The theory of relativity can be used to explain cosmic-scale events such as gravitational waves that occur when black holes collide. Quantum theory works well for describing particle-scale phenomena, such as the movement of individual electrons in an atom. However, it has not yet been possible to combine the two completely satisfactorily. The search for a "quantum theory of gravity" is one of the important problems science still hasn't solved.

This is because this field is quite complex mathematically. It is also difficult to conduct appropriate experiments. Because it is necessary to create situations where both the phenomena of the theory of relativity (for example, space-time bent by heavy masses) and quantum effects (for example, the dual nature of light in which it has particle and wave properties) are important.

## CURVED SPACE-TIME IN QUANTUM SIMULATOR

A new method was developed for this purpose at TU Wien in Vienna, Austria. A "quantum simulator" is used to form the basis of such questions. Instead of directly investigating the related system, namely the quantum particles in curved space-time, a "model system" is created and information about the related system can be obtained through analogy. Researchers have now shown that this quantum simulator works perfectly. University of Crete, Nanyang University of Technology and

Physicists from FU Berlin have published the results of this international collaboration in the Proceedings of the US National Academy of Sciences (PNAS).

## Getting information from one system about another system

The basic principle of the quantum simulator is clear: Many physical systems are similar to each other. At a deeper level, these systems may obey the same laws and equations. This could be completely different kinds of particles, or physical systems of different scales that at first glance have little to do with each other. Thus, it is ensured that one can learn about another system by examining another system.

Professor of Atomic Institute at TU Wien. "We take a quantum system in experiments that we know we can control and tune very well," said Jörg Schmiedmayer. says. "In our case, these are ultracold atomic clouds that are held and manipulated by an atomic chip with electromagnetic fields." he adds. Suppose these atomic clouds are correctly tuned so that their properties can be translated into another quantum system. In this case, information about another system can be obtained from the measurement of one atomic cloud model system. For example, information about the oscillation of a pendulum from the oscillation of a mass attached to a metal spring: These two systems are separate. One of the physical systems can be transformed into another.

## gravitational lens effect

“We have now been able to demonstrate that we can generate effects that can be used to simulate the curvature of space-time in this way,” said Mohammadamin Tajik from the Vienna Center for Quantum Science and Technology (VCQ) – TU Wien. says. Light propagates in space along the so-called "cone of light". It is equal to the speed of light. That is, light travels the same distance in all directions in equal time intervals. But these cones of light bend when light is affected by heavy masses, such as the sun's gravity. Light paths in curved space-times are not exactly straight. This is called the "gravity lens effect".

Atomic clouds can now show the same thing. Instead of the speed of light, the speed of sound is studied. “We now have a system where there is an effect that corresponds to space-time curvature or gravitational lensing,” said Mohammadamin Tajik. But there is also a quantum system that you can describe with quantum field theories.” says. "With this, we have an entirely new tool for studying the connection between relativity and quantum theory."

## A model system for quantum gravity

Experiments have shown that the shape of light cones, lensing effects, reflections, and other phenomena can be represented in atomic clouds exactly as would be expected in relativistic cosmic systems. It is not only of interest to generate new data for basic theoretical research. At the same time, solid-state physics and the search for new materials face questions of similar nature and can produce solutions through such experiments.

Jorg Schmiedmayer. “We want to control these atomic clouds to identify broader data. Interactions between particles can still be manipulated in a very targeted way.” she says. In this way, the quantum simulator can reconstruct physical states that are too complex for even supercomputers to compute.

Thus, the quantum simulator; it becomes a new source of information for quantum research such as direct experiments, theoretical calculations and computer simulations. In studying atomic clouds, the research team hopes to encounter new phenomena, hitherto completely unknown, but also occurring on a cosmic scale. These phenomena may never have been discovered without the help of tiny particles.

Source: Bridging Quantum Theory and Relativity: Curved Spacetime in a Quantum Simulator (scitechdaily.com)

Compiled by: Esra Tasci

Günceleme: 21/05/2023 23:01