Two-stage interferometer (IMAGE) Universitaet Stuttgart Caption In the Barz group’s experiment with a two-stage interferometer auxiliary photons are used to generate distinct measurement patterns for all four Bell states, increasing the efficiency beyond the traditional limit of 50%. Credit Jon Heras, Cambridge Illustrators Usage Restrictions no restriction License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.