Adapting classical infrastructure for quantum networks: challenges and solutions

The development of quantum networks marks a transformative advance in communication technologies, enabling communication security unattainable through classical signals and the interconnection of quantum computers, sensors, and devices at various scales. Leveraging classical telecommunication infrastructure, such as optical fibers and associated devices, is pivotal for practical quantum network implementation. The Washington Metropolitan Quantum Network Research Consortium (DC-QNet) is developing a quantum network testbed in the Washington, DC area based on this infrastructure. However, adapting classical systems for quantum networks introduces significant challenges, including crosstalk between classical and quantum channels, stringent synchronization precision demands, polarization drift in optical fibers, and the limitations of classical optical devices. We present experimental demonstrations of these challenges and novel solutions, including a new crosstalk characterization technique. Results are derived from real-world DC-QNet infrastructure, showcasing the feasibility and progress of quantum network implementation.