Patent ID: 8433200
Filing Date: 2013-04-30
Classification: H04B,H04L

Abstract:
1. A method for quantum key delivery, comprising the steps of: preparing a nonlinear optical medium responsive to excitation light entered to produce pairs of quantum correlated photons based on spontaneous parametric fluorescence, each pair including a signal photon and an idler photon, and responsive to auxiliary signal light entered to produce auxiliary idler light based on a stimulated parametric conversion process; entering the excitation light and the auxiliary signal light simultaneously into the nonlinear optical medium; separating output light from the nonlinear optical medium into a signal light component, an idler light component and an auxiliary idler light component to direct and output the components to respective branching optical paths; when the signal light component and the auxiliary idler light component are entered, producing a first control signal for adjusting at least one of values of intensity and/or wavelength of the excitation light, and temperature of the nonlinear optical medium such that a ratio in intensity of the auxiliary idler light component to the auxiliary signal light component becomes substantially equal to a predetermined value, and producing a first electrical auxiliary idler signal converted from the auxiliary idler light component; when the idler light component and the auxiliary idler light component are entered, producing a second control signal for adjusting at least one of the values of the intensity and/or wavelength of the excitation light, and the temperature of the nonlinear optical medium such that the ratio becomes substantially equal to the predetermined value, and producing a second electrical auxiliary idler signal converted from the auxiliary idler light component; using at least one of the first and second control signals to adjust the at least one value to thereby maintain the ratio; and extracting clock signals from the first and second electrical auxiliary idler signals, and converting, in synchronism with the clock signals, the signal light component and the idler light component to a corresponding electrical reception signal and a corresponding electrical idler signal, respectively.