title: Full randomness from arbitrarily deterministic events.
abstract: Do completely unpredictable events exist? Classical physics excludes fundamental randomness. Although quantum theory makes probabilistic predictions, this does not imply that nature is random, as randomness should be certified without relying on the complete structure of the theory being used. Bell tests approach the question from this perspective. However, they require prior perfect randomness, falling into a circular reasoning. A Bell test that generates perfect random bits from bits possessing high-but less than perfect-randomness has recently been obtained. Yet, the main question remained open: does any initial randomness suffice to certify perfect randomness? Here we show that this is indeed the case. We provide a Bell test that uses arbitrarily imperfect random bits to produce bits that are, under the non-signalling principle assumption, perfectly random. This provides the first protocol attaining full randomness amplification. Our results have strong implications onto the debate of whether there exist events that are fully random.
authors.affiliation: 1] ICFO-Institut de Ciències Fotòniques, Mediterranean Technology Park, 08860 Castelldefels (Barcelona), Spain [2] Dahlem Center for Complex Quantum Systems, Freie Universität Berlin, 14195 Berlin, Germany.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Gallego
authors.forename: Lluis
authors.initials: L
authors.lastname: Masanes
authors.forename: Gonzalo
authors.initials: G
authors.lastname: De La Torre
authors.forename: Chirag
authors.initials: C
authors.lastname: Dhara
authors.forename: Leandro
authors.initials: L
authors.lastname: Aolita
authors.forename: Antonio
authors.initials: A
authors.lastname: Acín
mesh_terms: D006801:Humans; D010684:Philosophy; D011336:Probability; D011789:Quantum Theory; D013269:Stochastic Processes