Quantum Gravity Sensing Takes the Plunge Into Underground BoreholesAugust 28, 2020 by Luke James
The Gravity Delve Project aims to harness the potential of quantum gravity sensing by exploring the technology in harsh underground borehole environments.
Civil engineers are often faced with the challenge of scouting out underground locations to lay cable, pipe, or conduits to supply necessary utilities like electricity, water, gas, and telecommunication services.
While many technologies exist for underground sensing, such as ground-penetrating radar, scientists have only recently turned to quantum technology for a better idea of what's going on beneath the surface.
What are Quantum Gravity Sensors?
According to researchers at the University of Birmingham, a new method known as quantum gravity sensing works by applying a technique called atom interferometry. This technique uses cold atoms "as ideal test-masses to create a gravity sensor which can measure a gravity gradient rather than an absolute value." Researchers claim this method bypasses noise sources that may interfere with sensing.
A BBC article explains that quantum sensing uses lasers to cool rubidium atoms to slightly above zero (-273°C). These atoms are first shot upward in a vacuum and measured as gravity pulls them back down.
a) Depiction of the probability of identifying a two-level atom in its excited state vs. the duration of the laser pulse to excite the atom in its ground state. b) How an atom interferometer works as a gravity sensor. Image used courtesy of Nature
While quantum sensors are already used in the oil and gas sectors with much success, quantum cold-atom sensors—which are designed to operate on the surface—are expected to be better at detecting and monitoring objects beneath the ground.
To date, however, not much attention has been paid to the potential benefits of quantum gravity sensors deployed in boreholes.
Quantum Gravity Sensors for BoreHoles
The Gravity Delve Project (GDP) brings together academics from the UK Quantum Technology Hub Sensors and Timing (led by the University of Birmingham) and Nemein Ltd, a down-hole technology specialist, to explore quantum gravity sensors based on atom interferometry.
Nemein Ltd is currently developing equipment that can be deployed in boreholes for energy harvesting and environmental sensing. According to the company, this technology will enable the University of Birmingham’s quantum sensor, developed as part of the GDP, to be deployed into the harsh conditions of the downhole environment.
Gravity sensors have already been used in the oil and gas sectors with success. Image used courtesy of the University of Birmingham
Dr. Jamie Vovrosh, the University of Birmingham-based researcher who is also the technical lead for the project, said that the project provides an opportunity to use the “extraordinary performance” of quantum cold-atom sensors in new applications, potentially opening up “a pathway towards realizing future economic and societal benefits.”
The group's research is published in the journal Nature.
Minimizing the Environmental Impact from Hydrocarbon Extraction
Building on work already undertaken by the University of Birmingham in cold-atom gravity sensors, the project will investigate borehole applications such as carbon capture and storage (CCS) and hydrocarbon and geothermal reservoirs.
It will also investigate how a commercially-viable quantum device could replace or enhance current technology to optimize CCS reservoirs and minimize the impact that hydrocarbon extraction has on the environment.
Different applications for quantum sensing. Image used courtesy of ESA and Teledyne Imaging
The researchers also state that the project will enhance the transition from fossil fuels to renewable energy. As part of the project, a design will be developed for an innovative borehole quantum cold-atom sensor, which could lead to the first deep borehole quantum sensor that is both cost-effective and efficient.
Once developed, atom interferometer-based technologies are expected to be significantly smaller, lighter, and more power-efficient with improved sensitivity and faster measurement times.
Nemein’s technical director, Lawrence Till, comments, “Gravity Delve is not just a project which will optimize CCS and borehole energy extraction. It is very significant as a relatable project to show quantum technology can be deployed in some of the harshest environments in the real world and demonstrate tangible benefits to the environment.”