Secure communications with low-orbit spacecraft using quantum cryptography

US5966224A · kind A · utility

Assignee

• The Regents of the University of California · US

Inventors

• Richard John Hughes · Los Alamos, US
• William T. Buttler · Los Alamos, US
• Paul G. Kwiat · Champaign, US
• Gabriel G. Luther · Los Alamos, US
• George L. Morgan · Jemez Springs, US
• Jane Elizabeth Nordholt · Los Alamos, US
• Charles Glen Peterson · Los Alamos, US
• Charles M. Simmons · Los Alamos, US

Key dates

• Filing date: May 20, 1997
• Grant date: Oct 12, 1999
• Expiry date: May 20, 2017

Classification

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

Abstract

Apparatus and method for secure communication between an earth station and spacecraft. A laser outputs single pulses that are split into preceding bright pulses and delayed attenuated pulses, and polarized. A Pockels cell changes the polarization of the polarized delayed attenuated pulses according to a string of random numbers, a first polarization representing a "1," and a second polarization representing a "0." At the receiving station, a beamsplitter randomly directs the preceding bright pulses and the polarized delayed attenuated pulses onto longer and shorter paths, both terminating in a beamsplitter which directs the preceding bright pulses and a first portion of the polarized delayed attenuated pulses to a first detector, and a second portion of the polarized delayed attenuated pulses to a second detector to generate a key for secure communication between the earth station and the spacecraft.