A quantum heterodyne-detection system is described that affords K-ary phase-based digital communication at zero error probability at an average photon number of approximately K√3/2. In phase-based precision measurement—at the same average photon number—this system can measure an arbitrary c-number phase shift to within ±π/K rad with probability one.
© 1995 Optical Society of America
Jeffrey H. Shapiro, "Phase-conjugate quantum communication with optical heterodyne detection," Opt. Lett. 20, 1059-1061 (1995)