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Vitalie Eremeev

Publications and source records attributed to Vitalie Eremeev.

23 records · Page 2Linked to original sources

Thermally generated long-lived quantum correlations for two atoms trapped in fiber-coupled cavities

A theoretical model for driving a two qubit system to a stable long-lived entanglement is discussed. The entire system is represented by two atoms, initially in ground states and disentangled, each one coupled to a separate cavity with the cavities connected by a fiber. The cavities and fiber exchange energy with their individual thermal environments. Under these conditions, we apply the theory of microscopic master equation developed for the dynamics of the open quantum system. Deriving the density operator of the two-qubit system we found that stable long-lived quantum correlations are generated in the presence of thermal excitation of the environments. To the best of our knowledge, there is no a similar effect observed in a quantum open system described by a generalized microscopic master equation in the approximation of the cavity quantum electrodynamics (CQED).

quant-ph↗

Towards a random laser with cold atoms

Atoms can scatter light and they can also amplify it by stimulated emission. From this simple starting point, we examine the possibility of realizing a random laser in a cloud of laser-cooled atoms. The answer is not obvious as both processes (elastic scattering and stimulated emission) seem to exclude one another: pumping atoms to make them behave as amplifier reduces drastically their scattering cross-section. However, we show that even the simplest atom model allows the efficient combination of gain and scattering. Moreover, supplementary degrees of freedom that atoms offer allow the use of several gain mechanisms, depending on the pumping scheme. We thus first study these different gain mechanisms and show experimentally that they can induce (standard) lasing. We then present how the constraint of combining scattering and gain can be quantified, which leads to an evaluation of the random laser threshold. The results are promising and we draw some prospects for a practical realization of a random laser with cold atoms.

physics.atom-ph↗

Specificity of Phase Transition of Quasi-Spin System in Two-Quantum Exchange with Thermostat

The quantum phase transition of the system of N radiators in case of two-photon exchange interaction with cavity electromagnetic field is considered. It is shown that for this system the atom-field exchange integral increases with the increase of temperature. This effect generates peculiarities in phase transition picture. The process of nonlinear exchange between the quasi-spins leads to the increase of critical temperature as compared to traditional second order phase transition of quasi-spin system.

quant-ph↗

Cooperative Two-Quantum Interaction of Excited System with Bath

The problem of the two-photon coherent generation of entanglement photon pairs in Quantum Optics has been intensively studied for the last years. It is important to note that the two-quantum cooperative effects play a main role in other fields of physics as well. The collective processes in Condensed Matter have many analogical proprieties with cooperative radiation effects in Quantum Optics. Recently the two-quantum generation of entanglement photons and its applications in information technology and communication has been intensively studied. The new cooperative emission phenomenon for dipole-forbidden transitions of inverted system of radiators can be observed in the processes of the two-photon spontaneous emission.

cond-mat.stat-mech↗

The size impact on evolutionary dynamics of agents-cluster

A cluster theory based mathematical model was developed and used to simulate the dynamics of a system composed of a large number of interacting agents-clusters with different size. The case of a system formed by a constant total number of economic units (agents) in metastable (partial) equilibrium was considered, and the size effect on the formation of the groups (clusters) of agents was particularly elucidated. We prove that the fragmentation and coagulation rates of groups of agents definitely depend on the size of the group.

physics.soc-ph↗