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A. Zh. Muradyan

Publications and source records attributed to A. Zh. Muradyan.

10 recordsLinked to original sources
arXiv2025

Polarimetric Light-Pulse Atom Interferometer: Two-Level Scheme

A new type of atomic interferometer is proposed, in which the traditional method of measuring the state of an atom is replaced by the technique of polarization spectroscopy using the working substance of a clot of condensate of two-level atoms. As a result, the atomic interferometer is freed from needing the above-mentioned multiple repetitions, while maintaining high sensitivity. The Kapitza-Dirac resonance diffraction is used to split the translational motion of the atom. Numerical computations to determine the rotated component of the probing field show that the ratio of the out-put signal to the input signal under normal conditions in a specialized laser physics laboratory using a clot of atomic condensate of alkali metals with a concentration of 10 in 11 power per cm cube and linear dimensions of the order of 1 micrometer as the working substance reaches quite respectable values.

physics.app-ph↗
arXiv2021

Quantum tunneling of a singular potential

Singularity of the potential function makes quantum tunneling problem mathematically underdetermined. To circumvent the difficulties it introduced in physics, a potential singularity cutoff is often used, followed by a reverse limit transition, or is a suitable self-adjoint extension of the Hamiltonian along the entire coordinate axis made. However, both of them somehow affect the singular nature of the problem, and so I discuss here how quantum tunneling will behave if the original singular nature of the Schrodinger equation left untuched. To do this, I use the property of the probability density current that the singularities are mutually destroyed in it. It is found that the mildly singular potential has a finite, but unusual tunneling transparency, in particular, a non-zero value at zero energy of incident particle. The tunneling of one dimensional Coulomb potential exhibits infinitely fast and complete oscillation at the zero energy boundary and a suppresion to zero in the high-energy limit. In the more singular region, the tunneling becomes forbidden, theby repeating the well-known result of the regularized counterparts.

quant-ph↗
arXiv2009

Train of high-power femtosecond pulses: Probe wave in a gas of prepared atoms

We present a new method for generating a regular train of ultrashort optical pulses in a prepared two-level medium. The train develops from incident monochromatic probe radiation travelling in a medium of atoms, which are in a quantum mechanical superposition of dressed internal states. In the frame of used linear theory for the probe radiation, the energy of individual pulses is an exponentially growing function of atom density and of interaction cross section. Pulse repetition rate is determined by the generalized Rabi frequency and can be around 1 THz and greater. We also show that the terms, extra to the dipole approximation, endow the gas by a new property: non-saturating dependence of refractive index on the dressing monochromatic field intensity. Contribution of these nonsaturating terms can be compatible with the main dipole approximation in the wavelength region of about ten micrometers (the range of CO_2 laser) or larger.

quant-ph↗
arXiv2006

Theory of Critical Temperature Adiabatic Change for Ideal Gas Bose-Einstein Condensation in Optical Lattices

We present a scheme of analytical calculations determining the critical temperature and the number of condensed atoms of ideal gas Bose-Einstein condensation in external potentials with 1D, 2D or 3D periodicity. In particular we show that the width of the lowest energy band appears as the main parameter determining the critical temperature of condensation. Is obtained a very simple, proportional to 1/3 degree, regularity for this dependence. The fundamental role of tunneling in physics of condensate establishment is underscored.

cond-mat.other↗
arXiv2003

Decreasing critical temperature of gas BEC in spatially periodic potential and relevance to experiments treated by Mott-Hubbard model

It is shown that the critical temperature of gas Bose-Einstein condensation decreases in deepening periodic potential, in contrast to common regularity in a separate potential well. The physical explanation of this phenomenon is given. Characteristic scale of potential energies decaying the critical temperature is the quantum recoil energy of periodic potential. The theory represents an alternative and direct approach to the experimental results (C.Orzel et al Science 291, 2386 (2001); M.Greiner et al, Nature 415, 39 (2002)) obtained with BEC in optical lattices and treated as the phase squeezing or Mott transition processes.

cond-mat.soft↗
arXiv2002

Anomalous transparency for near-top Bloch states of periodic potential

In the paper are considered stationary (Bloch) states of a particle, in the field of periodic biparabolic type potential. It is shown that while the particle's energy decreases in limits of a single energy band, the probability of the particle to be in barrier-type region of periodic potential increases, in contrary to the expected decreasing. This ''anomalous'' behavior is more pronounced for the near-top bands and monotonically decreases for the higher or lower ones.

quant-ph↗
arXiv2001

Stationary states of Jaynes-Cummings model with atomic center-of-mass quantum motion: direct comparison of standing-wave and counterpropagating-waves cases

The eigenstate problem of the Jaynes-Cummings model on the basis of complete Hamiltonian, including the center-of -mass kinetic energy operator, is treated. The energy spectrum and wave functions in standing-wave (SW)- and counterpropagating waves (CPW)- cases are calculated and compared with each other. It is shown that in CPW-case i) the atomic momentum distribution is asymmetric and somewhat narrower in general; ii) the concept of quasimomentum is not applicable and instead the ordinary momentum concerns the problem; iii) atomic and photonic state distributions are self-consistent, and, in consequence iiii) mean number of photons in the counterpropagating traveling waves and mean atomic momentum match. Explicit analytic expressions for energy eigenvalues and eigenfunctions are found in Tavis -Cummings-type approximation [Phys. Rev. 170, 379(1968)] and is pointed, that it implies only the bounded-like states for atomic center-of-mass motion. It is also shown that if the recoil energy is taken into account, the Doppleron resonance is split into two branches, one of which diverges to Bragg-like resonance in the high-order range.

quant-ph↗
arXiv2000

Optical Transition and Momentum Transfer in Atomic Wave Packets

It is shown that the population Rabi-floppings in a lossless two-level atom, interacting with a monochromatic electromagnetic field, in general are convergent in time. The well-known continuous floppings take place because the restricted choosing of initial conditions, that is when the atom initially is chosen on ground or excited level before the interaction, simultaneously having a definite value of momentum there. The convergence of Rabi-floppings in atomic wave-packet-states is a direct consequence of Doppler effect on optical transition rates (Rabi-frequencies): it gradually leads to ''irregular'' chaotic-type distributions of momentum in ground and excited energy levels, smearing the amplitudes of Rabi-floppings. Conjointly with Rabi-floppings, the coherent accumulation of momentum on each internal energy level monotonically diminishes too.

quant-ph↗
arXiv1999

Large Scale (Multiphoton) Evolution of Atomic Energy Level's Mean Momentum for Single-Photon Absorption/Emission Process

It is shown that a two-level atom, being initially in general superposition state of ground and excited energy levels with mutually different momentum distributions there, gets a large scale evolution in the energy levels momentum distribution. As a consequence the mean momentum of each individual energy level also gets large scale changes, more than the own momentum hbar k of the photon. Because of not completeness of the literature under the hand, we are not sure that this simple phenomenon isn't known in quantum theory of atom-photon interactions or, particularly, in the interferometry of atomic matter waves. One of main purposes of this article is our request to the leading specialists to respond and if the phenomenon is known, send the corresponding references. Thoroughly is discussed the special case, when the atom's preliminary superposition state is created as a result of interaction of the atom with the resonant standing wave. Also it is pointed that in such conditions the mentioned phenomenon can be presented as a transformation of the resonant Kapitza-Dirac splitting of atomic states into the Stern-Gerlach type splitting.

physics.atom-ph↗