ИСТИНА

The main objective of the work relates to investigation of mode structure of the correlated non-classical (biphoton) and classical (thermal) light beams. At the first stage we are focussing on multimode entanglement of bipartite systems. Several operational quantifiers that can be measured in experiment (Fedorov’s ratio, Schmidt number and subsystem purity) will be discussed. Based on spontaneous parametric down conversion we consider multidimensional optical bipartite system with controllable dimension and entanglement degree. A concept of Schmidt decomposition plays a central role and we discuss some ways how to perform the measurements in Schmidt basis. In particular we analyze experimental challenges with measurement correlation properties of biphoton states with angular and frequency degrees of freedom. Then we apply the developed technique for selecting Schmidt modes [1] to quasi-thermal light. Usual Hanbury Brown and Twiss scheme is used for revealing intensity correlations of the quasi-thermal source (rotating ground disk). After proper preparation of the thermal light beam by means of appropriate lenses and apertures we introduce the spatial light modulator (SLM) followed by single-mode fiber in one arm of intensity interferometer followed by single-mode fiber. The other channel of the interferometer is supplied with single-mode fiber which might be scanned in the transverse direction(s). Switching by SLM between different Hermite-Gauss modes we check the angular correlation function in the fourth order in the field. The results show that there is no correlations ( ) between orthogonal Hermite-Gauss modes while choosing the same modes the corresponding meaning reaches its maximal value