Igor Pikovsky, a physicist at Stevens Institute of Technology, along with his team, is pioneering an innovative experiment aimed at capturing individual gravitons—particles previously believed to be nearly undetectable. This groundbreaking work signals a new era in quantum gravity research.
Expected detection of single graviton signatures from gravitational waves in future experiments. Image credit: I. Pikovski.
Modern physics faces a significant challenge. The two foundational pillars—quantum theory and Einstein’s general theory of relativity—appear contradictory at a glance.
While quantum theory depicts nature through discrete quantum particles and interactions, general relativity interprets gravity as the smooth curvature of space and time.
A true unification demands that gravity be quantum in nature, mediated by particles called gravitons.
For a long time, detecting even a single graviton was deemed nearly impossible.
Consequently, the problem of quantum gravity has mostly remained a theoretical concept, with no experimental framework for a unified theory in view.
In 2024, Dr. Pikovsky and his collaborators from Stevens Institute of Technology, Stockholm University, Okinawa Institute of Science and Technology, and Nordita demonstrated that *detecting gravitons* is indeed feasible.
“For ages, the idea of detecting gravitons seemed hopeless, which is why it wasn’t considered an experimental question,” Pikovsky stated.
“Our findings indicate that this conclusion is outdated, especially with today’s advanced quantum technologies.”
The breakthrough stems from a fresh perspective that combines two pivotal experimental innovations.
The first is the detection of gravitational waves—ripples in spacetime generated by collisions between black holes and neutron stars.
The second innovation is the advancement in quantum engineering. Over the last decade, physicists have mastered the cooling, control, and measurement of larger systems in true quantum states, leading to extraordinary quantum phenomena beyond the atomic scale.
In a landmark experiment in 2022, a team led by Yale University professor Jack Harris showcased the control and measurement of individual vibrational quanta of superfluid helium exceeding 1 nanogram in weight.
Dr. Pikovsky and his co-authors realized that by merging these two advancements, it becomes possible to absorb and detect a single graviton. A passing gravitational wave could, theoretically, transfer exactly one quantum of energy (or one graviton) into a sufficiently large quantum system.
The resulting energy shift may be minimal but manageable. The primary hurdle lies in the fact that gravitons seldom interact with matter.
Nevertheless, in quantum systems scaled to the kilogram level, it is feasible to absorb a single graviton in the presence of strong gravitational waves generated by black hole or neutron star mergers.
Thanks to this recent revelation, Dr. Pikovsky and Professor Harris are collaborating to construct the world’s first experiment specifically designed to detect individual gravitons.
With backing from the WM Keck Foundation, they are engineering centimeter-scale superfluid helium resonators, moving closer to the conditions needed to absorb single gravitons from astrophysical gravitational waves.
“We already possess essential tools; we can detect single quanta in macroscopic quantum systems; it’s merely a matter of scaling up,” Professor Harris elaborated.
The objective of this experiment is to immerse a gram-scale cylindrical resonator within a superfluid helium container, cool the setup to the quantum ground state, and utilize laser-based measurements to detect individual phonons (the vibrational quanta transformed from gravitons).
This detector builds upon an existing laboratory system while advancing into uncharted territory—scaling masses to the gram level while maintaining exceptional quantum sensitivity.
Successfully demonstrating this platform sets the stage for the next iteration, which will be optimized for the sensitivity required to achieve direct detection of gravitons, thus opening new experimental avenues in quantum gravity.
“Quantum physics began with controlled experiments involving light and matter,” Pikovsky noted.
“Our current aim is to bring gravity into this experimental domain and investigate gravitons much like physicists studied photons over a century ago.”
Source: www.sci.news
