Vol 40, No 4 (2019)

We model the interaction between a qubit and optical radiation field (ORF) using an excited binomial distribution (EBD) and excited negative binomial distribution (ENBD). The explicit form of the density matrix of the qubit–ORF system is given in terms of the photon number distribution. The Mandel parameter is used to quantify the statistical properties of the ORF during the interaction. We derive the relation between the tomographic entropy and the quantum Fisher information of the estimators of model parameters in the EBD and ENBD. We also explore the properties and dynamics of these statistical quantities.

We map the 2+1 Dirac–Moshinsky oscillator (2+1 DMO) into the generalized Jaynes–Cummings model (GJCM), where an external magnetic field is coupled to an external isospin field. We solve analytically the basic equations of the model, where the coherent state is considered as an initial state. The results obtained show that the magnetic field strength and the coupling parameter of the isospin field play important roles when some statistical properties such as the entanglement, population inversion, and degree of coherence are considered. We show that these parameters are important for increasing the entanglement and also demonstrate the collapse and revival phenomena.

We show theoretically and numerically that cold two-level atoms demonstrate unexpectedly complicated motion in an absolutely rigid two-dimensional optical lattice with interfering laser beams. The point-like atoms can move there in a chaotic way resembling motion of particles in a random potential. Chaos arises if the laser frequency is close to the atomic transition frequency where one should take into account the excitation of internal atomic states by the laser field. After loading cold atoms to the lattice, their induced electric dipole moments interact with a spatially inhomogeneous electric field of the two-dimensional standing laser wave. We find the range of the atom–field detuning where the synchronized (with the laser field) component of the atomic dipole moment changes in a random-like manner just after crossing the nodal lines of the standing wave where the electric field is zero. It, in turn, causes irregular changes in the momentum of atoms, leading eventually to chaotic walking of cold atoms in a deterministic potential. We show that adjusting the single control parameter, the atom–field detuning, it is possible to switch between regular and chaotic regimes of motion.

We study the properties of solid-based random lasers by observing spectral emission shape, emission intensity, emission line width, and lasing threshold. Random lasers based on solid polymer film are prepared by combining titania nanoparticles with rhodamine 640 in poly(vinyl alcohol) (PVA) water solution. We compare samples with and without scatterers. Adding nanoparticles to the samples narrows the emission spectrum, and the lasing threshold can be observed. The amount of titanium dioxide (TiO₂) or titania nanoparticles is varied and affects the properties of random lasers. The spectral emission line width becomes narrower, and the lasing threshold decreases when the amount of titania increases. Results obtained show that the properties of solid-based random lasers can be improved by increasing scattering, which enhances the feedback mechanism. The enhanced properties of random lasers are very useful for creating a reliable optical device for future applications in medical and biosensing fields.

Trapped ions nowadays play an important role in both fundamental science and technical applications. Due to its convenient energy structure, singly charged ytterbium ion is widely used in microwave and optical frequency standards, tests of fundamental theories, and quantum information science. In this paper, we present the results of wavelengths measurements in the ²S_1/2→²P_1/2 and ²D_3/2→³[3/2]_1/2 transitions in ¹⁷⁰Yb⁺, ¹⁷¹Yb⁺, ¹⁷²Yb⁺, ¹⁷⁴Yb⁺, and ¹⁷⁶Yb⁺ ions with uncertainties of 50 and 20 MHz, respectively. We reach a factor of three-times improvement in the accuracy with respect to the previously published data, which significantly simplifies the process of initial ion trapping and cooling, in a laser system and an ion trap designed for the YBIS Project aimed for developing a compact and transportable optical clock based on a single ¹⁷¹Yb⁺ ion.

We realize real-time image processing due to nonlinear Fourier-spectrum filtering by an emulsion of submicrometer particles of oil in water. We show that the emulsion of submicrometer particles of oil in water can be used as an effective amplitude–phase filter that nonlinearly changes the amplitude and phase of coherent radiation.