Coherent Trapping States Research Articles

Uncondensed atoms in the regime of velocity-selective coherent population trapping

We consider the model of a Bose condensate in the regime of velocity-selective coherent population trapping. As a result of interaction between particles, some fraction of atoms is outside the condensate, remaining in the coherent trapping state. These atoms are involved in brief events of intense interaction with external resonant electromagnetic fields. Intense induced and spontaneous transitions are accompanied by the exchange of momenta between atoms and radiation, which is manifested as migration of atoms in the velocity space. The rate of such migration is calculated. A nonlinear kinetic equation for the many-particle statistical operator for uncondensed atoms is derived under the assumption that correlations of atoms with different momenta are insignificant. The structure of its steady-state solution leads to certain conclusions about the above-mentioned migration pattern taking the Bose statistics into consideration. With allowance for statistical effects, we derive nonlinear integral equations for frequencies controlling the migration. The results of numerical solution of these equations are represented in the weak interatomic interaction approximation.

Dynamic and steady control of quantum coherence in photonic crystals via the Zeeman effect

The dynamic evolution of a multi-level atom in the three-dimensional photonic crystal under an applied magnetic field is investigated. By combining the Zeeman effect with the photonic band gap effect, the dynamic quantum superposition states and steady quantum coherent trapping states of the atom can be flexibly controlled. This paves the way for coherent manipulation of quantum states in the solid-state system, which has important applications in quantum information processing.

Coherent trapping of a three-level atom in a circularly polarized light

Using semiclassical theory, we study coherent trapping of a three-level atom, where the atom possesses a momentum of its center-of-mass motion and is irradiated only by a classical circularly polarized electromagnetic wave. We find that if the atom is initially in a coherent trapping state of it, under the zero- or first-order approximation, the atom is absolutely or nearly in the state hereafter.

INFLUENCE OF CAVITY LOSS ON GENERATION OF STEADY STATE FOURTH-ORDER AND SQUARED AMPLITUDE SQUEEZING IN MICROMASER

The generation of the steady state fourth-order squeezing and squared amplitude squeezing in a micromaser by the coherent trapping approach is investigated. The results show that if two-level atoms injected into the cavity are initially in coherent state and the flight time of the atoms inside the cavity satisfies the trapping condition, the field can evolve into a coherent trapping state which exhibits steady state fourth-order squeezing and squared amplitude squeezing in the cavity as long as the flux of the atoms is moderately large.

Coherent phenomena in multilevel systems with closed interaction contour

The work presented considers a new coherent phenomenon, i.e. the influence of the phases of electromagnetic fields interacting with a multilevel system on the character of excitation of this system. On the basis of analysing the equation for an N-level quantum system density matrix, it was established that in multilevel systems containing a closed contour of transitions, resonantly interacting with the field, stationary populations always depend on the total interaction contour phase Phi . For the simplest multilevel systems, i.e. three-level, the authors have obtained analytical expressions, connecting populations with the relative field phase in such systems. Thus, for a Lambda system, interacting with three resonant electromagnetic fields, it is discovered that, depending on the total phase value of the transition contour, both destruction and successive restoration of a coherent trapping state can take place. The work provides qualitative explanations of phase effects and suggests some possibilities for their application.

Coherent trapping of populations in a three-level two-mode model with multiphoton transitions

A two-mode three-level model of an atom with multiphoton transitions is studied taking into account detuning by the formalism of dressed states. Transition probabilities are calculated and quantum mechanical analogs of the Rabi frequencies are found. A possibility for the existence of coherent trapping of populations is shown in such a model and the coherent trapping states are found.