Computing conditional entropies for quantum correlations

Understand

The rates of quantum cryptographic protocols are usually expressed in terms of a conditional entropy minimized over a certain set of quantum states.

• In particular, in the device-independent setting, the minimization is over all the quantum states jointly held by the adversary and the parties that are consistent with the statistics that are seen by the parties.
• Here, we introduce a method to approximate such entropic quantities.
• Applied to the setting of device-independent randomness generation and quantum key distribution, we obtain improvements on protocol rates in various settings.