Experimental demonstration of Gaussian protocols for one-sided device-independent quantum key distribution
Sara Hosseini, The Australian National University
Nonlocal correlations, which was a longstanding foundational topic in quantum information, have recently found application as a resource for cryptographic tasks where not all devices are trusted. For example, the asymmetric phenomena of Einstein-Podolsky-Rosen steering plays a key role in one-sided device-independent quantum key distribution (1sDI-QKD) protocols. In the context of continuous-variable (CV) QKD, we identify all Gaussian protocols that can be 1sDI and calculate their maximum loss tolerance. Surprisingly, this includes a protocol that uses only coherent states. We also establish a direct link between the relevant EPR steering inequality and the secret key rate, further strengthening the relationship between these asymmetric notions of nonlocality and device independence. We experimentally implement both entanglement-based and coherent-state protocols, and measure the correlations necessary for 1sDI key distribution up to an applied loss equivalent to 7.5 km and 3.5 km of optical fibre transmission respectively.