Featured Researches

Atomic Molecular And Optical Physics

Quantum state diffusion with a moving basis: computing quantum-optical spectra

Quantum state diffusion (QSD) as a tool to solve quantum-optical master equations by stochastic simulation can be made several orders of magnitude more efficient if states in Hilbert space are represented in a moving basis of excited coherent states. The large savings in computer memory and time are due to the localization property of the QSD equation. We show how the method can be used to compute spectra and give an application to second harmonic generation.

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Atomic Molecular And Optical Physics

Quantum uncertainties in coupled harmonic oscillator

In this paper we analyze the quantum uncertainties and the photon statistics in the interaction between the two modes of radiation by treating them as coupled harmonic oscillator with the motivation of controlling quantum properties of one light beam by another. Under the rotating wave approximation (RWA) we show that if initially one of the modes is coherent and the other one squeezed, then the squeezing and non-Poissonianness of the photon statistics can transfer from one mode to the other. We give a parametric study of these properties depending upon interaction time and the degree of initial squeezing in one of the modes.

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Atomic Molecular And Optical Physics

Right-unitary transformation theory and applications

We develop a new transformation theory in quantum physics, where the transformation operators, defined in the infinite dimensional Hilbert space, have right-unitary inverses only. Through several theorems, we discuss the properties of state space of such operators. As one application of the right-unitary transformation (RUT), we show that using the RUT method, we can solve exactly various interactions of many-level atoms with quantized radiation fields, where the energy of atoms can be two levels, three levels in Lambda, V and equiv configurations, and up to higher (>3) levels. These interactions have wide applications in atomic physics, quantum optics and quantum electronics. In this paper, we focus on two typical systems: one is a two-level generalized Jaynes-Cummings model, where the cavity field varies with the external source; the other one is the interaction of three-level atom with quantized radiation fields, where the atoms have Lambda-configuration energy levels, and the radiation fields are one-mode or two-mode cavities.

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Atomic Molecular And Optical Physics

Single-Mode Cavity-QED of a Raman Interaction

We consider a single Rydberg atom having two degenerate levels interacting with the radiation field in a single-mode ideal cavity. The transition between the levels is carried out by a Λ -type degenerate two-photon process via a third level far away from single-photon resonance. At the start of interaction, the atom is considered to be in a coherent superposition of its two levels and the field in a coherent state. We study the dynamics of the atomic as well as the field states. The squeezing in the quadratures of atomic states can reach up to 100% . The cavity field evolves to a statistical mixture of two coherent fields with the phase difference between them decided by the interaction time. Analysis of entropies of the atom and the field shows that the two systems are dis-entangled periodically in certain cases.

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Atomic Molecular And Optical Physics

Some remarks on the two-electron atom

New, approximate, two-electron wavefunctions are introduced for the two-electron atoms (cations), which account remarkably well for the ground-state energies and the lowest-excxited states (where available). A new scheme of electronic configurations is also proposed for the multi-electron atoms.

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Atomic Molecular And Optical Physics

Spin-rotation coupling in ferromagnetic clusters

We examine the magnetic response of free clusters considering the spin direction and the cluster orientation as the only active degrees of freedom. The average magnetization in small fields approaches the Langevin value for paramagnets, depending on the degree to which the Hamiltonian preserves symmetries. Superparamagnetic behavior is not achievable within models considering only these degrees of freedom.

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Atomic Molecular And Optical Physics

Squeezing in the interaction of radiation with two-level atoms

We propose a simple experimental procedure to produce squeezing and other non-classical properties like photon antibunching of radiation, and amplification without population inversion. The method also decreases the uncertainties of the angular-momentum quadratures representing the two-level atomic system in the interaction of the two-level atoms with quantized radiation.

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Atomic Molecular And Optical Physics

State Measurements with Short Laser Pulses and Lower-Efficiency Photon Detectors

It has been proposed by Cook (Phys. Scr. T 21, 49 (1988)) to use a short probe laser pulse for state measurements of two-level systems. In previous work we have investigated to what extent this proposal fulfills the projection postulate if ideal photon detectors are considered. For detectors with overall efficiency less than 1 complications arise for single systems, and for this case we present a simple criterion for a laser pulse to act as a state measurement and to cause an almost complete state reduction.

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Atomic Molecular And Optical Physics

Stimulated Enhancement of Cross-Section by a Bose-Einstein Condensate

This paper examines the feasibility of constructing an experiment which detects the atomic stimulation of a photon emission process. A beam of atoms (bosons) in an excited state is passed over an atomic trap which traps the atoms when they are in their internal ground state. When the trap contains a Bose-Einstein condensate, the cross-section for absorption of the atomic beam is increased. We examine a particular model in which this atom-stimulation is observable, and is also characterised by the emission of photons in a narrow cone in the direction of the atomic beam.

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Atomic Molecular And Optical Physics

Stimulation of Beta Decay due to a Bose-Einstein Condensate

Nuclear processes can be stimulated by the presence of a macroscopic number of bosons in one of the final states. We describe the conditions necessary to observe the atom-stimulation of a beta decay process. The stimulation may be observable if it becomes possible to produce a Bose-Einstein condensate with the order of 10 14 atoms in a trap.

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