Towards optical quantum communication in space
"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. To this end, we have developed a system that generates hyperentangled photonic ""ququarts'' and measures them to execute multiple quantum communication protocols of interest, including superdense teleportation and high-dimensional entanglement-based quantum key distribution (QKD). To this same end, we also have developed another system to execute entanglement swapping, a protocol required for a fully functional quantum network, while in orbit. Our characterization of SDT shows an average fidelity of 0.94+\-0.02, with a phase resolution of ~7 degrees, allowing reliable transmission of >100,000 distinguishable quantum states. We also demonstrated the ability to compensate for the Doppler shift from satellite motion and simulated the event rate in a satellite-to-Earth implementation. Additionally, we implemented an entanglement-based QKD protocol developed by Bennett, Brassard, and Mermin in 1992 (BBM92), achieving quantum bit error rates (QBER) below 2%. More importantly, we demonstrate low QBER execution of a higher dimensional hyperentanglement-based QKD protocol that we developed and compared its performance directly to BBM92. Finally, we designed and have started constructing a system to implement an orbit-robust implementation of entanglement swapping. The detailed system engineering of the hardware involved is presented and preliminary results are discussed."
quantum communication, quantum entanglement, hyperentanglement, non-linear optics, quantum key distribution, superdense teleportation, quantum state tomography, spontaneous parametric down-conversion
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign