The hypothesis of relativity functions admirably when you need to make sense of infinite-scale peculiarities —for example, the gravitational waves made when dark openings impact. Particle-scale phenomena like the behavior of individual electrons in an atom are well described by quantum theory. However, the two have not yet been combined in a way that is completely satisfactory. The search for a “quantum theory of gravity” is regarded as one of the most important scientific mysteries that remains unsolved.

This is part of the way, on the grounds that the arithmetic in this field is profoundly confounded. Simultaneously, performing appropriate experiments is intense. It would be necessary to create circumstances in which both quantum effects and relativity theory phenomena become apparent, such as light’s dual particle and wave nature and a spacetime curvature caused by heavy masses.

A new strategy has been developed specifically for this purpose at the TU Wien in Vienna, Austria: To answer such inquiries, a device known as a “quantum simulator” is utilized. A “model system” is created from which analogies can be used to learn more about the system of interest, which is quantum particles in curved spacetime, rather than directly investigating it. The researchers have now demonstrated how well this quantum simulator works.

Prof. Jörg Schmiedmayer of the Atomic Institute at TU Wien.

“We use a quantum system that we are confident we can manipulate and fine-tune in experiments. In our situation, an atom chip with electromagnetic fields is holding and controlling extremely cold atomic clouds.”

The journal Proceedings of the National Academy of Sciences (PNAS) has now published the results of this international collaboration between physicists from the University of Crete, Nanyang Technological University, and FU Berlin.

**Learning from one system about another **

The quantum simulator’s fundamental concept is straightforward: Numerous physical systems are comparable. It’s possible that these systems follow the same equations and laws at a deeper level, despite the fact that they are completely distinct types of physical systems or particles at different scales that appear to have little in common. This implies that one can learn something about a specific framework by considering another.

According to Prof. Jörg Schmiedmayer of the Atomic Institute at the TU Wien, “We take a quantum system that we know we can control and adjust very well in experiments.” An atom chip with electromagnetic fields holds and manipulates these ultracold atomic clouds in our case.”

Suppose you make the necessary adjustments to these atomic clouds so that their characteristics can be transferred to a different quantum system. In that case, the measurement of the atomic cloud model system can tell you something about the other system, similar to how a pendulum can tell you something about the oscillation of a mass attached to a metal spring. Despite the fact that they are two distinct physical systems, one can be transformed into the other.

**The gravitational lensing effect **

“We have now been able to show that we can produce effects in this way that can be used to resemble the curvature of spacetime,” states Mohammadamin Tajik, who is the first author of the current paper and works at the Vienna Center for Quantum Science and Technology (VCQ)—TU Wien.

Light travels in the vacuum along a so-called “light cone.” The speed of light is consistent; it travels the same distance in each direction at equal times. These light cones, on the other hand, are bent when the light is influenced by heavy masses like the sun’s gravitation. In curved spacetimes, the paths of light are no longer perfectly straight. “Gravitational lens effect” refers to this.

Atomic clouds now demonstrate the same. One examines the speed of sound rather than the speed of light. Presently, we have a framework wherein there is an impact that compares to spacetime ebb and flow or gravitational lensing, and yet, it is a quantum framework that you can depict with quantum field speculations,” says Mohammadamin Tajik. “With this, we have a totally new instrument to concentrate on the association between relativity and quantum theory.”

The experiments demonstrate that the shape of light cones, lensing effects, reflections, and other phenomena can be demonstrated in these atomic clouds precisely as anticipated in relativistic cosmic systems—a model system for quantum gravity. This isn’t just fascinating for creating new information for fundamental hypothetical examination — strong state physical science and the quest for new materials likewise experience questions that have a comparable design and can consequently be answered by such investigations.

“To find even more extensive data, we now want to better control these atomic clouds. Jörg Schmiedmayer provides an explanation: “For instance, interactions between the particles can still be altered in a very targeted manner.” The quantum simulator is able to re-create physical situations in this manner that are so difficult to calculate even with supercomputers.

As a result, in addition to theoretical calculations, computer simulations, and direct experiments, the quantum simulator emerges as a brand-new and additional source of information for the study of quantum phenomena. While concentrating on the nuclear mists, the exploration group desires to run over new peculiarities that might have been completely obscure up to now, which likewise happen on an infinite, relativistic scale — yet without a gander at minuscule particles, they may very well never have been found.

**More information:** Mohammadamin Tajik et al, Experimental observation of curved light-cones in a quantum field simulator, *Proceedings of the National Academy of Sciences* (2023). DOI: 10.1073/pnas.2301287120