Rupert Ursin

High-quality, distributed quantum entanglement is the distinctive resource for quantum communication and forms the foundation for the unequalled level of security that can be assured in quantum key distribution. While the entanglement provider does not need to be trusted, the secure key rate drops to zero if the entanglement used is too noisy. In this work, we show experimentally that QPA is able to increase the secure key rate achievable with QKD by improving the quality of distributed entanglement, thus increasing the quantum advantage in QKD. Beyond that, we show that QPA enables key generation at noise levels that previously prevented key generation. We provide a detailed characterisation of the gain in secure key rate achieved in our proof-of-principle experiment at different noise levels. The use of hyperentanglement in the field-tested polarisation and energy-time degrees of freedom enhances the efficiency of our scheme, making it an attractive option for deployment in high-loss regimes.