With the (false) assumption that atoms possess their properties independently of measurements and independently of each other, a so-called Bell inequality can be derived. If it is violated by the results of an experiment, it follows that the properties of the atoms must be interdependent. This is described as Bell correlations between atoms, which also imply that each atom takes on its properties only at the moment of the measurement. Before the measurement, these properties are not only unknown - they do not even exist. A team of physicists from the University of Basel, along with colleagues from Singapore, have now observed these Bell correlations for the first time in a relatively large system, specifically among 480 atoms in a Bose-Einstein condensate. Earlier experiments showed Bell correlations with a maximum of four light particles or 14 atoms. The results mean that these peculiar quantum effects may also play a role in larger systems. http://phys.org/news/2016-04-atom-properties.html Paper: http://science.sciencemag.org/content/352/6284/441
Another quantum principle is that fundamental particles are identical, however a Bose-Einstein condensate is for all intents and purposes, a single aggregate particle. Its properties are different dependent on a number of factors. The number of identical individual particles making it up is only one dynamic. Very nice and remarkable experimental setup!
