Quantum Networks: A Tale of Two Channels

July 20, 2020

Quantum Networks: A Tale of Two Channels

A quantum network uses photonic quantum states to connect quantum computers and sensors. Quantum networks promise to enable quantum versions of distributed computing, distributed sensing, secure cloud computing, and cryptography.

To build a global quantum network, there are two main ways to transmit the information: via fiber and free space. My graduate work focused on the free-space channel between a satellite and a ground station on the earth. We have constructed a system that generates entangled, photonic “ququarts” and measures them to execute multiple quantum communication protocols of interest in our laboratory. We successfully executed superdense teleportation and multiple quantum key distribution protocols, and we tested them both in lab-simulated conditions resembling the space-to-earth channel.

Another protocol of interest is entanglement swapping, necessary for building a quantum repeater network. I have designed and am constructing a system to implement entanglement swapping (and similar protocols such as quantum teleportation and measurement-device-independent QKD), which should be robust against the adverse effects of one entanglement source being in low-earth orbit and the other on the earth.

Future work will focus on addressing DOE’s interest in fiber-based quantum networks and develop a variable quantum buffer for synchronizing channels in a fiber-based network which drift due to environmental effects. Such a quantum buffer is imperative to the successful operation of many quantum networking protocols, including a standard quantum clock network and quantum repeaters, which the DOE and ORNL are focusing on currently.

About the Speaker: Joseph Chapman is a PhD student at the University of Illinois Urbana-Champaign, where he is leading an investigation to implement optical quantum communication in space for NASA.