Quantum cryptography system for a secure transmission of random keys using a polarization setting method
AssigneeDeutsche Telekom AG
InventorsWolfgang Dultz, Heidrun Schmitzer, Leonid Beresnev, Eric Hildebrandt
Life of this patent
Estimating the term…
Abstract
A quantum cryptography system using electrooptical liquid crystal modulators which change the polarization and which are designed as electrically rotatable retardation plates whose two birefringent axes are rotated by the applied electrical field around an angle θ which depends on the strength of this field. A λ/2 retardation plate rotates the elliptically polarized light striking the plate around an angle 2θ at speeds in the microsecond range. The quantum cryptography system can be used for interception-proof data transmission over transmission links that are accessible to the public.
Claims5
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 θ which depends on a strength of the applied electrical field, the electrically rotatable retardation plates being λ/2 retardation plates which rotate elliptically polarized light striking the λ/2 retardation plates around a second angle 2θ.
Dependencies are inferred from the claim text.