A new scientific paper suggests using the interference of gravity waves to measure quantum gravity. Interference is a quantum phenomenon where the combination of two or more electromagnetic waves form a resultant wave, the sum of the original waves (i.e., bigger or smaller).
In the experiment, laser light is shone on an electron. If the electron absorbs the photon's energy, then the electron's spin changes either up or down. During quantum superposition, the electron spin is both up and down. Choosing an electron that is part of a large body, such as a diamond, the entire object—with a vast mass for quantum phenomena—would be in quantum superposition.
By applying a magnetic field, it is possible to separate the two quantum states. When these quantum states are brought together again by turning off the magnetic field, they create an interference pattern. "The nature of this interference depends on the distance the two separate quantum states have traveled. And this can be used to measure gravity waves." These waves are space contractions so that their passing affects the distance between the two separated states and, thus, the interference pattern. The hope is that entanglement between two large objects could be used to determine whether gravity is a quantum phenomenon.
Entanglement is a quantum phenomenon. When two objects interacting only through gravity show entanglement, gravity is also a quantum phenomenon. The experiment is a long shot with our current technology. Read more on the journal website.
Reference:
Ryan J Marshman et al., Mesoscopic interference for metric and curvature & gravitational wave detection, New Journal of Physics (2020). DOI: 10.1088/1367-2630/ab9f6c
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