Scientists in Wales have built the world’s most sensitive table-top interferometer, which is a miniature, ultra-precise instrument capable of measuring distortions in space-time smaller than a trillionth of a human hair.
The research team at Cardiff University took a bold step toward understanding the quantum nature of gravity by setting new limits on the existence of very high-frequency gravitational waves.
The experiment, also known as the Quantum Enhanced Space-Time measurement (QUEST), was developed at Cardiff University’s School of Physics and Astronomy.
According to the team, QUEST can measure changes in length 100 trillion times smaller than the width of a human hair. It set a new record for sensitivity in just a three-hour experiment. The results are expected to help scientists study new physics about space-time, gravity, and the existence of dark matter.
Unlocking quantum gravity
Gravitational waves, which are ripples in the fabric of space-time first predicted by Einstein, are typically detected at low frequencies by observatories like LIGO and Virgo, which listen for signals from events such as black hole collisions.
But waves at much higher frequencies, produced by phenomena like primordial black holes or processes in the early universe, have remained elusive.
To tackle the challenge, the team employed advanced interferometry, a technique that merges laser light reflections from mirrors to detect infinitesimal distance changes. They then used it to probe the faintest fluctuations in space-time.
“Our experiment is trying to answer the question of whether space-time is ‘quantized’,” Abhinav Patra, MSc, a doctoral student in the university’s Gravity Exploration Institute and lead author of the study, stated. “Modern physics treats space and time not as two separate things, but as a single physical entity.”
By correlating data from two independent interferometers, the team ruled out certain high-frequency gravitational waves that might be predicted by quantum theories of gravity.
This correlation method allowed them to isolate potential signals from random noise and effectively filter out local disturbances like seismic vibrations or thermal fluctuations.
Measuring the impossible
Hartmut Grote, PhD, a physics professor at the university and co-author of the study, stated that the results demonstrate just how powerful compact instruments can be in exploring the frontier between quantum mechanics and relativity.
“Quantum theories of gravity can manifest themselves as fluctuations in space-time, which interferometers excel at measuring,” he revealed. “QUEST is an interferometric approach to the problem of quantum gravity.”
According to Grote, the QUEST experiment took the team four years to design, install and commission.
“So, it employs all the lessons learned from the technological developments made for the interferometric detection of gravitational waves to study quantum gravity,” Grote concluded in a press release.
Now that the team has proven the setup’s sensitivity, the next phase will involve months-long observation runs to push the detection threshold even further.
These future tests could help uncover space-time fluctuations predicted by some quantum gravity models and shed light on the interplay between dark matter, vacuum energy, and gravitational fields.
The study has been published in the journal Physical Review Letters.
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