In experiments, scientists managed to return to the past several times.
It is possible that time is still reversible. And his so-called arrow, supposedly directed only in one direction - from the past to the future, can be turned. And thus "rewind" what has already happened in the opposite direction. For example, roll back the minced meat or press the toothpaste back into the tube.
Fantastic? Not exactly as it turned out. Russian physicists conducted experiments in which they essentially demonstrated something similar.
The research was supervised by Gordey Lesovik, head of the laboratory of physics of quantum information technologies at the Moscow Institute of Physics and Technology (MIPT), was assisted by Mikhail Suslov from MIPT, their co-authors were our compatriots - Andrey Lebedev, Valery Vinokur and Ivan Sadovsky, who work in scientific institutions in the USA and Switzerland. They reported the results together in Scientific Reports in an article with the intriguing title "The Arrow of Time and its Reversal on IBM Quantum Computer."
Explaining the meaning of experiments, scientists first cite an example of an electron hovering somewhere in the universe. They explain that at the initial moment of time we can roughly know where he is. The laws of quantum mechanics do not allow you to specify the location very accurately - quantum particles demonstrate uncertainty, they can be here and there at the same time. But there is a certain area of the most probable localization.
Further, since everything that exists, according to the second law of thermodynamics, tends from order to chaos, the location of the electron becomes more and more uncertain. It seems to be spreading in different directions. As predicted by the Schrödinger equation, it is fundamental to quantum mechanics.
Unusual effects of the quantum world (says physicist Gordey Lesovik):
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Using the same equation, one can imagine how the "spread out" electron returns to its original place - it is localized in the same time that it spread out.
Lesovik and his colleagues illustrate the essence of quantum metamorphosis that occurs with an electron and billiard balls. Like, here they are - collected in a pyramid, then randomly roll out on the table and suddenly, obeying some mysterious force, they re-assemble into an ordered structure - in the same pyramid in the same place. These are the processes that scientists have modeled using a quantum computer.
Qubits - the elementary computing modules of a quantum computer - can be in three states: "0", "1", and uncertainty - "?" on the diagram. At the beginning of one of the experiments, scientists brought three qubits into the "0 0 0" state. This corresponded to the order - such that the electron would be localized, and the pyramid of balls would be collected.
Obeying some evolutionary program, the order in the state of the qubits was soon disrupted. This corresponded to the spreading of an electron and the collapse of a pyramid of balls.
Moments later, the same evolutionary program that caused chaos, surprisingly, began to put the state of the qubits in order. And they, in the end, returned to the past - to the previous state.
Experiment scheme: from order to chaos and back.
The time reversal trick did not work every time. In more "primitive" experiments - with two qubits - about 80 percent of them went from order to chaos and back. Three qubits showed this in about half the time.
Will such “turns” lead to the creation of a time machine? Physicists do not dare to assume this. But who knows, what if? A start seems to have been made.
Gordey Lesovik, Doctor of Physical and Mathematical Sciences:
VLADIMIR LAGOVSKY