Evidence of ‘Negative Time’ Found in Quantum Physics Experiment

Quantum physicists are understandn with wonky, seemingly nonsensical phenomena: atoms and molecules sometimes act as particles, sometimes as waves; particles can be connected to one another by a “spooky action at a distance,” even over wonderful distances; and quantum objects can erase themselves from their properties appreciate the Chesemploy Cat from Alice’s Adventures in Wonderland erasees itself from its grin. Now researchers led by Daniela Angulo of the University of Toronto have discdisthink abouted another oddball quantum outcome: pboilingons, wave-particles of weightless, can spfinish a adverse amount of time zipping thraw a cdeafening of chilled atoms. In other words, pboilingons can seem to exit a material before go ining it.

“It took a preferable amount of time, but our experiment observing that pboilingons can produce atoms seem to spfinish a *adverse* amount of time in the excited state is up!” wrote Aephraim Steinberg, a physicist at the University of Toronto, in a post on X (establisherly Twitter) about the recent study, which was uploaded to the preprint server arXiv.org on September 5 and has not yet been peer-studyed.

The idea for this labor ecombined in 2017. At the time, Steinberg and a lab colleague, then doctoral student Josiah Sinclair, were interested in the conveyion of weightless and matter, definitepartner a phenomenon called atomic excitation: when pboilingons pass thraw a medium and get participateed, electrons swirling around atoms in that medium jump to higher energy levels. When these excited electrons lapse to their innovative state, they free that participateed energy as redisindictted pboilingons, introducing a time postpone in the weightless’s watchd transit time thraw the medium.

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Sinclair’s team wanted to meacertain that time postpone (which is sometimes technicpartner called a “group postpone”) and lacquire whether it depfinishs on the overweighte of that pboilingon: Was it scattered and participateed inside the atomic cdeafening, or was it sendted with no conveyion whatsoever? “At the time, we weren’t certain what the answer was, and we felt appreciate such a fundamental ask about someskinnyg so fundamental should be basic to answer,” Sinclair says. “But the more people we talked to, the more we authenticized that while everyone had their own intuition or guess, there was no expert consensus on what the right answer would be.” Becaparticipate the nature of these postpones can be so strange and counterperceptive, some researchers had written the phenomenon off as effectively uncomferventingless for describing any physical property associated with weightless.

After three years of arrangening, his team growed an apparatus to test this ask in the lab. Their experiments participated shooting pboilingons thraw a cdeafening of ultrafreezing rubidium atoms and measuring the resulting degree of atomic excitation. Two surpelevates ecombined from the experiment: Sometimes pboilingons would pass thraw unscathed, yet the rubidium atoms would still become excited—and for equitable as lengthy as if they had participateed those pboilingons. Stranger still, when pboilingons were participateed, they would seem to be redisindictted almost instantly, well before the rubidium atoms returned to their ground state—as if the pboilingons, on mediocre, were leaving the atoms speedyer than foreseeed.

The team then collaborated with Howard Wiseman, a theoretical and quantum physicist at Griffith University in Australia, to conceive an exarrangeation. The theoretical structurelabor that ecombined showed that the time these sendted pboilingons spent as an atomic excitation suited perfectly with the foreseeed group postpone acquired by the weightless—even for cases where it seemed as though the pboilingons were redisindictted before the atomic excitation had ebbed.

To understand the nonsensical discovering, you can skinnyk of pboilingons as the fuzzy quantum objects they are, in which any given pboilingon’s absorption and reeignoreion thraw an atomic excitation is not secured to occur over a certain repaired amount of time; rather, it gets place atraverse a smeared-out, probabicatalogic range of temporal cherishs. As showd by the team’s experiments, these cherishs can encompass instances when an individual pboilingon’s transit time is instantaneous—or, bizarcount on, when it ends before the atomic excitation has finishd, which gives a adverse cherish.

“I can promise you that we were finishly surpelevated by this foreseeion,” Sinclair says, referring to the suitup between the group postpone and the time that the sendted pboilingons spent as atomic excitations. “And as soon as we were self-promised we hadn’t made a misget, Steinberg and the rest of the team—I had shiftd on to do a postdoc at [the Massachusetts Institute of Technology] by this point—began arrangening to do a trail-up experiment to test this crazy foreseeion of adverse dwell time and see if the theory would helderly up.”

That trail-up experiment, the one led by Angulo that Steinberg touted on X, can be understood by pondering the two ways a pboilingon can be sendted. In one, the pboilingon wears blinders of sorts and disthink abouts the atom enticount on, leaving without even a nod. In the other, it conveys with the atom, raiseing it to a higher energy level, before getting redisindictted.

“When you see a sendted pboilingon, you can’t understand which of these occurred,” Steinberg says, grasping that becaparticipate pboilingons are quantum particles in the quantum authenticm, the two outcomes can be in superposition—both skinnygs can happen at the same time. “The measuring device finishs up in a superposition of measuring zero and measuring some petite preferable cherish.” But correactingly, Steinberg notices, that also uncomfervents that sometimes “the measuring device finishs up in a state that sees not appreciate ‘zero’ plus ‘someskinnyg preferable’ but appreciate ‘zero’ minus ‘someskinnyg preferable,’ resulting in what sees appreciate the wrong sign, a adverse cherish, for this excitation time.”

The meacertainment results in Angulo and her colleagues’ experiment propose that the pboilingons shiftd thraw the medium speedyer when they excited the atoms than when the atoms remained in their ground state. (The pboilingons aren’t communicating any alertation, so the outcome does not refuse the “noskinnyg can travel speedyer than weightless” speed restrict set by Einstein’s exceptional theory of relativity.)

“A adverse time postpone may seem paradoxical, but what it uncomfervents is that if you built a ‘quantum’ clock to meacertain how much time atoms are spfinishing in the excited state, the clock hand would, under certain circumstances, shift backward rather than forward,” Sinclair says. In other words, the time in which the pboilingons were participateed by atoms is adverse.

Even though the phenomenon is astonishing, it has no impact on our comfervent of time itself—but it does show once aacquire that the quantum world still has surpelevates in store.

“[Angulo] and the rest of the team have accomplished someskinnyg repartner amazeive and produced a pretty set of meacertainments. Their results elevate fascinating asks about the history of pboilingons traveling thraw absorptive media and necessitate a reexpoundation of the physical uncomferventing of the group postpone in chooseics,” Sinclair says.

A version of this article originpartner ecombineed in Spektrum der Wissenschaft and was reproduced with perignoreion.