High-fidelity ghost diffraction and transmission in free space through scattering media

We report a different class of ghosts, called ghost diffraction and transmission with compressed spectrum coefficients, for ghost (e.g., analog-signal) transmission in free space through scattering media using a single-pixel detector. The ghost, e.g., analog signal, is first transformed to its spectral domain, such as Hadamard domain. The generated Hadamard spectrum coefficients can be flexibly compressed in order to reduce the number of random patterns to be illuminated and transmitted in free space, and the selected Hadamard spectrum coefficients are sequentially encoded into random amplitude-only patterns as information carriers. In the experiments, high-quality Hadamard spectrum transmission using a coherent light source is realized in different scattering environments, and, subsequently, high-fidelity ghosts are further retrieved from the received Hadamard spectrum coefficients. Experimental results demonstrate that the proposed method possesses high robustness against wave diffraction, multi-layer scattering, and noise. This class of ghosts provides a different insight about quantum and classical optics for analog-signal transmission in free space, and an avenue toward many applications, e.g., quantum ghost transmission and communication, could be opened up.