Quantum simulation gives a sneak peek into the possibilities of time reversal — ScienceDaily

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We all use clocks and calendars to mark the days, but perhaps no clocks are more direct than mirrors. The changes we have noticed over the years vividly illustrate the “arrow of time” of science – the possible development from order to disorder. We can't reverse this arrow because we can eliminate all wrinkles or restore the broken cup to its original shape.

Or can we?

An international team of scientists led by the US Department of Energy (DOE) Argonne National Laboratory explored this problem in a first experiment and briefly returned the computer to the past. The results, published in the March 13 issue of the journal Science Report propose a new way to explore time-lapse in quantum systems. They also open up new possibilities for quantum computer program testing and error correction.

To achieve time reversal, the research team developed an algorithm for IBM public quantum computers that simulates the scattering of particles. In classic physics, this might look like a billiard ball that hits the ball and travels in a line. But in the quantum world, a scattering particle exhibits a broken mass that spreads in multiple directions. Reversing its quantum evolution is like twisting a ring that is created when a stone is thrown into a pond.

In nature, it is impossible to restore this particle to its original state – essentially reassembling broken teacups.

The main problem is that you need a "super system" or external force to manipulate the quantum waves at every point of the particle. However, the researchers point out that the timeline required for this supersystem to spontaneously and correctly manipulate quantum waves will be longer than the extension of the universe itself.

The team was not intimidated and began to determine how to overcome this complexity, at least in principle. Their algorithm simulates electron scattering through a two-stage quantum system, which is "quantized" by quantum computer qubits – the basic unit of quantum information – and its associated time evolution. The electron changes from a local or "see" state to a dispersed state. The algorithm then throws the process back and the particle returns to its original state – in other words, it moves back in time, if only for a fraction of the time.

Given that quantum mechanics is dominated by probabilities rather than determinism, the chances of achieving this time travel expertise are very good: the algorithm provides the same results 85% of the time in a dual qubit quantum computer.

"We have done things that were previously thought impossible," said Valerii Vinokur, senior scientist at Argonne who led the study.

The result deepens our understanding of the second law of thermodynamics – the system always moves from order to entropy rather than the opposite way – how it works in the quantum world. In the previous work, the researchers proved that by transmitting information, the second law can be partially violated in the quantum system. The quantum system is divided into remote parts and can be balanced with each other.

"The results also show that irreversibility is produced by measurements, which highlights the role of the concept of quantum physics," the co-author of the Moscow Institute of Research Gordey Lesovik said. Physics and technology.

This is the same concept as the Austrian physicist Erwin Schrödinger captured in his famous thought experiment, in which a cat sealed in a box may die and live until somehow Monitor its status. Researchers suspended these particles in this superimposed or quantum-constrained form by limiting their measurements.

"This is an important part of our algorithm," Vinokur said. “We measured the state of the system at the beginning and at the end, but did not interfere with the middle.”

This discovery may eventually lead to better error correction methods on quantum computers in which accumulated burrs generate heat and generate new heat. A quantum computer that can effectively jump back and clear errors can run more efficiently.

"At the moment, it's hard to imagine all the effects that this might bring," Vinokur said. "I am very optimistic, I believe it will be a lot."

The study also raises the question: Can researchers now find a way to make older people younger? “Maybe,” Vinokur joked, “There is the right amount of money.”

This work was done by an international team, including the Moscow Institute of Physical Sciences (Gordey Lesovik, Andrey Lebedev, Mikhail Suslov), the Federal Institute of Technology in Zurich (Andrey Lebedev) and the Argonne National Laboratory (Valerii Vinokur, Ivan Sadovskyy). Researcher. .

Funding for this study was provided by the US Department of Energy's Office of Science and Strategic Partnership Program (Swiss National Foundation and Theoretical Physics Promotion Foundation "BASIS").


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