Fundamental limitations on device-independent quantum conference key agreement
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We provide several general upper bounds on device-independent conference key agreement (DI-CKA) against the quantum adversary. They include bounds by reduced entanglement measures and those based on multipartite secrecy monotones such as reduced cc-squashed entanglement. We compare the latter bound with the known lower bound for the protocol of conference key distillation based on the parity-CHSH game. We also show that the gap between DI-CKA rate and the rate of device-dependent is inherited from the bipartite gap between device-independent and device-dependent key rates, giving examples that exhibit the strict gap.
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