Researchers answer fundamental question of quantum physics

शोधकर्ताओं ने क्वांटम भौतिकी के मूलभूत प्रश्न का उत्तर दियाQ include the increase of the ferromagnetic correlation range as a function of time t starting from t as the ramp proceeds in the critical regime with the critical point located at t = . 0. Treatment length t∣ determining domain size in the Kibble-Zurek (KZ) mechanism<उप>gs is greater than the maximum speed of the relevant sound, c, in the system. Credit: science advance (2022). DOI: 10.1126/sciadv.abl6850″ width=”800″ height=”530″/>

Schematic illustration of the dynamics during the phase transition in a two-dimensional spin-1/2 model. In the initial paramagnetic state (bottom), the spins align with the direction of the transverse magnetic field. A measurement of the spin configuration at that position along the ordering direction would then yield a random pattern of spins typically pointing up (blue cone) or down (red cone). After a slow ramp to the quantum critical point, the system develops a quantum superposition of ferromagnetic domains, which, when measuring the spin configuration along the ordering direction, will generate a collapse, typically on a mosaic of such domains (top). On the front side, we include the growth of the ferromagnetic correlation series as a function of time t, starting at t = −τ.Why As the ramp proceeds in the critical regime with the critical point located at t = 0. In the Kibble–Zurek (KZ) mechanism the healing length that determines the size of the domain is set at t∣.The relevant sound in the GS system exceeds the maximum speed of C. Credit: science advance (2022). DOI: 10.1126/sciadv.abl6850

An international team of physicists, with the participation of the University of Augsburg, has for the first time confirmed an important theoretical prediction in quantum physics. The calculations for this are so complex that they have proved to be too demanding even for supercomputers so far. However, the researchers succeeded in simplifying them significantly by using methods from the field of machine learning. The study improves understanding of fundamentals of the quantum world. Has been published in the magazine. science advance,

Calculating the speed of a single billiard ball is relatively simple. However, predicting the trajectory of a multitude of gas particles in a vessel that is constantly colliding, slowing down and deflecting is more difficult. But what if it is not clear at all how fast each particle is moving, so that at any given time they have infinitely many possible velocities, the only difference being their probability?

The situation is similar in the quantum world: quantum mechanical particles can also have all the possible properties at once. This makes the state of quantum mechanical systems very large. If you want to simulate how quantum particles interact with each other, you have to consider their complete state spaces.

“And it’s extremely complex,” said Prof. of the Institute of Physics at the University of Augsburg. Dr. Marcus Heyl says. “The computational effort grows exponentially with the number of particles. With more than 40 particles, it is already so large that even the fastest supercomputers are unable to cope. This is one of the biggest challenges.” quantum physics,

Neural networks make the problem manageable

To simplify this problem, Heyl’s group used methods from the field of machine learning—artificial Nervous system, With these, the quantum mechanical state can be improved. “It makes it manageable for the computer,” Heyl explains.

Using this method, scientists have investigated an important theoretical prediction that so far remains an outstanding challenge – the quantum Kibble–Zurek mechanism. It describes the dynamic behavior of physical systems called a . is called quantum phase transition, An example of a phase transition from a macroscopic and more spontaneous world is the transition from water to ice. Another example is the demagnetization of magnets at high temperatures.

If you go to the other side and cool the material, the magnet starts forming again below a certain critical temperature. However, this does not occur evenly across the material. Instead, many small magnets with differently aligned north and south poles are created at the same time. Thus, the resulting magnet is actually a mosaic of many different, smaller magnets. Physicists also say that it has flaws.

The Kibble–Zurek mechanism predicts how many of these defects can be expected (in other words, how many mini-magnets the material will eventually be made of). What is particularly interesting is that the number of these defects is universal and thus independent of microscopic details. Accordingly, many different materials behave exactly the same, even though their microscopic structure is completely different.

The Kibble-Zurek Mechanism and the Formation of Galaxies After the Big Bang

The Kibble–Zurek mechanism was originally introduced to explain the formation of structure in the universe. After the Big Bang, the universe was initially completely homogeneous, meaning that the hosted matter was completely uniformly distributed. It has long been unclear how galaxies, the Sun, or planets could form from such a homogeneous state.

In this context the Kibble–Zurek mechanism provides an explanation. As the universe was cooling, the faults developed like magnets. Meanwhile, these processes are well understood in the macroscopic world. But there is one type of phase transition for which it has not yet been possible to verify the validity of the mechanism – namely the quantum phase transition already mentioned. “They only exist at the absolute zero temperature point of -273 °C,” explains Heil. “So the phase transition doesn’t happen during cooling, but through a change in the interaction energy—you might think, perhaps, of varying the pressure.”

Scientists have now simulated such a quantum phase transition on a supercomputer. They were able to show for the first time that the Kibble–Zurek mechanism also applies in the quantum world. “It was by no means a clear conclusion,” says the Augsburg physicist. “Our study allows us to better describe the dynamics of quantum mechanical system of many particles and therefore to understand more precisely the laws that govern this alien world.”


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more information:
Markus Schmidt et al, Quantum phase transition dynamics in a two-dimensional transverse-field Ising model, science advance (2022). DOI: 10.1126/sciadv.abl6850

Provided by Universität Augsburg

Citation: Researchers answer the Fundamental Question of Quantum Physics (2022, September 22), retrieved 22 September 2022 from https://phys.org/news/2022-09-fundamental-quantum-physics.html.

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