- Scientists are doing an experiment to test whether gravity is quantum
- In quantum mechanics, which describes the behavior of atoms and molecules – things behave differently from everything we know: they can exist in a quantum superposition that exists in two places at the same time.
- Now, scientists are investigating a way to find out if gravity works this way, by levitating micro diamonds in a vacuum.
- If gravity is quantum, it can ‘answer’ diamonds – a fascinating phenomenon that strongly links two objects in ways that are impossible in everyday life
- This research will help advance the understanding of black holes, the Big Bangand the universe
Quantum Gravity Experiment
Scientists are conducting an experiment to test whether gravity is quantum – one of the most profound questions about our universe.
General relativity and quantum mechanics are the two most fundamental descriptions of nature that we have. General relativity explains gravity on large scales while quantum mechanics explains the behavior of atoms and molecules.
The Challenge of Integrating Theories
Perhaps the most important unsolved problem in fundamental physics is the correct way to combine these two theories – to determine whether gravity works at the quantum level. While theoretical work suggests many possibilities, experiments are needed to fully understand the nature of gravity.
Global Consortium’s Revolutionary Experiment
For a hundred years experiments on the quantum nature of gravity seemed out of reach, but now scientists based at the University of Warwick, UCL, Yale (USA), Northwestern (USA), and Groningen (Holland) will collaborate to investigate this conundrum. .
Their new idea is to levitate two microdiamonds in a vacuum and put each one into a quantum superposition that exists in two places at the same time. This counter-intuitive behavior is a fundamental part of quantum mechanics.
Professor Morley’s Insight into Experimentation
Each diamond can be considered 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 that points out that it’s really amazing how everyday objects (and pets!) can exist in a quantum superposition that exists in two places in one chance. We want to test the limits of this idea.
“Atoms and molecules have been successfully placed in such a superposition state, but we want to do this with much larger objects. Our diamonds are made up of a billion atoms or more. To test the quantum behavior in gravity, we look for an interaction between two diamonds due to gravity.
“If gravity is a quantum, then it can entangle two diamonds. Entanglement is a unique quantum effect in which two objects are linked more strongly than is possible in our everyday life. For example , if two coins can be linked then you will see that every time you flip them, they will both land in the same way although it is impossible to know in advance whether they will both be heads or the same tail.
Challenges and Implications
There are still many challenges in realizing this idea, which the team will investigate during the project. “For example, we have to eliminate all interactions between nanoparticles except gravity, which is very challenging because gravity is very weak,” said Dr. David Moore, of Yale University.
Professor Morley, who is the founding director of Warwick Quantum, a new interdisciplinary initiative for Quantum Technology research, added: “For me, the most important problem in physics today is to create an experiment that can test of the quantum nature of gravity.This new project is an acceleration of our exciting journey towards it.
Perspectives From Collaborating Scientists
Professor Sougato Bose, UCL, commented “It is difficult to overstate how important it is for physicists to have experiments that can properly examine the integration of quantum mechanics and general relativity. People working on theories of quantum gravity like string theory usually focuses on what happened at high energies, near black holes, and the Big Bang.
“In contrast, our work is in the low energy regime right here on Earth, but it will also provide important information about if gravity is quantum. Also, the experiment can be considered a verification of a generic prediction of any quantum theory of gravity at low energies.
Professor Anupam Mazumdar, University of Groningen, added “On the way to understand the quantum nature of gravity, we can test other aspects of fundamental physics such as exotic deviations from Newtonian gravity as short distances.”
“This is a challenging experiment, and this project is a pathfinder to address some important technical challenges to make these tests of the quantum aspect of gravity a reality”, says Andrew Geraci , Associate Professor of Physics, Northwestern University.
The project is called ‘MAST-QG: Macroscopic superpositions towards witnessing the quantum nature of gravity’.
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