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Method and apparatus for free-space quantum key distribution in daylight

United States Patent

June 8, 2004
View the Complete Patent at the US Patent & Trademark Office
Los Alamos National Laboratory - Visit the Technology Transfer Division Website
A quantum cryptography apparatus securely generates a key to be used for secure transmission between a sender and a receiver connected by an atmospheric transmission link. A first laser outputs a timing bright light pulse; other lasers output polarized optical data pulses after having been enabled by a random bit generator. Output optics transmit output light from the lasers that is received by receiving optics. A first beam splitter receives light from the receiving optics, where a received timing bright light pulse is directed to a delay circuit for establishing a timing window for receiving light from the lasers and where an optical data pulse from one of the lasers has a probability of being either transmitted by the beam splitter or reflected by the beam splitter. A first polarizer receives transmitted optical data pulses to output one data bit value and a second polarizer receives reflected optical data pulses to output a second data bit value. A computer receives pulses representing receipt of a timing bright timing pulse and the first and second data bit values, where receipt of the first and second data bit values is indexed by the bright timing pulse.
Hughes; Richard J. (Los Alamos, NM), Buttler; William T. (Los Alamos, NM), Lamoreaux; Steve K. (Los Alamos, NM), Morgan; George L. (Jemez Springs, NM), Nordholt; Jane E. (Los Alamos, NM), Peterson; C. Glen (Los Alamos, NM), Kwiat; Paul G. (Champaign, IL)
The Regents of the University of California (Los Alamos, NM)
09/ 844,176
April 27, 2001
STATEMENT REGARDING FEDERAL RIGHTS This invention was made with government support under Contract No. W-7405-ENG-36 awarded by the U.S. Department of Energy. The government has certain rights in the invention.