The interplay between the theory of relativity and quantum theory remains an intriguing challenge in scientific research. While each theory effectively explains phenomena at different scales, reconciling them into a unified framework has proven elusive. This pursuit of a “quantum theory of gravity” stands as one of the foremost unsolved tasks in science. The complexity of the mathematical equations involved and the difficulty in conducting appropriate experiments have contributed to the ongoing quest.

At the TU Wien in Vienna, Austria, an innovative approach has emerged: the utilization of a “quantum simulator” to explore these fundamental questions. Rather than directly investigating quantum particles in curved spacetime, researchers construct a “model system” that offers analogies and insights into the desired system. Excitingly, the team has demonstrated the exceptional effectiveness of this quantum simulator.

The recent publication in the Proceedings of the National Academy of Sciences (PNAS) details the collaborative efforts of physicists from the University of Crete, Nanyang Technological University, and FU Berlin.

The concept behind the quantum simulator is deceptively simple: Many physical systems, despite their apparent dissimilarities, may obey the same underlying laws and equations at a profound level. By studying one system, valuable knowledge about another system can be gained, even if they involve different particles or exist on different scales.

Prof. Jörg Schmiedmayer from the Atomic Institute at TU Wien explains, “We select a quantum system that we can readily control and manipulate in experiments, such as ultracold atomic clouds governed by electromagnetic fields in our case.”

By carefully configuring these atomic clouds, their properties can be translated into another quantum system, facilitating an understanding of the target system through observations made on the model atomic cloud system. This analogy can be likened to grasping insights into pendulum oscillation by examining the oscillation of a mass attached to a metal spring. Although these are distinct physical systems, they can be mutually translated.

Mohammadamin Tajik from the Vienna Center for Quantum Science and Technology (VCQ) at TU Wien, the lead author of the study, highlights their achievement: “We have successfully generated effects that resemble the curvature of spacetime using this approach.”

In the realm of atomic clouds, the researchers explore the speed of sound, akin to the speed of light propagating along a “light cone” in a vacuum. When influenced by massive objects, such as the sun’s gravitational pull, these light cones curve, deviating from their typical straight paths. This phenomenon is referred to as the “gravitational lens effect.”

Remarkably, the team demonstrates that similar effects can be observed within atomic clouds. Instead of the speed of light, the speed of sound is examined. Tajik remarks, “Now we have a quantum system that exhibits the effects of spacetime curvature and gravitational lensing, allowing us to study the connection between relativity and quantum theory in an entirely new way.”

The experiments successfully depict the shape of light cones, lensing effects, reflections, and other phenomena as expected in relativistic cosmic systems. Beyond fundamental theoretical research, these findings have implications for solid-state physics and the search for novel materials, which encounter similar questions amenable to exploration through these experiments.

Moving forward, the researchers aim to refine their control over the atomic clouds, enabling the acquisition of more comprehensive data. This includes the ability to precisely modify particle interactions, facilitating the recreation of highly complex physical scenarios that even supercomputers struggle to calculate.

The quantum simulator emerges as a valuable new tool for quantum research, complementing theoretical calculations, computer simulations, and direct experiments. By scrutinizing atomic clouds, the research team anticipates the discovery of previously unknown phenomena occurring at cosmic, relativistic scales. Without exploring the intricacies of minute particles, these phenomena might have remained concealed.

The integration of the quantum simulator not only enhances our understanding of the relationship between relativity and quantum theory but also opens doors to uncovering novel insights into the fabric of our universe.

By Impact Lab