A £1.2 million grant from UK Research and Innovation (UKRI) is funding a collaboration between Oxford Earth Sciences and the University of Cambridge’s Cavendish Laboratory to pursue a dual challenge in detecting extraordinarily faint signals from both deep within the Earth and from distant reaches of space. The Sensing the Earth with a novel QUantum-classical INterferometer array (SEQUIN) project will focus on “free oscillations,” the low-frequency vibrations that linger after major earthquakes, alongside the subtle gravitational waves emitted by orbiting black holes, signals often obscured by terrestrial vibrations. “This project is about bringing the worlds of Earth sciences and quantum physics together,” said Dr. Tom Kettlety of Oxford Earth Sciences. Researchers aim to build a hybrid system where seismometers and quantum sensors work in tandem, achieving a precision neither instrument could attain alone and potentially revealing new insights into Earth’s interior and fundamental cosmic phenomena.
SEQUIN Project: Hybrid Quantum-Classical Interferometer Array for Sensing
This interdisciplinary undertaking seeks to overcome limitations in detecting both faint gravitational waves from space and subtle vibrations within the Earth, leveraging the strengths of both quantum and classical sensing technologies. Researchers are specifically targeting “free oscillations” of the Earth, the low-frequency vibrations that persist after major earthquakes, as these reveal information about the planet’s deep internal structure and are notoriously difficult to measure with conventional seismometers. The core innovation lies in a hybrid approach, combining the precision of quantum sensors with established seismological techniques; this synergy is expected to yield significantly improved detection capabilities.
Tom Kettlety explained the project’s ambition to merge traditional earthquake measurement with quantum gravity sensors. “We’re trying to combine the way we normally do things in seismology with sensors that use quantum physics to measure gravity very precisely. By building a sensing system where the seismometers help the quantum sensors and vice versa, we will develop methods to detect signals that are difficult to measure.” The project’s practical applications extend beyond fundamental physics, with anticipated benefits for monitoring geological carbon dioxide storage sites in the North Sea, a crucial component of climate change mitigation efforts.
Associate Professor Paula Koelemeijer highlighted the potential for new insights, stating, “The sensitivity of the atom interferometer at very long periods provides a new way of measuring some of the faintest signals in both physics and Earth sciences. This enables exploration of the most difficult to observe standing waves of the Earth, opening up new ways to study the deep Earth.” Professor Mike Kendall added, “This opens the door not only to improved gravitational wave detection, but also to a deeper understanding of the Earth’s internal processes,” emphasizing that “The system will achieve far greater precision than either instrument could alone.” The project also benefits from contributions from the United States Geological Survey (USGS), UKRI-STFC Boulby Underground Laboratory, the University of Glasgow, and the Université de Strasbourg, who will provide specialized instrumentation and expertise to enhance the sensing network.
Earth’s Free Oscillations & Gravitational Wave Detection Methods
Simultaneously, the project intends to capture long-lived gravitational waves emanating from orbiting black holes, a phase preceding collision that offers richer data than the cataclysmic event itself. This dual focus necessitates innovative approaches to filter out interfering signals, as both phenomena are incredibly faint and easily obscured by background noise. The core of SEQUIN’s strategy lies in a hybrid sensing system combining conventional seismometers with quantum sensors; this integration is designed to leverage the strengths of each technology, allowing them to mutually enhance signal detection.
This exciting project is all about bringing the worlds of Earth sciences and quantum physics together. We’re trying to combine the way we normally do things in seismology (i.e., measuring earthquakes) with state-of-the-art sensors that use quantum physics to measure gravity incredibly precisely. By building a sensing system where the seismometers help the quantum sensors and vice versa, we will develop methods to detect very difficult to measure signals, like the echoes of the deepest parts of the Earth, and potentially signs of fundamental phenomenon like gravitational waves and dark matter.
