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We report on the generation of narrowband photon pairs at telecommunication wavelengths using a periodically poled lithium niobate waveguide that utilizes the nonlinear tensor element d(24) for type-II quasi phase matching. The FWHM bandwidth of the spontaneous parametric downconversion was 1 nm. The brightness of the photon pair source was ~6x10(5)/s/GHz(More)
We have realized a high-detection-efficiency photon number resolving detector at an operating wavelength of about 850 nm. The detector consists of a titanium superconducting transition edge sensor in an optical cavity, which is directly coupled to an optical fiber using an approximately 300-nm gap. The gap reduces the sensitive area and heat capacity of the(More)
We experimentally demonstrated preservation of indistinguishability between two photons via mode conversions, namely, photon-to-plasmon and plasmon-to-photon conversions. A two-photon interference experiment was carried out using a broadband photon pair generated through a spontaneous parametric downconversion process. We observed the so-called(More)
The most efficient modern optical communication is known as coherent communication, and its standard quantum limit is almost reachable with current technology. Though it has been predicted for a long time that this standard quantum limit could be overcome via quantum mechanically optimized receivers, such a performance has not been experimentally realized(More)
We have implemented the non-Gaussian operation on the pulsed squeezed vacuum at telecommunication wavelengths. The nonGaussian operation based on photon subtraction was carried out using a Titanium-based superconducting transition-edge-sensor that can resolve the photon number. We observed a dip in reconstructed Wigner functions of generated quantum states,(More)
We demonstrate a sub-shot-noise-limit discrimination of on-off keyed coherent signals by an optimal displacement quantum receiver in which a superconducting transition edge sensor is installed. Use of a transition edge sensor and a fiber beam splitter realizes high total detection efficiency and high interference visibility of the receiver and the observed(More)
High-order dispersion of long-range surface-plasmon-polariton waveguides (LR-SPP-WGs) have been investigated using a two-photon interferometer. Since linear and even-ordered dispersions in two-photon interferometry are cancelled out by a nonlocal quantum correlation, odd-ordered dispersions of millimeter-long LR-SPP-WGs are revealed. Even under the highly(More)
We have fabricated Niobium-based superconducting single photon detector (Nb-SSPD) for realizing high detection efficiency and fast reset time. The Nb-SSPD consisted of a 7 nm-thick and 200 nm-wide Nb meander line and exhibited the critical temperature and critical current density of 4 K and 4.6×10 A/cm, respectively. The Nb-SSPD was coupled to an optical(More)
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