Eneet Kaur

Conditional mutual information-based measures such as intrinsic information and squashed entanglement have been important theoretical tools to obtain upper bounds on distillable secret-key rates, with the latter playing an important role for device-dependent quantum key distribution protocols. Inspired by this line of work, we propose an information-theoretic quantifier for Bell non-locality called intrinsic non-locality. It uses conditional mutual information to measure the deviation of a given bipartite correlation from one having a local-hidden-variable model. We prove that it satisfies certain desirable properties such as faithfulness, convexity, and monotonicity under local operations and shared randomness. Most especially, we then prove that intrinsic non-locality is an upper bound on the secret-key-agreement capacity of a large class of device-independent protocols conducted using a device characterized by a bipartite correlation. In other words, given a device characterized by such a bipartite correlation, the secret-key rate that can be extracted from this device with a device-independent protocol is bounded from above by intrinsic non-locality. Finally, we evaluate intrinsic non-locality to obtain an explicit bound on the secret-key rate that can be obtained from a specific bipartite correlation studied extensively in the device-independent literature.