The laboratory of Quantum Information and Quantum Optics (QIQO) was organized in the summer of 2006 on the basis of Spontaneous Parametric Down-Conversion laboratory. It was designated to work on specific topics in the new field of quantum information and quantum communication. Research themes of QIQO laboratory cover the following topics:

• Two-photon fields interferometry

  Possible applications - development of quantitative methods to analyze the degree of entanglement of two-photon states, as well as engineering of specific states for quantum information and communication purposes.

  This direction is the main one and serves as a basis for all other activities. We investigate various interferometric schemes capable of revealing the non-classical features of biphoton field generated in the process of spontaneous parametric down-conversion (SPDC). Depending on the phase or group delay values, second or fourth moments of the field are amplified or suppressed. In the first case the intensity of two-photon field is analyzed with a single detector, while in the second case the coincidence counts of two detectors working in the photon-counting mode are of interest.

• Engineering and statistical reconstruction of high dimensional optical states (D>2)

  Possible applications - development of dense coding systems and quantum cryptography systems.

  We are interested in generating quantum states of light described by three-, four-, and multi-level systems. Such states are called qutrits, ququarts and qudits. It turns out, that biphoton field is a convenient object for experimental realization of such states. Methods underlying the state engineering in this case are transformations of polarization, spatial and frequency modes of biphoton light. Statistical methods of data analysis are applied for quantum state reconstruction.

• New methods of entangled states generation and their applications in spectroscopy

  Possible applications - spectroscopy of spatially-inhomogeneous ferroelectrics.

  A simple idea underlies experiments in this field - if an optical state is generated in the material with a priori unknown properties, one can obtain information about the material properties by measuring the state at the output. The specific point here is that the generated states are highly non-classical, so it is not so easy to compare the results with known methods of spectroscopy (although it is partly possible). Ferroelectric crystals with quasi-regular spatial domain structure are studied. Such materials are both sources of photon pairs and effective polarization transformers.

• Development of photon counting techniques in 1.5 micrometer wavelength range

  Possible applications - quantum key distribution systems.