  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 paper, 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. These remarkable
results were only made possible by the efficient implementation exploiting
hyperentanglement in the polarisation and energy-time degrees of freedom. We
provide a detailed characterisation of the gain in secure key rate achieved in
our proof-of-principle experiment at different noise levels. The results are
paramount for the implementation of a global quantum network linking quantum
processors and ensuring future-proof data security.
