Abstract
Quantum mechanics predicts the existence of intrinsically random processes. Contrary to classical randomness, this lack of predictability can not be attributed to ignorance or lack of control. Here we find the optimal method to quantify the amount of local or global randomness that can be extracted in two scenarios: (i) the quantum steering scenario, where two parties measure a bipartite system in an unknown state but one of them does not trust his measurement apparatus, and (ii) the prepare-and-measure scenario, where additionally the quantum state is known. We use our methods to compute the maximal amount of local and global randomness that can be certified by measuring systems subject to noise and losses and show that local randomness can be certified from a single measurement if and only if the detectors used in the test have detection efficiency higher than 50%.
Highlights
This content has been downloaded from IOPscience
We use our methods to compute the maximal amount of local and global randomness that can be certified by measuring systems subject to noise and losses and show that local randomness can be certified from a single measurement if and only if the detectors used in the test have detection efficiency higher than 50%
We observe that the lower bound on the amount of global randomness that can be extracted in the steering scenario presented in [14] is tight
Summary
By analysing the data obtained in experiments involving local measurements on bipartite entangled systems one can prove that no one could have predicted this data in advance whenever a Bell inequality violation is observed [3, 4] This is called device-independent (DI) randomness certification [5, 6]. The main result of our paper is a general and optimal method to quantify the amount of local or global randomness that can be certified from a single measurement in a steering experiment. This is relevant, for instance, when the provider of a quantum-random-number generator wants to remotely check if the devices they provided are still functioning properly
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