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National Laboratory for Ultrafast and Ultraintense Optical Science (ULTRAS),

CEWQO 2007. Central European Workshop on Quantum Optics 2007 14th Edition, 1-5 June 2007, Palermo, Italy. MARIA BONDANI. National Laboratory for Ultrafast and Ultraintense Optical Science (ULTRAS), C.N.R.-I.N.F.M. – COMO – Italy. Experimental demonstration of

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National Laboratory for Ultrafast and Ultraintense Optical Science (ULTRAS),

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  1. CEWQO 2007 Central European Workshop on Quantum Optics 2007 14th Edition, 1-5 June 2007, Palermo, Italy MARIA BONDANI National Laboratory for Ultrafast and Ultraintense Optical Science (ULTRAS), C.N.R.-I.N.F.M. – COMO – Italy Experimental demonstration of sub-shot-noise intensity correlations in an intense twin-beam A. Allevi, G. Zambra, A. Andreoni M.G.A. Paris J. Peřina, J. Křepelka, J. Peřina jr

  2. Outline • Introduction • Parametric downconversion • Experimental generation of intense twin-beam of light • Demonstration of non-classical correlations • Production of conditional states • Conclusion and future perspectives

  3. Introduction Parametric downconversion is the most important tool for the generation of entangled states Two different regimes are well explored: - single photon regime low-gain travelling-wave parametric amplifiers P. Kwiat et al. (1995) - continuous-variable regime parametric oscillators C. Schwob et al. (1997) A. Heidmann et al. (1987) J. Gao et al. (1998). seeded parametric amplifiers O. Aytür and P. Kumar (1990). D. T. Smithey et al. (1992). generation of intense twin-beam in a high-gain OPA

  4. Twin beam Single-mode bilinear interaction Hamiltonian acting on the vacuum originates the bipartite entangled state Conservation law Photon number distribution Twin-beam exhibit perfect quantum correlations in the photon number for any mean photon value

  5. We explore the high photon-number regime per mode by direct measurement of the photon number Intense twin beam Experimental production of intense twin beam must face noise in the generation and detection processes A. Agliati et al. (2005) Direct verification of quantum correlation in the photon number is a challenging task

  6. Experimental setup Pump field : Nd:YLF laser mode-locked reg. amp. 500 Hz rep rate 4.45 ps 349 nm Twin beam : signal @ 632.8 nm idler @ 778.2 nm Nonlinear crystal : b-BaB2O4 crystal (BBO I) 38.4 deg cut angle 11 cm2 cross-section 4 mm thickness Detectors : amplified p-i-n photodiodes detection efficiency 0.55 M. Bondani, A. Allevi, G. Zambra, M.G.A. Paris, A. Andreoni, Phys. Rev. A, in press

  7. Spatial coherence Angular bandwidth of the interaction speckle-like pattern To approach single-mode description we select a single pair of coherence areas on signal and idler by two apertures of suitable size. Note that Develop an effective model for the dependence of the size of the coherence areas on the parameters of the interaction A. Joobeur et al. (1996) A. Allevi et al. (2006)

  8. Temporal coherence Temporal bandwidth of the interaction multithermalmarginal distributions of the detected photons We assume that all the m modes are equally populated. L. Mandel and E. Wolf (1995) We expect the same number of modes on signal and idler

  9. Intensity correlations The existence of strong intensity correlations is necessary but not sufficient to assess entanglement. High correlation indicates the correct selection of the coherence areas. A. Agliati et al. (2005) A. Allevi et al. (2006)

  10. Nonclassicality Difference photocurrent is a marker of nonclassicality N = mean photon number For h = 0.55 To be compared with holding for bipartite coherent and thermal states A. Agliati et al. (2005)

  11. Sub-shot noise shot-noise value : noise reduction : Nonclassical regime (R = 0.47)

  12. Conditional state generation conditional distribution noise reduction of dB below the single-beam shot-noise level. The probability of success, i.e. the fraction of data that are kept to build the distribution is 0.22%. J. Laurat et al. (2003)

  13. Joint signal-idler photon-number distribution From experimental data for detected photons, we can reconstruct the joint photon-number distribution J. Peřina and J. Křepelka (2005). J. Peřina and J. Křepelka (2006).

  14. s = 0.2 s = 0.1 Joint signal-idler quasi-distributions of integrated intensities J. Peřina, J. Křepelka, Jan Peřina jr, M. Bondani, A. Allevi, A. Andreoni, in preparation

  15. Conclusions and perspectives • - direct detection of intensity can be used for demonstrating • sub-shot-noise intensity correlations in a ps-pulsed mesoscopic • twin-beam • proper selection of the twin coherence areas on the parties of • the twin-beam is necessary • the system allows us to demonstrate conditional generation of • sub-Poissonian light • - reduction of the experimental noise • in the detection, to decrease detected photons • in the generation, to increase detected photons

  16. Direct detection Real photodetector: ideal photodetector + beam splitter (t=h<1) BS: t=h ideal photodetector amplification Detected-photon statistics  photon statistics

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