In an attempt to test quantum nonlocality — the “spooky interaction at a distance” that occurs between two entangled particles, physicists from the University of Geneva have sent two entangled photons traveling to different towns located 18 km apart –the longest distance for this type of quantum measurement.

By separating the two interferometer measurements by 18 km (a photon would take 60 microseconds to cover the 18 km), they were able to confirm that the quantum measurements (made simultaneously at each of the interferometers in just 7.1 microseconds) could not be been influenced by anything traveling at–or even a few times more than–the speed of light, thus ruling out any kind of classical communication between the two entangled particles separated by a distance.

The test once again confirms the nonlocal nature of quantum correlations.