title: Bell violation using entangled photons without the fair-sampling assumption.
abstract: The violation of a Bell inequality is an experimental observation that forces the abandonment of a local realistic viewpoint--namely, one in which physical properties are (probabilistically) defined before and independently of measurement, and in which no physical influence can propagate faster than the speed of light. All such experimental violations require additional assumptions depending on their specific construction, making them vulnerable to so-called loopholes. Here we use entangled photons to violate a Bell inequality while closing the fair-sampling loophole, that is, without assuming that the sample of measured photons accurately represents the entire ensemble. To do this, we use the Eberhard form of Bell's inequality, which is not vulnerable to the fair-sampling assumption and which allows a lower collection efficiency than other forms. Technical improvements of the photon source and high-efficiency transition-edge sensors were crucial for achieving a sufficiently high collection efficiency. Our experiment makes the photon the first physical system for which each of the main loopholes has been closed, albeit in different experiments.
authors.affiliation: Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Boltzmanngasse 3, Vienna 1090, Austria. marissa.giustina@univie.ac.at
authors.forename: Marissa
authors.initials: M
authors.lastname: Giustina
authors.forename: Alexandra
authors.initials: A
authors.lastname: Mech
authors.forename: Sven
authors.initials: S
authors.lastname: Ramelow
authors.forename: Bernhard
authors.initials: B
authors.lastname: Wittmann
authors.forename: Johannes
authors.initials: J
authors.lastname: Kofler
authors.forename: Jörn
authors.initials: J
authors.lastname: Beyer
authors.forename: Adriana
authors.initials: A
authors.lastname: Lita
authors.forename: Brice
authors.initials: B
authors.lastname: Calkins
authors.forename: Thomas
authors.initials: T
authors.lastname: Gerrits
authors.forename: Sae Woo
authors.initials: SW
authors.lastname: Nam
authors.forename: Rupert
authors.initials: R
authors.lastname: Ursin
authors.forename: Anton
authors.initials: A
authors.lastname: Zeilinger