It was a pleasure to welcome Dr.Louise Wells, from Toshiba Europe Ltd, to the Cambridge Graphene Centre for the kick-off lecture of the QAMSS SRI Advanced Technology Lecture Series for Lent Term.
In her talk, titled Hybrid Photonic Integration for Quantum Key Distribution, Dr Wells presented recent advances in quantum photonic technologies, focusing on how hybrid integration can overcome key limitations in integrated quantum key distribution (QKD) systems. While integrated photonics has enabled rapid progress in QKD, material integration challenges, component losses, and the difficulty of integrating single-photon detectors continue to constrain system performance and scalability.
Dr Wells highlighted how hybrid photonic integration provides an effective solution to these challenges. By combining ultra-low-loss silicon nitride waveguides with indium phosphide electro-optic modulators, her work demonstrates high-performance QKD transceiver chips capable of bidirectional encoding and decoding of photonic qubits at GHz speeds, achieving sub-1% quantum bit error rates over long fibre distances.
The lecture also covered advances in single-photon detection, including the development of GHz-gated InGaAs/InP SPAD arrays with negligible inter-pixel crosstalk. When integrated with low-loss silica waveguide chips, these detectors enable compact hybrid QKD receivers. BB84 protocol experiments demonstrate secure key rates exceeding 2 Mbps at short distances and 15 kbps over 100 km of fibre.
This engaging lecture set an excellent tone for the Lent Term programme, launching a series of QAMSS talks that bring together cutting-edge research at the interface of quantum technologies and advanced materials.
