CHARACTERIZATION STUDY OF QUANTUM CRYPTOGRAPHY (QC) BY USING ENTANGLED SOURCE

The main goal in Quantum Cryptography is high security and this can be achieved by using single photon sources. The present work is a theoretical analysis devoted to investigate the interference pattern of biphoton amplitude generated by spontaneous parametric down conversion (SPDC) in a nonlinear crystal (BBO) pumped by femtosecond optical pulses. We have studied the visibility as a function of optical path delay for different parameters, such as the crystal length, dispersion in non- linear crystal, pump pulse duration and chirp parameter. The best visibility can be obtained at crystal length of (1.5 mm) .The amplitude of two photons in nonzero dispersion is affected greatly by different crystal length. And the interference pattern is varying with pump pulse duration, the shorter pump pulse duration, the lower visibility (V), and at specific pulse duration the visibility increase with decrease crystal length (L).