Self-Testing Entangled Measurements in Quantum Networks

Phys Rev Lett. 2018 Dec 21;121(25):250507. doi: 10.1103/PhysRevLett.121.250507.

Abstract

Self-testing refers to the possibility of characterizing an unknown quantum device based only on the observed statistics. Here we develop methods for self-testing entangled quantum measurements, a key element for quantum networks. Our approach is based on the natural assumption that separated physical sources in a network should be considered independent. This provides a natural formulation of the problem of certifying entangled measurements. Considering the setup of entanglement swapping, we derive a robust self-test for the Bell-state measurement, tolerating noise levels up to ∼5%. We also discuss generalizations to other entangled measurements.