Relaxation and storage of multiparticle entangled states of atoms in a collective thermostat

Multiparticle entangled states that are the generalization of the W class states and can be reduced to Dicke states are considered. The master equation describing the collective decay of atoms in a cavity is derived for the Tavis-Cummings model in the dispersive limit. The entangled states of atoms that are retained in the process of collective decay are found. The scheme for recording and storage of these states in a collective thermostat is presented.     

Fractional quantum Hall states of atoms in optical lattices

We describe a method to create fractional quantum Hall states of atoms confined in optical lattices. We show that the dynamics of the atoms in the lattice is analogous to the motion of a charged particle in a magnetic field if an oscillating quadrupole potential is applied together with a periodic modulation of the tunneling between lattice sites. In a suitable parameter regime the ground state in the lattice is of the fractional quantum Hall type, and we show how these states can be reached by melting a Mott-insulator state in a superlattice potential. Finally, we discuss techniques to observe these strongly correlated states.     

On relaxation of entangled states in a collective thermostat

A kinetic equation describing collective relaxation process in the dispersion limit is derived for an ensemble of two-level atoms placed in a cavity and interacting with one cavity mode. Multiatom entangled states belonging to the set of Dicke states and insensitive to collective decay are found. A scheme for recording, storing, and reading these states with participation of spatially multimode light is reported.     

Stable states of a relativistic harmonic oscillator imbedded in a random stochastic thermostat

An analysis in phase space of the behavior of a relativistic four-dimensional harmonic oscillator undergoing stochastic interactions shows that the group of linear canonical transformations in phase space which leaves invariant the Poisson brackets is anSp(12,4) group, withSp(12,4)U(6,2)SU(1,1)SO(6,2). The application of Cartan's treatment to its behavior implies a classification of its stable states characterized by a set of discrete numbers.     

Efficient scheme for entangled states and quantum information transfer with trapped atoms in a resonator

A protocol is proposed to generate atomic entangled states and implement quantum information transfer in a cavity quantum electrodynamics system. It utilizes Raman transitions or stimulated Raman adiabatic passages between two systems to entangle the ground states of two three-state Λ-type atoms trapped in a single mode cavity. It does not need the measurements on cavity field nor atomic detection and can be implemented in a deterministic fashion. Since the present protocol is insensitive to both cavity decay and atomic spontaneous emission, it may have some interesting applications in quantum information processing.     

The bound states problem in quantum electrodynamics and vacuum polarization effects in muonic atoms

Quantum electrodynamic bound states in strong electromagnetic fields are considered. It is shown that the dynamics of the system can not be described completely in the adiabatic S-matrix approach. Vacuum polarization effects in muonic atoms are studied using the paradigm of generalized quantum dynamics. This approach leads to additional correction terms.     

Transition between quantum states in a parallel-coupled double quantum dot

Strong electron and spin correlations in a double quantum dot (DQD) can give rise to different quantum states. We observe a continuous transition from a Kondo state exhibiting a single-peak Kondo resonance to another exhibiting a double peak by increasing the interdot coupling (t) in a parallel-coupled DQD. The transition into the double-peak state provides evidence for spin entanglement between the excess electrons on each dot. Toward the transition, the peak splitting merges and becomes substantially smaller than t because of strong Coulomb effects. Our device tunability bodes well for future quantum computation applications.     

Stationary states in a quantum gravity model

A model theory for quantized gravity is discussed where only selected degrees of freedom are quantized. The concept of stationary states is introduced. It is shown that the Planck length arises as a lower bound to the space-time length scale in a natural way.     

Laser-induced quantum adsorption of atoms on a surface

A method of the quantum adsorption of atoms on a surface is proposed and experimentally implemented. The loading of atoms into a surface potential well (adsorption) occurs due to the loss of kinetic energy in the process of the inelastic collision of two laser-excited atoms. This scheme is implemented for Rb atoms adsorbed on the surface of a YAG crystal. The possibility of producing microstructures of arbitrary shape that consist of atoms localized on the dielectric surface is also demonstrated.     

Strain-induced quantum ring hole states in a gated vertical quantum dot

We have experimentally investigated the hole states in a gated vertical strained Si/SiGe quantum dot. We demonstrate the inhomogeneous-strain relaxation on the lateral surface creates a ringlike potential near the perimeter of the dot, which can confine hole states exhibiting quantum ring characteristics. The magnetotunneling spectroscopy exhibits the predicted periodicity of energy states in phi/phi(0), but the magnitude of the energy shifts is larger than predicted by simple ring theory. Our results suggest a new way to fabricate and study quantum ring structures.     

好腔中的Bell态原子与纠缠相干态光场相互作用系统的保真度

考虑原子间偶极相互作用,求出好腔中的Bell态原子与纠缠相干态光场相互作用系统的保真度.结果表明,对于理想腔,若原子初始时刻处于相干保持态,系统保真度始终等于1;若原子初始时刻处于其余Bell态之一.腔场初态的平均光子数很小,系统保真度在0～1之间作周期性振荡,随着腔场初态的平均光子数的增加,系统保真度的振荡频率增大,振幅减小.对于好腔,若原子初始时刻处于相干保持态,系统保真度呈指数单调衰减;若原子初始时刻处于其余Bell态之一,系统保真度呈指数振荡衰减,且随着腔场初态的平均光子数的增加,系统保真度的振荡频率增大,振幅减小.     

好腔中的Bell态原子与纠缠相干态光场相互作用系统的保真度

考虑原子间偶极相互作用,求出好腔中的Bell态原子与纠缠相干态光场相互作用系统的保真度。结果表明,对于理想腔,若原子初始时刻处于相干保持态,系统保真度始终等于1;若原子初始时刻处于其余Bell态之一,腔场初态的平均光子数很小,系统保真度在0～1之间作周期性振荡,随着腔场初态的平均光子数的增加,系统保真度的振荡频率增大,振幅减小。对于好腔,若原子初始时刻处于相干保持态,系统保真度呈指数单调衰减;若原子初始时刻处于其余Bell态之一,系统保真度呈指数振荡衰减,且随着腔场初态的平均光子数的增加,系统保真度的振荡频率增大,振幅减小。     

Gravity-sensitive quantum dynamics in cold atoms

We subject a falling cloud of cold cesium atoms to periodic kicks from a sinusoidal potential created by a vertical standing wave of laser light. By controllably accelerating the potential, we show quantum accelerator mode dynamics to be highly sensitive to the effective gravitational acceleration when close to specific, resonant values. This quantum sensitivity to a control parameter is reminiscent of that associated with classical chaos and promises techniques for precision measurement.     

Lifetime of core two-hole states in atoms

The lifetime of core two-hole states in atoms is discussed using an atomic many-body theory. The lifetime widths of the two-hole states with the core holes in the Lx (X = l–3) shells of Ar atom are calculated by an ab initio atomic many-body theory (Green's function method using the extended random-phase approximation with exchange (RPAE)). The present theory gives good agreement with experiment. The changes not only in the Coster-Kronig electron kinetic energy but also in the polarization effect on the Coster-Kronig electron by the presence of extra two holes created by decay of the partner hole or by the presence of the partner hole, affects considerably the lifetime width of the two-hole state in Ar atom so that it deviates much from the sum of that of the individual hole.     

Principle of forming bound states of atoms in a laser field

It has been shown that different regimes of forming bound states of colliding atoms are possible due to their near-field interaction in a laser field. Analysis is performed for room temperature and a weak laser field under the conditions of smooth scanning of the laser radiation frequency in dependence on frequencies of near-field optical resonances.