Continuous Variable Quantum Encryption using Short Laser Pulses

The use of optical technology in both terrestrial and space-based wireless links has compelling advantages in terms of data rate, power consumption, weight, and size of the system. However, with the adoption of such technology, we have become heavily reliant on high data rate optical communication systems for our economy and national security. It is thus prudent to give careful consideration to the reliability, robustness to attack, and security of such data transmissions. Recently, a new method to protect the secrecy of optical transmissions against unauthorized eavesdropping has been proposed and demonstrated. This method, called AlphaEta, uses the quantum noise inherent in the light to create a highly secure physical layer encryption system which performs comparably, in terms of metrics such as ultimate propagation distance and sensitivity, to a conventional (unencrypted) system. We propose to augment an AlphaEta-like system by using a short pulse source to add the capability for spectral phase encoding and pulse-position modulation. These new properties can substantially increase the security of encryption, the sensitivity of the link, and the ability of such systems to be used for key generation.