A quantum experiment has found that a phenomenon often described as “negative time” is more than an illusion, according to ScienceDaily. The work was published in Physical Review Letters and involved photons, or particles of light, passing through a cloud of rubidium atoms.
In the experiment, the photons could temporarily transfer energy to the atoms before continuing on. Researchers said that when a photon made it straight through the cloud, its average arrival time suggested it had spent a negative amount of time inside.
That idea has been discussed for decades, including in a 1993 experiment, but many physicists treated it as an artifact of how the light pulse was interpreted. Aephraim Steinberg of the University of Toronto, who was also involved in the earlier work, wanted to test what the atoms themselves would reveal.
To do that, the team used a weak laser to probe the atoms while the photon passed through, allowing them to estimate the dwell time without strongly disturbing the system. The researchers found that the weak measurement of dwell time matched the negative time inferred from the photon’s arrival, suggesting the effect is real within standard physics.
The researchers said the result does not point to a time machine, but it does show that the negative dwell time has a measurable effect on the atomic cloud the photon travels through.
