Patent ID: 6748081
Filing Date: 2004-06-08
Classification: C09K,G02F,H04L

Abstract:
A quantum cryptography system for a secure transmission of random keys utilizing a polarization setting method, comprising:a quantum channel; a transmitting arrangement generating statistical binary number sequences which change a polarization of individual photons, the transmitting arrangement transmitting the binary number sequences via the quantum channel; a receiving arrangement analyzing the polarization and counting the individual photons; and electrooptical liquid crystal modulators changing the polarization, the liquid crystal modulators including electrically rotatable retardation plates having two birefringent axes which define an indicatrix, the birefringent axes being rotated by an applied electrical field around a first angle &thgr; which depends on a strength of the applied electrical field, the electrically rotatable retardation plates being &lgr;/2 retardation plates which rotate elliptically polarized light striking the &lgr;/2 retardation plates around a second angle 2&thgr;.