To build a global quantum communication network, low-transmission, fiber-based communication channels can be supplemented by using a free-space channel between a satellite and a ground station on Earth. We have constructed a system that generates hyperentangled photonic "ququarts" and measures them to execute multiple quantum communication protocols of interest. We have successfully executed and characterized superdense teleportation, a modified remote-state preparation protocol that transfers more quantum information than standard teleportation, for the same classical information cost, and moreover, is in principle deterministic. Our measurements show an average fidelity of 0.94±0.02, with a phase resolution of ∼7∘, allowing reliable transmission of >105 distinguishable quantum states. Additionally, we have demonstrated the ability to compensate for the Doppler shift, which would otherwise prevent sending time-bin encoded states from a rapidly moving satellite, thus allowing the low-error execution of phase-sensitive protocols during an orbital pass. Finally, we show that the estimated number of received coincidence counts in a realistic implementation is sufficient to enable faithful reconstruction of the received state in a single pass.
@article{arxiv.1901.07181,
title = {Time-bin and Polarization Superdense Teleportation for Space Applications},
author = {Joseph C. Chapman and Trent M. Graham and Christopher K. Zeitler and Herbert J. Bernstein and Paul G. Kwiat},
journal= {arXiv preprint arXiv:1901.07181},
year = {2020}
}