Fidelity Bounds for Device-Independent Advantage Distillation

Understand

It is known that advantage distillation (that is, information reconciliation using two-way communication) improves noise tolerances for quantum key distribution (QKD) setups.

• Two-way communication is hence also of interest in the device-independent case, where noise tolerance bounds for one-way error correction are currently too low to be experimentally feasible.
• Existing security proofs for the device-independent repetition-code protocol (the most prominent form of advantage distillation) rely on fidelity-related security conditions, but previous bounds on the fidelity were not tight.
• We improve on those results by developing an algorithm that returns arbitrarily tight lower bounds on the fidelity.