Jan Perina Jr. (Olomouc)

Two-beam light with simultaneous anticorrelations in photon-number fluctuations and sub- Poissonian statistics

Twin beams generated in spontaneous parametric down-conversion are endowed with highly nonclassical properties. Their entanglement has been exploited to test the quantum mechanics via the violation of the Bell inequalities, teleport the polarization state of a photon, demonstarate quantum and ghost imaging, develop the methods of ultra-precise quantum measurements and absolute detector calibration, etc. A very efficient method for sub-Poissonian light generation by photon-number-resolved postselection from twin beams has been suggested and experimentally demonstrated to arrive at the states with photon-number fluctuations reduced below the level of the vacuum state. Such states are, in certain sense, complementary to the phase squeezed states well known from, e.g., the detection of gravitational waves. We have developed and utilized the method of photon-number- resolved postselection from twin beams to demonstrate the generation of a new class of quantum states exhibiting anticorrelations in photon-number fluctuations and marginal sub-Poissonian statistics: Two twin beams with a shared signal beam and separated idler beams have been used together with the photon-number-resolving postselection in the signal beam to arrive at two coupled beams with anticorrelations in photon-number fluctuations. Moreover, the beams have exhibited the sub-Poissonian photon-number statistics in their marginal distributions under suitable conditions. The postselected fields with the increasing mean photon numbers have been reconstructed from the experimental photocount histograms by the maximum likelihood approach. Their nonclassical properties have been analyzed by suitable nonclassicality criteria and quantified by the corresponding nonclassicality depths. Determining the appropriate quasi-distributions of integrated intensities with negative values, the performance of different nonclassicality criteria has been judged. Properties of the postselected fields reached both by the used and ideal photon-number-resolved detectors have been mutually compared.