C3QS2018 Lecture "Event-ready loophole free Bell tests - From Foundations to Applications" Harald Weinfurter

Title

Event-ready loophole free Bell tests - From Foundations to Applications

Speaker

Harald Weinfurter, Professor, University of Munich, Germany

Abstract

An experimental test of Bell's inequality allows to test the validity of local-realistic descriptions of nature by measuring correlations between distant systems.  While such tests are conceptually simple, there are strict requirements concerning the detection efficiency of the involved measurements, as well as the enforcement of space-like separation between the measurement events. Only recently both loopholes could be closed simultaneously.

Here we present our approach based on combining heralded entanglement of atoms separated by 398 m with fast and efficient measurements of the atomic spin states. We obtain a violation S=2.22 +/ 0.033 > 2, which allows us to refute the hypothesis of local-realism with very high significance.

The mere fact that the existence of local hidden variables, i.e. inforamtion about the state, can be tested enables one to design protocols in quantum communication testing the existence of any possible information an eavesdropper could have about the communication. We discuss the benefits and requirements for the experiment of such so called device independent communication schemes.

The method to generate entanglement between remote quantum systems forms the core ingredient for quantum repeater. Starting from the present experiment, we also discuss the prospects and roadmaps towards future quantum networks.

This is a part of the workshop C3QS2018 organized by Quantum Systems Unit.  Everyone from OIST commuity is welcome!