Secure Free-Space Optical Transmission of Y-00 Quantum Stream Cipher with 4096-Level Intensity Modulated Signals

A secure free-space optical (FSO) system using a Y-00 quantum stream cipher is proposed and error-free (BER<10-9) secure FSO transmission over 30 m is achieved with a real-time 1.5-Gb/s Y-00 cipher with 4096 intensity levels.