(Phys.org) A group of theoretical physicists have proposed a ‘table-top’ device that could measure gravity waves and answer one of the biggest questions in physics: is gravity a quantum phenomenon? Quantum gravity has been the ‘missing link’ in physics for nearly a century.
The group includes Ryan J. Marshman, Peter F. Barker and Sougato Bose (University College London, UK), Gavin W. Morley (University of Warwick, UK) and Anupam Mazumdar and Steven Hoekstra (University of Groningen, the Netherlands) Their research is hailed as a new method to measure gravity waves. Instead of the current kilometers-sized LIGO and VIRGO detectors, the physicists working in the UK and in the Netherlands proposed a table-top detector. This device would be sensitive to lower frequencies than the current detectors and it would be easy to point them to specific parts of the sky
The key part of the device is a tiny diamond, just a few nanometres in size. “In this diamond, one of the carbons is replaced by a nitrogen atom,” explains assistant professor Anupam Mazumdar. This atom introduces a free space in the valence band, which can be filled with an extra electron. Quantum theory says that when the electron is irradiated with laser light, it can either absorb or not absorb the photon energy. Absorbing the energy would alter the electron’s spin, a magnetic moment that can be either up or down.
“We have a diamond that has up spin and down spin at the same time,” explains Mazumdar. 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 will 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 contractions of space, so that their passing affects the distance between the two separated states and thus the interference pattern.

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