Scientists observe 'negative time' in quantum experiments

 

Experimental physicist Daniela Angulo poses with an apparatus in the physics lab at the University of Toronto.

Light can occasionally appear to leave a material before entering it, a phenomenon that scientists have long recognized as an illusion brought on by the distortion of waves by matter.

Through cutting-edge quantum tests, researchers at the University of Toronto claim to have shown that "negative time" is more than just a theoretical concept; it actually exists in a concrete, physical sense and merits further investigation.

The results, which have drawn both international notice and skepticism, were released on the preprint server arXiv but have not yet been published in a peer-reviewed publication.

The researchers stress that rather than indicating a fundamental change in how we perceive time, these puzzling findings point to a peculiarity of quantum mechanics.

"Even discussing this with other physicists is difficult. "We are frequently misunderstood," said Aephraim Steinberg, a professor of experimental quantum physics at the University of Toronto.

Although the idea of "negative time" may seem like something taken from science fiction, Steinberg argues for its application in the hopes that it will lead to more in-depth conversations about the enigmas of quantum physics.

Laser experiments

The group started investigating how light and matter interact years ago.

Some photons—light particles—are absorbed by atoms and then re-emitted after passing through them. The atoms are altered by this interaction, momentarily becoming "excited" or higher-energy before returning to their regular condition.

The goal of the study, which was headed by Daniela Angulo, was to determine how long these atoms remained in their excited condition. Steinberg clarified that "that time turned out to be negative," referring to a length that was less than zero.

Consider cars entering a tunnel to illustrate this idea. Prior to the experiment, physicists realized that, although a thousand cars may reach the tunnel at noon on average, the first cars could leave a bit earlier, at 11:59 am, for example. Previously, this outcome was written off as meaningless.

Angulo and associates' demonstration was comparable to taking a reading of the tunnel's carbon monoxide levels after the first few cars appeared and discovering that the readings showed a negative sign.

Relativity intact

It took more than two years to refine the trials, which were carried out in a messy basement lab full with wires and gadgets coated in metal. Careful calibration of the lasers was necessary to prevent data from being distorted.

However, Steinberg and Angulo quickly explain that no one is asserting that time travel is possible. Steinberg remarked, "We don't want to say anything traveled backward in time," "That's a misinterpretation."

Quantum physics, which describes how particles like photons act in fuzzy, probabilistic ways rather than according to rigid rules, provides the explanation.

These interactions take place over a range of potential periods, some of which contradict common sense, rather than following a set timeframe for absorption and re-emission.

The researchers argue that this is crucial since it does not contradict Einstein's special relativity theory, which states that nothing can move faster than light. These photons avoided any cosmic speed constraints since they carried no information.

A divisive discovery

The idea of "negative time" has generated interest as well as skepticism, especially from well-known scientists.

In one YouTube video that was watched by more than 250,000 people, German theoretical physicist Sabine Hossenfelder criticized the work, saying, "The negative time in this experiment has nothing to do with the passage of time—it's just a way to describe how photons travel through a medium and how their phases shift."

Angulo and Steinberg resisted, claiming that their study fills important knowledge gaps about why light doesn't always move at the same pace.

Although Steinberg acknowledged the criticism surrounding the provocative headline of their paper, they noted that the experimental results have not been contested by any respectable scientists.

He stated, "We've made our choice about what we think is a fruitful way to describe the results," and that although real-world uses are still a ways off, the discoveries provide new opportunities to study quantum processes.

"I'll be honest, I don't currently have a path from what we've been looking at toward applications," he said. "We're going to keep thinking about it, but I don't want to get people's hopes up."

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