Scientists are developing an experiment to test whether gravity is quantum – one of the deepest questions about our universe.
General relativity and quantum mechanics are the two most fundamental descriptions of nature we have. General relativity explains gravity on large scales while quantum mechanics explains the behaviour of atoms and molecules.
Arguably the most important unsolved problem in fundamental physics is the correct way to bring these two theories together – to determine whether gravity operates on a quantum level. While theoretical work has proposed many possibilities, experiments are 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 based at the Universities of Warwick, UCL, Yale (USA), Northwestern (USA), and Groningen (Holland) will work together to investigate this conundrum.
Their new idea is to levitate two microdiamonds in vacuum and put each into a quantum superposition of being in two places 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. Principal Investigator Professor Gavin Morley, Department of Physics, University of Warwick, explains: “Schrödinger’s cat is a thought experiment pointing out that it would be really weird if everyday objects (and pets!) could be in a quantum superposition of being in two places at once. We want to test the limits of this idea.
“Atoms and molecules have been successfully put into such a superposition state, but we want to do this with much larger objects. Our diamonds are made up of one billion atoms or more. To test the quantum nature of gravity, we would look for interactions between two such diamonds due to gravity.
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