Quantum channel with controllable decoherence using polarization-time coupling

An optical quantum channel that introduces decoherence in the polarization state by continuously controlling the output degree of polarization (DOP) is proposed, and a proof-of-principle experiment is performed. The decoherence is achieved by a depolarizing process that couples the polarization and time-of-flight degrees of freedom of the single photons in a high-birefringence medium, and is experimentally characterized via standard quantum state tomography. It is shown that the output DOP is independent of the input polarization state and the response times of the photodetectors.