Probability that the quantum world obeys local realism is less than one in a billion, experiment shows

Physicists have reported some of the strongest evidence yet that that the quantum world does not obey local realism by demonstrating new evidence for the existence of quantum entanglement. By performing an essentially loophole-free Bell test, they have shown that two atoms separated by a distance of a quarter of a mile share correlations that should be impossible under the hypothesis of local realism, and are most likely explained by quantum entanglement.

The new Bell test was performed by a group of researchers led by Harald Weinfurter at the Ludwig Maximilian University of Munich and the Max Planck Institute for Quantum Optics, both in Germany.

The probability that the observed correlations can be explained by local realism due to some unknown "hidden variables" rather than entanglement is less than one in a billion, the physicists write in their paper published in Physical Review Letters. By accounting for all of their accumulated data, taken over the course of seven months, that probability drops even further, down to about one intenquadrillion (the number 1 followed by 16 zeros). This means that the quantum world violates either locality (that distant objects cannot influence each other in less than a certain amount of time) or realism (that objects exist whether or not someone measures them), or possibly both.