Technologies for quantum routing*

Future quantum networks will require efficient routing of quantum information between nodes. However, quantum bits (qubits) cannot be measured and regenerated (as is standard in the classical internet) without altering the state. Thus it is necessary to develop technologies for routing photonic qubits in the optical domain without losing information. In addition, various approaches to entanglement sources, quantum processors, and other quantum network infrastructure may not be directly compatible, therefore requiring one or more transduction techniques to interconnect otherwise disparate devices. We present progress on several approaches to these challenges, including frequency shifting for transduction and quantum wavelength division multiplexing, polarization-qubit-preserving electro-optic switching, and ultrafast all-optical switching. We demonstrate frequency-shifting of ~5-ps telecom light pulses by up to ~2 nm (~240 GHz), and differential frequency-shifting of two 250-ps time-bins to realize time-bin "stacking". By decomposing arbitrary quantum states into the H-V basis, and switching each component separately, we demonstrate polarization-independent switching with >95% fidelity. Additionally, we achieve all-optical switching of single photons at 1590 nm at a rate of ~30 GHz with ~50% efficiency. These results mark important progress toward scalable, multi-node quantum networking.