Scientific activity during the last ten years was connected with quantum optics, namely, with the statistical properties of light and, more specifically, with the entangled states generated via spontaneous parametric down-conversion.

The period of 1994-1998 was mainly represented by works on the study of second-order and fourth-order interference effects (interference of fields and intensities, respectively) in various types of light scattering (quasi-elastic scattering by acoustic phonons, Raman scattering by optic phonons, and spontaneous parametric down-conversion).

During the last five years, research activity was connected with the study of entangled two-photon states (also called biphotons) generated via spontaneous parametric down-conversion. A series of papers was focused on the spectral properties of biphotons: the spectral features of two-photon interference observed in the femtosecond pulsed regime, the properties of second-order and fourth-order correlation functions, and the role of group velocity dispersion for biphotons propagating in optical fibres. In other group of works, polarization properties of biphotons were investigated. Biphotons generated in the collinear frequency-degenerate regime were considered as qutrits, i.e., three-state quantum systems. For such qutrits, preparation, measurement, and distinguishing procedures were developed, forming a base for utilizing biphotons in ternary quantum information protocols.

The most recent branch of research activity concerns unitary transformations performed on biphotons, with an application to absolute quantum calibration of photodetectors, and a search for experimental generation of multi-photon states (three-photon states and four-photon states).