The Experiment Used Photons Passing Through a Cloud of Rubidium Atoms, Where the Photon's Energy Can Temporarily Excite the Atoms

A new experiment shows that photons can emerge from a cloud of atoms so early they appear to have spent negative time inside, and the atoms themselves confirm the effect. Researchers made extremely weak measurements of rubidium atoms to avoid disturbing the system, and the results corroborate the negative dwell time. The finding, published in Physical Review Letters, does not break standard physics but proves a strange quantum effect is physically measurable.

The experiment used photons passing through a cloud of rubidium atoms, where the photon's energy can temporarily excite the atoms. Due to Heisenberg's uncertainty principle, the photon's timing is uncertain, allowing it to appear to exit before entering. This effect was known since a 1993 experiment, but physicists dismissed it as an artifact.

Aephraim Steinberg, a co-author of that paper, revisited the question with a weak laser beam to probe the atoms without disturbing them. The atoms confirmed the negative time, suggesting the effect is real, not just a pulse-shaping illusion. It was nothing.

In fact, it was less than nothing. Negative five years I dwelt with Calypso. How else could I have arrived home after only ten years? If you don't believe me, ask her.