Scientists from several universities are collaborating on an experiment called "MAST-QG" to determine whether gravity has quantum properties. The experiment involves levitating microdiamonds in a state of quantum superposition and aims to combine general relativity and quantum mechanics. Although the research is complex, it could fundamentally change our understanding of gravity and have broad implications for physics.
Scientists are developing an experiment to test whether gravity is quantum - one of the most profound questions in our universe. In quantum mechanics, which describes the behavior of atoms and molecules, objects behave unlike anything we know: they can be in a quantum superposition of two places at the same time. General relativity and quantum mechanics are our two most fundamental descriptions of nature. General relativity explains gravity on large scales, while quantum mechanics explains the behavior of atoms and molecules.
Now, scientists are working on a way to determine whether gravity behaves in this way by levitating tiny diamonds in a vacuum. If gravity is quantum, it could "entangle" diamonds - an interesting phenomenon that can tightly bind two objects together in a way that's unlikely to happen in everyday life.
This research will help people understand the mysteries of black holes, the Big Bang and the universe.
The challenge of a unified theory
Arguably the most important open question in fundamental physics is the right way to combine the two theories—determining whether gravity operates at the quantum level. While theoretical studies suggest many possibilities, experiments will be needed to fully understand the behavior of gravity.
For a hundred years, experiments on the quantum nature of gravity seemed out of reach, but now scientists from the University of Warwick, University of London, Los Angeles, Yale University (USA), Northwestern University (USA) and the University of Groningen (Netherlands) will join forces to investigate this puzzle.
Their new idea is to levitate two microdiamonds in a vacuum so that each diamond is in a quantum superposition of two locations at the same time. This counterintuitive behavior is a fundamental feature of quantum mechanics.
Each diamond can be thought of as a smaller version of Schrödinger's cat. Lead researcher Professor Gavin Morley from the Department of Physics at the University of Warwick explained: "Schrödinger's cat was a thought experiment which suggested that it would be very strange if everyday objects (and pets!) could be in a quantum superposition of two places at the same time, and we wanted to test the limits of this idea.
Atoms and molecules have successfully entered this superposition state, but we wanted to do it with larger objects. Our diamonds are made up of a billion atoms or more. To test the quantum nature of gravity, we will look for gravitational interactions between two such diamonds.
If gravity were quantum, it could entangle two diamonds. Entanglement is a unique quantum effect in which two things are more closely connected than in our everyday lives. For example, if two coins were able to become entangled, you might find that they would land the same way every time you flipped them, even though it was impossible to know in advance whether they would be heads or tails. "
Challenges and Impact
There are many challenges to realizing this idea, which the team will look into during the project. "For example, we need to eliminate all interactions between nanoparticles except gravity, which is so weak, so that's extremely challenging," said Dr. David Moore of Yale University.
Professor Morley, founding director of Warwick Quantum, a new interdisciplinary initiative in quantum technology research, added: "For me, the most important question in physics at the moment is to develop an experiment that can test the quantum properties of gravity. This new project will accelerate our progress towards this goal."
Professor Sujato-Bose from the University of London, Los Angeles, commented: "The significance of having experiments that can explore the correct combination of quantum mechanics and general relativity cannot be overstated for physicists. People who study quantum gravity theories such as string theory usually focus on high-energy, black holes what happened nearby and at the Big Bang. In contrast, our work was performed in a low-energy environment on Earth, but it will also provide valuable information about whether gravity is quantum gravity. In addition, this experiment can also be seen as validating the general predictions of any quantum gravity theory at low energies."
Anupam-Mazumdar, professor at the University of Groningen, added: "On the way to understanding the quantum nature of gravity, we may be able to test other aspects of fundamental physics, such as short-range singular deviations from Newtonian gravity."
"This is a challenging experiment, and this project is a pathfinder in solving some of the key technical challenges to make these tests of quantum aspects of gravity a reality," said Andrew Geraci, associate professor of physics at Northwestern University.
The project is called "MAST-QG: Witnessing the macroscopic superposition of the quantum nature of gravity."
Compiled source: ScitechDaily