton modes is realized near the top of the first allowed photonic miniband in such a structure which leads to the formation of exciton-polariton X waves. Exciton-light coupling provides a resonant nonlinearity which leads to nontrivial topologic solutions. We predict the formation of low amplitude spatially localized oscillatory structures: oscillons described by kink shaped solutions of the effective Ginzburg-Landau-Higgs equation. The oscillons have direct analogies in gravitational theory. We discuss implementation of exciton-polariton Higgs fields for the Schrödinger cat state generation.

Solitons in cavity-QED arrays containing interacting qubits

(Dated: August 1, 2012)We reveal the existence of polariton soliton solutions in the array of weakly coupled optical cavities,each containing an ensemble of interacting qubits. An effective complex Ginzburg-Landau equationis derived in the continuum limit taking into account the effects of cavity field dissipation and qubitdephasing. We have shown that an enhancement of the induced nonlinearity can be achieved by twoorder of the magnitude with a negative interaction strength which implies a large negative qubit-fielddetuning as well. Bright solitons are found to be supported under perturbations only in the upper(optical) branch of polaritons, for which the corresponding group velocity is controlled by tuningthe interacting strength. With the help of perturbation theory for solitons, we also demonstratethat the group velocity of these polariton solitons is suppressed by the diffusion process.I. INTRODUCTION

Permanent Rabi oscillations in coupled exciton-photon systems with PT -symmetry

We propose a physical mechanism which enables permanent Rabi oscillations in driven-dissipative condensates of exciton-polaritons in semiconductor microcavities subjected to external magnetic fields. The method is based on stimulated scattering of excitons from the incoherent reservoir. We demonstrate that permanent non-decaying oscillations may appear due to the parity-time symmetry of the coupled exciton-photon system realized in a specific regime of pumping to the exciton state and depletion of the reservoir. At non-zero exciton-photon detuning, robust permanent Rabi oscillations occur with unequal amplitudes of exciton and photon components. Our predictions pave way to realization of integrated circuits based on exciton-polariton Rabi oscillators.

Thermalization of coupled atom-light states in the presence of optical collisions

The interaction of a two-level atomic ensemble with a quantized single-mode electromagnetic field in the presence of optical collisions is investigated both theoretically and experimentally. The main focus is on achieving thermal equilibrium for coupled atom-light states (in particular dressed states). We propose a model of atomic dressed-state thermalization that accounts for the evolution of the pseudo-spin Bloch vector components and characterize the essential role of the spontaneous emission rate in the thermalization process. Our model shows that the time of thermalization of the coupled atom-light states depends strictly on the ratio of the detuning to the resonant Rabi frequency. The predicted time of thermalization is in the nanosecond domain at full optical power and about 10 times shorter than the natural lifetime in our experiment. Experimentally we investigate the interaction of the optical field with rubidium atoms in an ultrahigh-pressure buffer gas cell under the conditions of large atom-field detuning comparable to the thermal energy in frequency units. In particular, an observed asymmetry of the saturated lineshape is interpreted as evidence of thermal equilibrium of coupled atom-light states.

Tunneling-assisted optical information storage with lattice polariton solitons in cavity-QED arrays

Considering two-level media in the array of weakly coupled nano-cavities, we reveal a variety of dynamical regimes, such as diffusion, self-trapping, soliton, and breathers for the wave-packets in the presence of photon tunneling processes between the next-nearest cavities. We focus our attention on the low branch (LB) bright polariton soliton formation, due to the two-body polariton-polariton scattering processes. When detuning frequency is manipulated adiabatically, the low-branch lattice polariton localized states, i.e., that are solitons and breathers evolving between photon-like and matter-like states, are shown to act as carriers for spatially distributed storage and retrieval of optical information.

Generation of Nonclassical States of Light in the Bose-Einstein Condensate under Electromagnetically Induced Transparency

A quantum theory of the interaction of the atomic Bose condensate with external optical fields has been developed for a two-beam Λ-scheme close to resonance. Regimes have been obtained where the coefficients of Kerr nonlinearity and nonlinear absorption reach giant values and even become negative, which gives rise to the effect of nonlinear electromagnetically induced transparency. The possibility of the efficient generation of quadrature-squeezed light under the condition of the nonlinear compensation of optical losses has been shown.

Lasing and high-temperature phase transitions in atomic systems with dressed-state polaritons

We consider the fundamental problem of high temperature phase transitions in the system of high density two-level atoms off-resonantly interacting with a pump field in the presence of optical collisions (OCs) and placed in the cavity. OCs are considered in the framework of thermalization of atomic dressed state (DS) population. For the case of a strong atom-field coupling condition we analyze the problem of thermodynamically equilibrium superradiant phase transition for the order parameter representing a real amplitude of cavity mode and taking place as a result of atomic DSs thermalization process. Such transition is also connected with condensed (coherent) properties of low branch (LB) DS-polaritons occurring in the cavity. For describing non-equilibrium phase transitions we derive Maxwell-Bloch like equations which account for cavity decay rate, collisional decay rate and spontaneous emission. Various aspects of transitions to laser field formation by using atomic DS levels for both positive and negative detuning of a pump field from atomic transition frequency are studied in detail. It is revealed, that for positive atom-light detuning DS lasing can be obtained in the presence of quasi-equilibrium DS population that corresponds to a true two-level atomic system with the inversion in nonresonant limit.

Quantum operational measurement of amplitude and phase parameters for SU(3) symmetry optical fields

We consider a new approach for describing a quantum optical Bose system with internal Gell-Mann symmetry by means of the SU(3) symmetry polarization map in Hilbert space. The operational measurement of the density (or coherency) matrix elements for the three-mode optical field is discussed for the first time. We have introduced a set of operators that describe the quantum measurement procedure and the behaviour of fluctuations for the amplitude and phase characteristics of the three-level system. A novel twelve-port interferometer for making parallel measurements of the Gell-Mann parameters is proposed. The quantum properties of qutrit W-states in the measurement procedure are examined.

Quantum states of the light for dynamic diffraction in the DFB system

A new method of formation of quantum states of the light in a system with non-linear dynamic diffraction is discussed for the first time. The squeezed states of the light are obtained for two geometries (Bragg and Laue) of non-linear diffraction in a spatially periodic medium. The approach also gives new opportunities for the experimental verification of the quantum properties of the light.