Quantum Spatial Modulation of Optical Channels: Quantum Boosting in Spectral Efficiency

Spatial modulation (SM) improves spectral efficiency (SE) by creating the constellation of active optical antenna indices. However, quantum properties of light are not exploited to improve the SE. In this letter, multi-plane diffraction (MPD) set-up creating exponentially increasing number of propagation paths for classical sources is exploited to introduce quantum spatial modulation (QSM). Exponential number of paths and quantum superposition-based classical symbol generation for transmitting simultaneous multiple classical symbols are exploited for linear and exponential quantum boosting of SM, respectively. It is theoretically modeled, numerically analyzed, and the challenges of joint design of source-channel coding and QSM are discussed.