Robust Free Space Quantum Key Distribution

Secure space communications is essential for maintaining command and control of NASA and commercial satellites and for protection of sensitive data. As the computer speed and the technological capabilities available to hackers continues to increase, it is becoming increasingly difficult to protect and secure information. Current space communication cryptography protocols rely on the computational difficulty in factoring very large integers. However this will be an easy task when quantum computers become available. Then quantum key distribution (QKD) protocols, which are verifiably and unconditionally secure even under quantum computer attack, will be needed. In QKD, a cryptography key determined by random quantum states in photons is transmitted from the sender to the receiver. If an eavesdropper detects the photon states, the act of measurement changes the states in such a way that the sender and receiver can verify that the message has been compromised. Thus the sender simply waits until a key is transmitted without third party detection and then uses it to code the sensitive data which is consequently sent over a conventional communications channel. The goal is to show the feasibility of secure free space quantum communications in a noisy environment with sunlight and air turbulence.