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

In a groundbreaking twist that sounds like science fiction, researchers at the University of Toronto claim to have observed "negative time" in quantum experiments. While the idea might evoke images of time travel, the scientists insist this is no Hollywood plot—it’s a glimpse into the quirky world of quantum mechanics.

The findings, shared on the preprint server arXiv, suggest that the phenomenon, once dismissed as an illusion, might be real in a physical sense. Though the research has yet to undergo peer review, it’s already sparking global intrigue—and skepticism.

What is `negative time`?

Light, when interacting with matter, behaves in ways that often defy intuition. For decades, scientists noted peculiar phenomena where light seemed to exit a material before fully entering it. These were typically chalked up to distortions in wave behavior, but the new experiments argue otherwise.

"This is tough stuff, even for us to explain to other physicists," said Aephraim Steinberg, a quantum physics professor leading the study. "But we think it’s worth talking about because it sheds light on some deep mysteries of quantum mechanics."

The term "negative time" refers to a duration less than zero, a result that emerged from experiments led by PhD student Daniela Angulo. The team measured how long atoms stayed in an excited state after interacting with photons—light particles. Surprisingly, the data indicated a negative duration.

The tunnel analogy

Steinberg likened the concept to cars entering a tunnel. Imagine the average entry time for a thousand cars is noon. In rare cases, the first cars might appear to exit earlier, say at 11:59 a.m. While such results were once dismissed as statistical noise, Angulo’s team showed that these “negative times” could be reliably measured.

"This is like measuring carbon monoxide in the tunnel after the first cars leave and finding the levels have a minus sign in front of them," Steinberg explained.

Inside the experiments

The experiments took place in a basement lab filled with lasers, wires, and aluminum-wrapped devices. The team meticulously calibrated their equipment over two years to ensure accurate results.

But Steinberg is clear: this doesn’t mean time travel is on the horizon. “We’re not saying anything is traveling backward in time,” he emphasised. Instead, the results reflect the probabilistic nature of quantum mechanics, where particles like photons don’t follow fixed timelines.

Crucially, the findings don’t violate Einstein’s special relativity, which states that nothing can travel faster than light. The observed photons carried no information, avoiding any breach of cosmic speed limits.

Controversy and criticism

The study has drawn both fascination and criticism. Prominent physicist Sabine Hossenfelder described the results as a mathematical artifact rather than a physical phenomenon. "It’s just a way to describe how photons travel through a medium and how their phases shift," she noted in a YouTube video.

Angulo and Steinberg, however, defend their work, arguing that it sheds light on why light doesn’t always travel at a constant speed. “We’ve made our choice about how to describe the results,” Steinberg said, acknowledging the provocative nature of their paper’s title.

What’s next?

While practical applications remain elusive, the researchers believe their findings open doors to new quantum inquiries. “I’ll be honest, I don’t currently have a path from what we’ve been looking at toward applications,” Steinberg admitted. “But we’re going to keep thinking about it.”

For now, "negative time" remains a curious concept that deepens the mystery of quantum mechanics—a realm where intuition often takes a backseat to paradox.

Source: Phys.org