November 14, 2024 by Bob Yirka , Phys.org
Collected at: https://phys.org/news/2024-11-gravity-quantum-entity.html
A multi-institutional team of physicists is proposing an experiment to test whether gravity behaves as a quantum entity when measured. They published a description of their experiment in the journal Physical Review Letters and state that once a means for conducting the experiment has been achieved, they hope the results will lead to the development of a grand unified theory of physics.
Physicists have learned a lot about the makeup of the universe over the past century and have developed many theories to explain how everything works. Two of the biggest are Einstein’s theory of general relativity, which describes the visible or classical world, and quantum theory, which describes the quantum world.
But one thing physicists do not understand completely is gravity. They also do not know if it fits into general relativity or quantum physics. Figuring out what gravity is would go a long way toward the development of a grand unified theory of physics, which would tie the two fields together—one of the biggest goals in the physics world.
In this new research, the team has developed an idea for a so-called table-top experiment that could be used to show whether gravity is changed when measured—if so, that would give strong evidence that it is a quantum property.
The proposed experiment, in its simplest form, involves using one small diamond crystal as a device to measure the gravitational pull of another equally tiny diamond crystal—this one in a superposition state. Once it has been verified that the gravity of the second crystal is “felt” by the first crystal, the researchers would then measure the first crystal again to see if its final state was different than its initial state. If so, that would prove that gravity was changed due to being measured during the experiment, and thus, it must be a quantum property.
The researchers are hopeful that advances in technology will allow for such an experiment to be carried out—the crystals would have to weigh approximately 1 million times less than a grain of sand—in the near future, offering the possibility of proving that gravity is a quantum property.
More information: Farhan Hanif et al, Testing Whether Gravity Acts as a Quantum Entity When Measured, Physical Review Letters (2024). DOI: 10.1103/PhysRevLett.133.180201
Journal information: Physical Review Letters
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