The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 04, 2003
Filed:
Mar. 05, 1998
Applicant:
Inventor:
Paul D. Townsend, Ipswich, GB;
Assignee:
British Telecommunications public limited company, London, GB;
Attorney:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
H04L 9/00 ; G02B 2/608 ;
U.S. Cl.
CPC ...
H04L 9/00 ; G02B 2/608 ;
Abstract
A communication system uses quantum cryptography for the secure distribution of a key. A single-photon signal is phase-modulated and transmitted over a pair of time-multiplexed transmission paths. With each original single-photon signal in a given one of the transmission paths, a duplicate signal is transmitted. The duplicate is identically modulated and orthogonally polarized. At the receiver, the outputs of the two paths are combined interferometrically. A single polarization-insensitive measurement is derived from the combined contributions of the orthogonally polarized signals.