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

US6748083B2 · kind B2 · utility

Assignee

• The Regents of the University of California · US

Inventors

• Richard John Hughes · Los Alamos, US
• William T. Buttler · Los Alamos, US
• Steve K. Lamoreaux · Los Alamos, US
• George L. Morgan · Jemez Springs, US
• Jane Elizabeth Nordholt · Los Alamos, US
• C. Glen Peterson · Los Alamos, US
• Paul G. Kwiat · Champaign, US

Key dates

• Filing date: Apr 27, 2001
• Grant date: Jun 8, 2004
• Expiry date: Jan 23, 2023

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04L9/0858
• WIPO field: Telecommunications
• WIPO sector: Electrical engineering

Abstract

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.