Faster-than-light photons challenge the order of time

The fact that quantum physics deals with phenomena that might seem strange to classical physics has provided us with another example that might seem strange: A recent experiment showed that some photons Also known as particle waves of light It takes negative time to pass through a cloud of atoms.

In the study, which has not yet been peer-reviewed, researchers led by Daniela Ângulo from the University of Toronto (UofT) in Canada claim to have observed photons exiting an ultra-cold rubidium cloud before entering it. A team of scientists has detected signs of adverse weather conditions for the first time.

Co-author of the study, physicist Aephraim Steinberg, also of UofT, congratulated !” The work is hosted on the arXiv.org preprint server.

How is negative time delay measured?

When Steinberg talks about a positive time to complete the experiment, he specifically mentions 2017, when he and his labmate named Josiah Sinclair became interested. by a physics phenomenon known as atomic excitationeven during his Ph.D.

Atomic excitation occurs when atoms capture photons, causing their electrons to jump to higher energy levels. When these excited electrons return to their original state, they release the absorbed energy in the form of photons. This process of absorption and re-emission can cause a delay in the propagation of light through the material.

The result of this is an apparently lower group speed. faster than the speed of light in vacuum. It was this delay that Sinclair’s team wanted to measure, to define what happens to individual photons passing through the atomic cloud: Do they get dispersed and absorbed within the atomic cloud, or do they pass directly through the cloud without any interaction?

Testing photon delays in the laboratory

Sinclair told Scientific American that in 2017, the two friends began asking their advisors about the reason for the delay. “But the more people we interviewed, the more we realized that while everyone has their own intuition or hunch, there is no expert consensus on what the right answer is,” he said.

Realizing the counterintuitive nature of these delays, the team developed a device to test the problem in the laboratory three years later. The idea was to shoot photons through a cloud of ultracold rubidium atoms and measure the resulting degree of atomic excitation.

The authors had two surprises about the experiment: First, sometimes the photons passed through intact, but still, rubidium atoms became excited as if they had absorbed light particles.

But the strangest thing would come next, when the photons were absorbed, the rubidium atoms re-emitted almost instantly before returning to their ground state. It was as if the photons were leaving the atoms faster than expected.

How will the negative concept of time affect our experience?

In a press release, the researchers note that the results of the experiment “suggest that the negative values ​​assumed by moments such as group delay have greater physical significance than is generally appreciated.”

But as extraordinary as the evidence of “negative time” sounds is, they think the photons involved in the experiment do not contain information or properties that directly challenge our current understanding of time. In other words, This does not affect the fundamental understanding of time and how photons behave with respect to time. special theory of relativity.

Although the concept of time remains unchanged for us, the negative time delay observed in the behavior of photons may influence future research into understanding fundamental aspects of quantum physics.

Stay up to date on the latest quantum physics work at TecMundo. If you wish, take advantage of learning about tachyons, which are particles faster than the speed of light. Until later!