Quantum physics showcases numerous bizarre phenomena and is often counterintuitive. This time, researchers recalled the film "Tenet" with their discovery, which can be referred to as negative time.
A yet-to-be-reviewed study published in Scientific American describes the observation of unusual temporal behavior of photons during the excitation of atoms. Photons directed at a cloud of atoms exited the medium before they entered it.
“Negative time delay may seem paradoxical, but it implies that if you were to create 'quantum' clocks to measure the duration that atoms remain in an excited state, the clock's hands would, under certain circumstances, move backward rather than forward,” explains Josiah Sinclair from the University of Toronto. His earlier experiments laid the groundwork for the research, although he was not directly involved in it.
Photons, the particles of light, can be absorbed by the atoms they pass through. When this occurs, the energy they carry causes the electrons in the atoms to shift to a higher energy state — this is known as excitation.
However, atoms can also shed this excitation and return to their normal state. One way this happens is through the emission of energy in the form of photons. To an observer, it appears as if the light passing through the medium is delayed. Scientists had no consensus on what actually happens to an individual photon during this delay, prompting them to conduct a series of experiments.
During these experiments, photon impulses were sent through a cloud of atoms at temperatures close to absolute zero. An odd phenomenon occurred: in cases where the photons passed through without being absorbed, the ultracold atoms were already excited for a precise interval, as if they had already absorbed them. Conversely, in cases where the photons were absorbed, they were re-emitted with no delay or before the ultracold atoms could release the excitation.
Researchers state that no laws of physics are being violated here. Somehow, photons travel through the atomic cloud faster when they excite atoms and are absorbed than when the atoms remain unchanged. Since photons carry no information, causality remains intact, the researchers note. Quantum superposition allows photons to exist in two states simultaneously: for a detector measuring when they enter and exit the medium, it means photons can have both positive and negative values, and consequently, effectively negative time.
This does not alter our understanding of time, according to the researchers. Rather, it suggests that at least in the realm of optics, negative time has "greater physical significance than previously believed," the study concludes.
Source: Futurism
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