A modified Jaynes-Cummings model for an atom interacting with a classical multifrequency field

An open quantum system, which consists of a “dressed” two-level atom, i.e., an atom interacting with a classical multifrequency field, and a single quantized mode of an electromagnetic field, is examined. It is shown that when the frequency of the quantized mode coincides with one of the transition frequencies between the quasienergy levels, two interaction mechanisms, which differ in the dynamics of the populations of the quasienergy states, can be realized. Zh. éksp. Teor. Fiz. 112, 818–827 (September 1997)     

Models of Two-Level Atoms in Quasiperiodic External Fields

We prove that the spectrum of the generalized quasienergy operator of a plane-polarized two-level atom in a strong external quasiperiodic electromagnetic field with nonzero constant Fourier component is pure point, under Diophantine conditions on the frequency ratio, and excluding a small subset of resonant values. The widespread belief that there may be only pure point spectrum in such models is briefly discussed in Section 2 and the circularly polarized case—a well-known soluble model—is revisited from the point of view of the quasienergy operator..     

Dynamic chaos in highly excited states of an anharmonic oscillator in an external electric field

The behavior of an anharmonic quantum oscillator in a harmonic external electric field is examined. The quasienergy is calculated numerically as a function of the field parameters (intensity and frequency) for highly excited states. It depends in complex fashion on frequency and field intensity near resonance. Quasi-intersection of levels is observed in a broad range of quantum numbers. These effects are manifestations of dynamic chaos in highly excited states of an anharmonic oscillator in an external field. Omsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 11–18, February, 1998.     

Method of resonance near-field optical microscopy

We have solved the problem in which a thin metal wafer (probe) with a nanohole interacts with the flat surface of a metastructured film consisting of metal nanoparticles in an external optical radiation field. Nanoparticles are considered as two-level atomic systems. This interaction of the wafer-probe and the flat surface in the external optical radiation field gives rise to optical near-field resonance, the frequency of which differs significantly from the natural frequencies of two-level atoms in the medium and the probe. The fields inside and outside the probe and metastructured film are calculated in the near-field and far-field zones. The maximum resolution, which is achievable in the suggested scheme of near-field optical microscopy, can reach about 10 nm. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 499–506, July–August, 2007.     

The quantum theory of an ideal superlattice responding to far-infrared laser radiation

Minibands of quasienergies can be defined for a superlattice interacting with far-infrared laser radiation. It is demonstrated that the width of these quasienergy minibands depends not only on the parameters of the superlattice, but also on strength and frequency of the driving laser field. In particular, the width approaches zero at certain values of these parameters. A strong coupling ansatz, combined with perturbation theory for degenerate quasienergy states, leads to a detailed understanding of these results.     

Two-level electron dynamics in a strong variable external field

This paper studies the quantum dynamics of an electron in a double-well potential subject to a strong time-periodic nonharmonic external field. The quasienergy spectrum of the system is calculated and an expression for the electron density distribution is derived. It is found that under certain conditions imposed on the shape of the excitation, the electron wave packet gets locked, into one potential well, as it were, and is unable to tunnel through the potential barrier. Zh. éksp. Teor. Fiz. 112, 1209–1225 (October 1997)     

Boundary-value problems in near-field optical microscopy and optical size resonances

We have solved a boundary-value problem for a ball probe interacting with a flat dielectric surface in an external optical radiation field. This interaction gives rise to the optical size resonance at frequencies significantly different from the natural frequencies of two-level atoms both in the medium and in the probe with allowance for the local field corrections. These resonances depend significantly on the distance from the probe center to the surface, on the ball probe size, on the concentration of two-level atoms in the probe and in the medium, on the spectral line width, and on the atomic inversion. The field strengths inside and outside the ball probe and a semiinfinite dielectric medium have been calculated in the near-field and wave zones. It is shown that the proposed electrodynamic theory of optical near-field microscopy agrees with the results of experimental measurements.     

Overcoming Decoherent Effects from Squeezed Vacuum Reservoir

A strategy is investigated to overcome the decoherence for open quantum system by controlling external parameters. The results show that output state may be a pure state in some critical magnetic field parameters which depend on the decay rates so that one may perfectly preserve memory of initial single-qubit states at the finial state under some conditions. The way is applied to two-level atomic systems interacting with squeezed vacuum reservoir.     

Charging Quantum Batteries with a General Harmonic Driving Field

A general harmonic driving field was considered for improving the charging efficiency of the quantum battery system. Charge saturation was used to describe the charging efficiency, where the charging mode is divided into saturated and unsaturated. The relationships between the time-dependent charge saturation and parameters of the general driving field were evaluated both analytically and numerically. The Floquet theorem was used to express time-dependent charge saturation with the quasienergy and Floquet states of the system. The analytical and numerical results were used to identify the best parameter values for optimizing the charging efficiency.     

