How can we protect the confidentiality of a communication if we cannot trust the devices used to communicate?
Some physicians from IPhT (working with Docteur Nicolas Sangouard) Basel University and ETH Zurich University (working with Docteur Renato Renne) have contributed to answer this question and have petited for a patent. They have published an article in Physical Review Letters
Physical Review Letters Abstract:
Device-independent quantum key distribution provides security even when the equipment used to communicate over the quantum channel is largely uncharacterized. An experimental demonstration of device-independent quantum key distribution is however challenging. A central obstacle in photonic implementations is that the global detection efficiency, i.e., the probability that the signals sent over the quantum channel are successfully received, must be above a certain threshold.
We here propose a method to significantly relax this threshold, while maintaining provable device-independent security. This is achieved with a protocol that adds artificial noise, which cannot be known or controlled by an adversary, to the initial measurement data (the raw key). Focusing on a realistic photonic setup using a source based on spontaneous parametric down conversion, we give explicit bounds on the minimal required global detection efficiency.