Canadian physicists at the University of Toronto have experimentally confirmed the existence of a measurable negative time delay for photons passing through rubidium atoms, reports infohub.kz.
A research group led by Ephraim Steinberg has demonstrated the reality of negative time delay for quantum particles. The results, published in Physical Review Letters, show that photons interacting with a cloud of rubidium atoms can exit it before entering.
In the experiment, scientists sent single photons through an atomic cloud. To measure the time a particle spends in the medium without destroying its state, they used weak measurements. They directed an additional low-power laser beam through the atoms, recording changes in its phase upon excitation of the elements.
Analysis of millions of measurements showed that the atoms remained in an excited state for a negative time. The authors emphasize that the result is fully consistent with quantum mechanics and does not violate causality, but it confirms the unusual properties of light-matter interaction.