Practical Considerations for the Creation and Scaling of Quantum Networks

Abstract

Small-scale quantum networks have been around for a few years now, but more recently quan-tum networks have begun to scale to the size of Metropolitan networks. Certain practical consider- ations are necessary to scale these networks to multi-node networks over 10s–100s of kilometers. I will review the limitations of current quantum networks, including time synchronization, the necessity of deterministic efficient entanglement sources and issues with developing a quantum repeater. I will describe joint work on growing InAlAs/InP quantum dots using droplet epitaxy which resulted in highly symmetric quantum dots. Consequently, the fine structure splitting of these dots is likely reduced making them an ideal entangled pair source. Additionally, we describe the design and fabrication of circular Bragg gratings, which efficiently couple light from InAs/InP quantum dots, allowing us to measure the biexciton cascade. Additional research was conducted to distribute highly accurate time synchronization over 100s of kilometers using White Rabbit (High Accuracy Precision Time Protocol) and Electronic Stabilization protocols. Accuracies of sub-10 ps were achieved for intervals of 10^5 seconds. This effort also includes the characterization of DC- Qnet, covering time and polarization variations due to environmental fluctuations, as well as noise generated from classical signals. Finally, I will describe a plug and play QKD implementation on a small scale quantum network that incorporates time synchronization for both encoding qubits and synchronizing measurements. This time synchronization allows for stability of QBER to below 11% for at least 8 hours.