Device-independent quantum key distribution with spin-coupled cavities

Understand

Device-independent quantum key distribution (DIQKD) guarantees the security of a shared key without any assumptions on the apparatus used, provided that the observed data violate a Bell inequality.

• Such violation is challenging experimentally due to channel losses and photo-detection inefficiencies.
• Here we describe a realistic DIQKD protocol based on interaction between light and spins stored in cavities, which allows a heralded mapping of polarisation entanglement of light onto the spin.
• The spin state can subsequently be measured with near unit efficiency.