19 research outputs found
Testing Ultrafast Two-Photon SpectralAmplitudes via Optical Fibres
No full textWe test two-dimensional TPSA of biphoton light emitted
via ultrafast spontaneous parametric down-conversion (SPDC) using the
effect of group-velocity dispersion in optical fibres. Further, we apply this
technique to demonstrate the engineering of biphoton spectral properties by
acting on the pump pulse shape
Experimental characterization of multi-photon entanglement with intensity correlation functions
No full text
Generation of bright squeezed vacuum in the Karassiov states
No full textWe suggest an experimental procedure allowing one to prepare squeezed vacuum in a special type of generalized Bell states, first introduced by V.P. Karassiov. We present the first results on the experimental generation of such states and observation of their polarization properties
Macroscopic Pure State of Light Free of Polarization Noise
No full textThe preparation of completely nonpolarized light is seemingly easy; an everyday example is sunlight. The task is much more difficult if light has to be in a pure quantum state, as required by most quantum-technology applications. The pure quantum states of light obtained so far are either polarized or, in rare cases, manifest hidden polarization; even if their intensities are invariant to polarization transformations, higher-order moments are not. We experimentally demonstrate the preparation of the macroscopic singlet Bell state, which is pure, is completely nonpolarized, and has no polarization noise. Simultaneous fluctuation suppression in three Stokes observables below the shot-noise limit is demonstrated, opening perspectives for noiseless polarization measurements. The state is shown to be invariant to polarization transformations. This robust highly entangled isotropic state promises to fuel important applications in photonic quantum technologies
Possibility Investigation of Experimental Verification of General Bell Inequality Violation for Polarization Scalar Light Based Realization
No full textWe discuss the fundamental problems of nonclassical correlations and microscopic entanglement experimental observation possibility for multiphoton quantum light beams. Optical beams of multiphoton nonclassical light are of practical interest due to possibility of applications in quantum metrology and quantum informatics. Quantum macroscopic states of light are the significant information carrier in practical realization of quantum computing algorithms, quantum dense coding, quantum key distribution, quantum teleportation and other cases of quantum communications. And quantum macroscopic light beam can be used as high sensitive probe field in special type spectroscopy and in light sources and detectors etalonless calibration
Interference of macroscopic beams on a beam splitter: phase uncertainty converted into photon-number uncertainty
No full textSqueezed-vacuum twin beams, commonly generated through parametric downconversion, are known to have perfect photon-number correlations. According to the Heisenberg principle, this is accompanied by a huge uncertainty in their relative phase. By overlapping bright twin beams on a beam splitter, we convert phase fluctuations into photon-number fluctuations and observe this uncertainty as a typical 'U-shape' of the output photon-number distribution. This effect, although reported for atomic ensembles and giving hope for phase super-resolution, has never been observed for light beams. The shape of the normalized photon-number difference distribution is similar to the one that would be observed for high-order Fock states. It can be also mimicked by classical beams with artificially mixed phase, but without any perspective for phase super-resolution. The probability distribution at the beam splitter output can be used for filtering macroscopic superpositions at the input
COMPARATIVE TEST OF TWO METHODS OF QUANTUM EFFICIENCY ABSOLUTE MEASUREMENT BASED ON SQUEEZED VACUUM DIRECT DETECTION
No full text We realize and test in experiment a method recently proposed for measuring absolute quantum efficiency of analog photodetectors. Similar to the traditional (Klyshko) method of absolute calibration, the new one is based on the direct detection of two-mode squeezed vacuum at the output of a traveling wave OPA. However, in the new method, one measures the difference-photocurrent variance rather than the correlation function of photocurrents (number of coincidences), which makes the technique applicable for high-gain OPA. In this work we test the new method versus the traditional one for the case of photon-counting detectors where both techniques are valid. </jats:p
