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25 May 2005 Two-color parametric down conversion
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We propose a point to point quantum channel based on a two-color Spontaneous Parametric Down Conversion (SPDC), that may be applied for a Quantum Key Distribution (QKD) system to gain better security. We use one arm of the SPDC (770 nm - optimal for Si detection) and a Si counter at Alice's side to count the exact number of photons in each pulse. Whenever the arm contains exactly one photon, the correlated photon (1550nm - optimal for fiber transmission) in the other arm is sent via a fiber to Bob. In the experiment we used an Ar^{+} laser of 514.5nm wavelength and a BBO crystal to produce type-I photon pairs. We measured the spectrum of the SPDC and resolved specifically the 770 nm wavelength. The rate of correlated pairs (at 890-1050 nm) from our SPDC source was compared to a non-correlated source. We further developed an InGaAs single photon detector based on Geiger mode APD and achieved 10% quantum efficiency and 5 * 10^{-3} dark counts per 20nsec pulse at a temperature of -35 degrees Celsius.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
David Castiel, Adam De La Zerda, Alex Hayat, Matty Katz, Tal Mor, Meir Orenstein, Gil Ratsaby, and Nadav Yoran "Two-color parametric down conversion", Proc. SPIE 5815, Quantum Information and Computation III, (25 May 2005);

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