Precision protection through cosmic string in quantum metrology

The dynamics of the quantum Fisher information of the parameters of the initial atomic state and atomic transition frequency is studied, in the framework of open quantum systems, for a static polarizable two-level atom coupled in the multipolar scheme to a bath of fluctuating vacuum electromagnetic fields in cosmic string space-time. Our results show that with the presence of cosmic string, the quantum Fisher information becomes position and atomic polarization dependent. It may be enhanced or depressed as compared to that in flat space-time case. Remarkably, when the atom is extremely close to the cosmic string and the polarization direction of the atom is perpendicular to the direction of the cosmic string, the quantum Fisher information has been totally protected from the fluctuating vacuum electromagnetic fields. So on the one hand, near a cosmic string, precision of estimation can be enhanced by ranging the radial distance between the probe atom and the cosmic string; on the other hand, the cosmic string can be sensed by studying the distribution of parameter induced state-separation.

Coherent energy transfer of a pair of two-level atoms

The coherent energy transfer efficiency of a pair of two-level atoms is studied theoretically and its mathematical expression has been deduced. The problem of atoms coherent energy transfer theory is treated by quantum perturbation theory and equivalent method replacing atomic dipole field with light field of the same frequency. The detuning between the donor atom transition frequency and the acceptor atom transition frequency has been studied in the theory. With the increase of the detuning of the two-atomic transition frequency, the energy transfer efficiency decays rapidly. In the case of two-atomic transition frequency resonance, the coherent resonance energy transfer efficiency is directly proportional to the square of the sine of the minus three power of the distance between two atoms and the energy transfer efficiency is periodically decaying over time. The coherent resonance energy transfer efficiency is inversely proportional to the six power of the distance between the two atoms in the first-order approximation.

Spatial Distribution of Atoms in the Field of Intersecting Standing Bichromatic Light Waves

We have shown that, by properly detuning the carrier frequencies in each of two perpendicularly intersecting bichromatic waves from the atomic transition frequency, it is possible to create a two-dimensional trap for atoms, if the wave intensities are sufficiently high. At the zero and near-zero values of the initial wave phases, as well as at the phase shift between the intersecting waves equal to п or close to п values, the dynamic spatial patterns of atoms consisting of square cells with the side length equal to л/√2 are formed. Numerical simulations were carried out for sodium atoms.

Spontaneous decay in cold dense atomic systems: caloric effect and spectrum of emitted light

We discuss collision-induced spontaneous decay in a system of cold atoms and caloric effect manifesting in the heating of the atomic system during spontaneous decay. It is shown that the caloric effect is caused by inelastic atom–atom collisions accompanied by the spontaneous emission of photons. Because of the imbalance between the rate of emission of the photons with the frequency higher and lower than the atomic transition frequency, the atomic system, under some conditions, is heated up. The value of the critical temperature is found, which separates the regions where the collision-induced spontaneous decay is exothermic and endothermic.