Quantum system particles can be regenerated: “We made science fiction come true!” | Sciences

Imagine that you are 40 or older and you want to go on a date with the state you had 20 years ago. This is impossible in the classical material world. In quantum, the reference to the subatomic particles that underlie all reality, it is. These are the conclusions of a study by Spaniards Miguel Navasques and David Trillo, of the Institute for Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences (ÖAW), and the Experimental Physics Group of the University of Vienna. , to which the Austrian Philipp Walther belongs. Three theoretical investigations, published in X physical reviewAnd Quantum And arxivone accepted by Physical review letters And it has not yet been disclosed, and another experience, collected in opticsAnd proving that it is possible to “accelerate, slow down, and reverse the flow of time within random, even unsupervised, quantum systems”. These unique physical processes, capable of disrupting the normal course of time, are universal: they have the same effect on all particles, regardless of their nature and the way they interact with other systems.

Everything we perceive responds to the laws we learn in school, however, all researchers of quantum physics agree that they do not explain the subatomic world, which constitutes all of reality at its most microscopic level. In this imperceptible universe, there are superpositions (a particle can be in one state, another or both states at the same time), entanglement (an effect on one particle immediately affects the other, even if they are separated by great distances), or Teleportation.

This irrational reality in the face of the concrete is now joined by the ability to renew, to return to the previous state, as the Austrian and Spanish teams showed. Miguel Navasques resorts to an analogy and a comprehension to understand the discovery and the experience that illustrates this: “In the cinema [la física clásica]The film is shown from beginning to end, regardless of the will of the audience. at home [en el mundo cuántico], the remote control gives us the ability to manipulate the progress of the movie. We can go back to a previous scene or skip several scenes forward.”

The ÖAW team developed a “return protocol” that allows any particle (an electron, proton, or muon, for example) to return to its previous state. They have shown this theoretically, especially thanks to the work of Trillo, who found a fundamental key to solving the problem, according to Navascués, and experimentally, on a photon that evolves when passing through glass. An imaginative use of an experimental device known as a “quantum switch” allows a particle of light to return to the state it was in at the beginning of its journey.

“It was one of the most difficult experiments we’ve ever created for a single photon,” says Walter. And the Austrian physicist adds: “What’s incredibly interesting is that [las partículas] They can return to a state you don’t even know about,” that is, “it can be performed without knowing the system, its internal dynamics, or even the details of the interaction between the system and the experimenter,” the researchers explain.

The experiment begins, according to Navascués, from a century-old approach to Einstein’s theory of relativity: “The twin travels into space very quickly, while his brother stays on Earth. When the first flight returns, it will be less old than the one that stayed here and the navigator will confirm that the flight did indeed take less time than measured on Earth.As explained in one of the published investigations, this relativistic phenomenon, while observable, is “extremely impractical—huge amounts of energy or proximity to a black hole are needed to observe important—and limited—effects. They can be used to slow down the flow of time, but not to reverse or speed it up.”

But the Spanish physicist’s team wanted to show that “these limitations disappear when the realm of classical relativistic physics is abandoned and one enters the realm of non-relativistic quantum mechanics.”

And they succeeded, as the paper’s authors explain: “We introduce a global mechanism that acts on any qubit, propagating it to the state it was in before the experiment started.” Unlike protocols previously discovered by the group, which only work with a certain probability, the new mechanism always succeeds, except when the experimental device is completely “invisible” to the qubit. “This is how we answer the question whether such operations are allowed by the laws of quantum mechanics,” they say.

Can the experience be transferred to larger systems? The experiment is completed with particles that can store one piece of information. With a person, it is theoretically possible, but it is impossible and useless to put it into practice. If we had a person locked in a box, without any outside influence, that would theoretically be possible. But, with the protocols we have now, the probability of success is going to be very, very low. Moreover, the time it takes depends on the amount of information that the system can store, and a person, which is a physical system, contains a huge amount of information. It would take millions of years for this person to regenerate in less than a second. Does not make sense “.

Discovery is not a time machine. This also happens and it is the situation that changes. “In particles that are able to store one bit of information, the same amount of time you want to return the system that you have to use to work on it,” explains the physicist.

The same rule applies for particle aging, for condition improvement, for fast forward application to film. As Navascués explains, “If you want a system to be ten years old, you generally have to wait ten years. You can’t make time out of thin air: to make a system ten years old, say, one year, you have to get the nine years Remaining from somewhere. Following this hunch, the study authors came up with a trick that speeds up the passage of time. We discovered that evolutionary time can be transmitted between identical physical systems. In a year-long experiment with ten systems, one year could be stolen from each of the first nine systems All given to System X. At the end of the year, System X will be ten years old; the other nine will continue as they were when the experiment began.

The discovery is significant because it adds another specificity to the quantum realm, whose understanding of the true knowledge of the universe depends. But Philip Walther believes it also has practical consequences: “We are convinced that this also has technological applications. The rewind protocol can be used in quantum processors, for example, to reverse errors or unwanted developments.” “Additional follow-up investigations could include non-optical applications of the protocol, as well as extensions to higher dimensions,” the researchers add.

Navasques is not very optimistic, and has his doubts about the practical usefulness of the discovery. However, it is considered that the research conducted had unprecedented success. “We made science fiction come true!”

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