A team of researchers from the Indian Institute of Technology Guwahati (IIT Guwahati) and the University of Stellenbosch have unravelled one of the most profound mysteries in physics — the quantum nature of gravity.

The study aims to understand how gravity behaves at incredibly small scales, like those of atoms and subatomic particles, where existing theories start to unravel.

This phenomenon can bridge two of the biggest pillars of modern science: general relativity and quantum mechanics.

Physics currently operates under two separate frameworks. Albert Einstein’s general relativity describes how gravity works for huge objects such as planets and stars, while quantum mechanics governs the behaviour of particles at the atomic and subatomic levels.

Although the theories excel in their fields, they disagree when it comes to understanding how gravity works at the quantum level. This created a substantial gap in our understanding, which researchers hope to address through the study of quantum gravity.

The study focuses on gravity-induced entanglement (GIE) and is being conducted under the direction of Dr Bibhas Ranjan Majhi, Associate Professor, Department of Physics at IIT Guwahati, and Dr Partha Nandi, University of Stellenbosch, South Africa. The findings have been published in the Physics Letters B journal.

According to a statement from the team, the new research takes a unique approach by studying how gravity may lead to entanglement, a phenomenon in quantum mechanics in which two particles become linked so that the state of one affects the other regardless of their distance.

Gravity-induced entanglement suggests that under certain situations, gravitational forces can create this quantum connection, revealing a quantum aspect of gravity.

Dr Majhi explained, “We have developed a theoretical framework that connects a two-dimensional quantum harmonic oscillator with gravitational waves—ripples in space-time caused by massive objects like black holes. This approach bypasses the limitations of classical communication methods and explores whether quantized gravitational waves can induce entanglement. Our findings show that while classical gravitational waves do not generate entanglement, the quantum version of these waves does, at the second order of gravitational perturbation.”

The study has far-reaching implications. If gravity-induced entanglement can be detected with gravitational wave detectors, it could be the first proof that gravity functions at the quantum level. This discovery could shed light on other cosmic mysteries, like the nature of dark matter and dark energy, two enigmatic components that make up the vast majority of the universe but remain poorly understood.

The research conducted by Dr Majhi and Dr Nandi is a major advancement in our understanding of the quantum nature of gravity. In addition to advancing the search for quantum gravity, their work also lays the foundation for further discoveries, potentially bringing together our understanding of the universe’s largest and smallest components.