Quantum electrodynamic perturbation theory based on electrodynamics with an external field

A method is proposed for construction of mean values of quantum quantities in quantum optics and electrodynamics on the basis of exact solutions of the corresponding problems of electrodynamics with an external field. To illustrate the method the mean energy of a two-level atom in the Raby problem is calculated. It is shown that the mean value obtained with a specified accuracy coincides with the result of exact quantum electrodynamic calculation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 7–10, September, 1983.     

Controlling multiparticle correlations with a strong laser field

The collective interaction via a surrounding thermalized electromagnetic reservoir of a two-level multiatom sample with an external applied strong coherent field is investigated. In a small sample following Dicke’s model, even at the exact resonances, very strong pumping leads to a complete transfer of the population into a particular dressed-state. This way very large Rabi frequencies are shown to modify and control the interatomic correlations in a system of spatially separated atoms of few wavelengths extend.     

Realization of population inversion in a two-level system by damping field

We propose a new method for reversing the quantum state of a two-level system. From solving the time-dependent Schrödinger equation numerically, we show that by applying a classical decaying oscillatory field the state in a two-level system can be completely reversed if the parameters of the field satisfy certain conditions. The transition probability from one level to the other is calculated for different parameters and its maximum value can reach unity. By using such field with specific oscillatory frequency the Rabi oscillations between two levels in the case of applying a constant field can be suppressed and a stable manipulation of the quantum state can be performed. The estimation of such manipulation by using laser pulse acting on the states of hydrogen atom shows that the population inversion higher than 0.9 may be realized in less than 2 fs.     

Quantum nonlinear resonance in a strong electromagnetic field

The motion of a one-dimensional quantum weakly anharmonic system under the influence of harmonic external field is treated in the range where the transition frequency between the neighboring levels is close to the frequency of the harmonic field (quantum nonlinear resonance). The case of the strong external field, in which the Rabi frequency for the transitions is large in comparison with the field frequency, is studied. The expression for compact wavepackets of quasienergy states that change their content and width periodically (and, possibly, strongly), is obtained.     

Frequencies of two running circular electromagnetic waves in a rotating frame of reference

The frequencies of two running electromagnetic waves interacting with a system of identical two-level atoms in a rotating frame of reference have been calculated with the help of quantum electrodynamics and the covariant formalism.The existence of two states of the perturbed electromagnetic field with degenerate and nondegenerate frequencies has been shown.     

Dynamical evolution of a two-level atom in a monomode chaotic field

The dynamical evolution of a two-level atom interacting with a monochromatic chaotic field is expressed in terms of a series of functions of the field photon number n. The series are evaluated in the approximation of large 〈n〉, by using the Stirling numbers of the second kind and their properties. The calculated mean values of atomic parameters show a time behaviour that is quite different from an exponential decay to the steady state. In particular they reach values below the steady state values and then evolve towards the stationary conditions with positive derivative. An evaluation of the decay time in the present scheme is also given for excited atomic states.     

消除简并双光子过程中二能级原子的消相干性

研究了置于外部环境(热库)中的二能级原子在外加驱动场时原子的消相干问题.得到简并双光子过程中原子约化密度算符非对角元.在二能级原子的消相干被消除的情况下,讨论外加驱动场的特性. 关键词： 简并双光子过程 二能级原子 消相干性     

Instability of the tunneling destruction effect in a quasi-periodically driven two-level system

Here we consider the dynamics of a two-level system under an external time-dependent field. We show that in the case of a bichromatic field the dynamical localization effect is strongly sensitive with respect to the commensurability of the driving frequencies. Received 8 May 2002 / Received in final form 4 July 2002 Published online 24 September 2002 RID="a" ID="a"e-mail: Sacchetti@unimo.it     

A new parallel algorithm for simulation of spin glasses on scales of space-time periods of external fields with consideration of relaxation effects

We have investigated the statistical properties of an ensemble of disordered 1D spatial spin chains (SSCs) of finite length, placed in an external field, with consideration of relaxation effects. The short-range interaction complex-classical Hamiltonian was first used for solving this problem. A system of recurrent equations is obtained on the nodes of the spin-chain lattice. An efficient mathematical algorithm is developed on the basis of these equations with consideration of advanced Sylvester conditions which allows one to step by step construct a huge number of stable spin chains in parallel. The distribution functions of different parameters of spin glass system are constructed from first principles by analyzing the calculation results of the 1D SSCs ensemble. It is shown that the behaviors of different distributions parameters are quite different even at weak external fields. The ensemble energy and constants of spin-spin interactions are being changed smoothly depending on the external field in the limit of statistical equilibrium, while some of them such as the mean value of polarizations of the ensemble and parameters of its orderings are frustrated. We have also studied some critical properties of the ensemble such as catastrophes in the Clausius-Mossotti equation depending on the value of the external field. We have shown that the generalized complex-classical approach excludes these catastrophes, which allows one to organize continuous parallel computing on the whole region of values of the external field including critical points. A new representation of the partition function is suggested based on these investigations. Being opposite to the usual definition, it is a complex function and its derivatives are everywhere defined, including at critical points.