Physicists using the SOLEIL synchrotron in France are the closest yet to realizing a thought experiment first proposed in 1927 by Albert Einstein. A variation on the much-loved double-slit experiment, the measurement confirms an aspect of quantum theory that Einstein had sought to discredit. The SOLEIL experiment uses two excited atoms in place of the two slits of Einstein's experiment and shows that when one can determine which atom has emitted an electron, a quantum interference pattern vanishes.

To read more, click here.