A team of physicists claims to have moved light from one side of time to the other simultaneously ; that is, a kind of quantum trick to move a photon (particle of light) forward and backward in time.

The quantum experiment in which a particle of light has traveled back and forth in time at the same time has been demonstrated by two independent research groups. Can a photon exist in both states of time at the same time?

### How have they achieved it?

The scientists involved in both experiments have achieved this thanks to a combination of two principles that are part of the strange world of quantum mechanics and using a special optical crystal: the convergence of quantum superposition and the symmetry of charge, parity and time reversal. (CPT), which describe the physical properties of atoms and subatomic particles.

Thanks to this effect, splitting a photon through a crystal produces a counterintuitive behavior or rule . The clearest example of quantum superposition we know from the hand of Schrödinger and the famous hypothetical cat that is considered both alive and dead due to the fact that its life is in the hands of a random subatomic event that takes place and has no place until observed. On the other hand, the second law, symmetry of charge, parity, and time reversal, states that any system containing particles will obey the same physical laws even if the charges, spatial coordinates, and motions through time of the particles are invest. This makes it possible for an overlapping particle to travel both forward and backward in time .

By measuring the polarization of the photons during the experiment, previously recombining the overlapping photons moving through another crystal, they found a quantum interference pattern: a pattern that could only and exclusively occur if the same photon moved in both directions. That’s right: a photon that seemed to travel simultaneously along and backward on the arrow of time .

If confirmed, as the studies are pending peer review and available on the arXiv preprint server, placing a particle of light in an overlay to travel both forward and backward in time could prove useful for computation. quantum (and not so much to allow us time travel, which is surely what many readers are thinking). And it is that it would not have an immediate practical use, but perhaps it would have implications for quantum computers, even helping to develop a theory of quantum gravity. We will soon know if this exotic physics experiment leads to new paths in quantum physics.

Time travel would be possible, but only in parallel time lines

Reference: Experimental superposition of time directions

Teodor Strömberg, Peter Schiansky, Marco Túlio Quintino, Michael Antesberger, Lee Rozema, Iris Agresti, Časlav Brukner, Philip Walther Quantum Physics

https://doi.org/10.48550/arXiv.2211.01283

Experimental demonstration of input-output indefiniteness in a single quantum device

Yu Guo, Zixuan Liu, Hao Tang, Xiao-Min Hu, Bi-Heng Liu, Yun-Feng Huang, Chuan-Feng Li, Guang-Can Guo, Giulio Chiribella Quantum Physics

https://doi.org/10.48550/arXiv.2210.17046