Sometimes science does things that seem to have been created after three coffees and a sleepless night. This is the case of two Austrian researchers, Miguel Navascués And Philip Waltherwho had an idea as bold as it was fascinating: using a quantum switch to manipulate time… at least for a photon.
No, no one is building a time machine. But what they observed is curious enough to make even those who don’t like particles, formulas and laboratories prick up their ears.
What is quantum switch
In the quantum world, the rules are different. Very different. Particles can be in two places together, influence each other from afar, and apparently do things that look dangerously like “rewinding” the time tape.
THE’quantum switch it is a device that allows a photon to perform two actions in two different orders… at the same time. It’s as if you could drink coffee before and after opening your eyes in the morning, at the exact same time. To us human beings it seems impossible, but for a particle it is routine.
And it is precisely thanks to this mechanism that the researchers observed something even more surprising: the photon, before completing its journey in the crystal, it had already returned to its previous state. A kind of built-in time “go back”.
The experiment
The idea arises from a key principle of quantum mechanics: observing a system changes it. Thus, Navascués and Walther decided to use this limitation as an opportunity. They sent a photon through a crystal, connected it to the quantum switch, and then analyzed its behavior. The result? Even before completing the journey, the photon was “restored” to its initial state. As if he had pressed the rewind button himself.
Obviously it is not possible to replicate this dynamic on macroscopic objects: reversing time by just one second would require millions of years of calculationssomething beyond even the most advanced computers. So no time jumps, no alternative versions of ourselves. But…
Because all this is important
The real goal of the research is not to send humans to revisit dinosaurs, but to solve one of the biggest problems of quantum computers: calculation errors.
If a wrong interaction could be “reversed” to its previous state — just as happens in the photon in the experiment — we would have infinitely more effective correction mechanisms. And this would pave the way for a new generation of much more reliable quantum technologies.
It’s as if the system were saying: “Oops, I made a mistake. I’ll go back for a moment.” A kind of “CTRL+Z” of the subatomic world.
