Geological surveying using quantum sensors allows us to understand the subsurface of Earth with precision, accuracy and higher depth penetration as compared to traditional geological surveying techniques. This article discusses how quantum sensors can be employed in geological surveying, commercial examples, and recent relevant studies.
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Geological Surveying Techniques that use Quantum Sensors
Quantum sensing can be employed in geological surveying by several techniques and tools that utilize quantum sensors, such as quantum gravity gradiometers, magnetometers, and quantum resonance imaging.
Gravity gradiometry is a fundamental tool in geological surveying that provides information about subsurface density variations. Quantum gravity gradiometers operate by creating highly sensitive quantum interferometers using cold atoms or Bose-Einstein condensates, which enables measuring the tiny differences in gravitational force at different points, providing detailed information about the geological structures beneath the Earth's surface. This provides a more accurate and high-resolution gravity map, aiding in the identification of potential mineral deposits or geological faults.
Similarly, geological formations exhibit magnetic field variations, which are utilized as sensing mechanisms for geological surveying. Quantum sensors, such as magnetometers based on nitrogen-vacancy (NV) centers in diamond, operate by detecting the quantum properties of electrons within the diamond lattice, enabling geoscientists to map magnetic anomalies with high accuracy and identify subsurface structures and geological features.
Another technique is quantum resonance imaging, which involves utilizing quantum sensors to detect the interactions between subsurface materials and external electromagnetic fields, providing detailed images of the subsurface and revealing the distribution of different geological materials.
Recent Developments
Bayesian Inference in Tunnel Detection
A recent study introduces a practical quantum gravity gradient sensor designed to overcome limitations in gravity cartography caused by long measurement times and vibrational noise. The sensor achieves a statistical uncertainty of 20 E and demonstrates sub-meter spatial resolution in geological surveying.
The researchers successfully detected and located a 2-meter tunnel with high precision using Bayesian inference. The sensor's hourglass configuration, based on cold atom gravity gradiometry, effectively minimizes noise from various sources, allowing robust and compact operation in the field.
The study envisions applications in mapping aquifers, archaeology, soil property assessment, and infrastructure construction, providing an advanced tool for improved underground exploration. As per the study, future enhancements could further enhance sensitivity and reduce measurement times, making quantum gravity sensors increasingly practical for diverse applications within the next 5–10 years.
Borehole-Deployable Quantum Gravity Sensors
Another study focuses on deploying cold atom-based sensors down boreholes for improved gravity surveys. Quantum technology gravity sensors, utilizing atom interferometry, demonstrate the potential for increased survey speeds and reduced calibration needs.
The researchers successfully developed a borehole-deployable magneto-optical trap with a compact size, robustness, and environmental resilience suitable for borehole conditions. This system generated atom clouds at 1-meter intervals in a 50-meter deep borehole, simulating in-borehole gravity surveys. The breakthrough aims to address the drawbacks of traditional borehole gravity sensors, offering higher precision and overcoming challenges related to size, weight, power consumption, and environmental conditions.
Mineral Exploration using SQUIDs
Superconducting quantum interference devices (SQUIDs) were explored in a 2022 study, showcasing developments in airborne vector magnetometers with ultra-low noise and high dynamic range. The study introduced an airborne full tensor gradiometer instrument and a ground-based transient electromagnetic method using SQUID-based receivers.
Additionally, a novel airborne quantum sensor-based system for audio-frequency magnetotellurics (QAMT) was presented, demonstrating its capability to extract magnetic field vectors and transfer functions for passive electromagnetic methods. The research highlighted successful demonstrations and performance evaluations, emphasizing the potential of quantum magnetometers, including SQUIDs, in advancing geophysical exploration tools for mineral exploration and subsurface imaging.
Commercial Examples
Several companies are involved in developing and producing quantum sensors for commercial geological surveying applications.
SBQuantum
SBQuantum employs quantum sensors, specifically quantum magnetometers utilizing nitrogen vacancy diamonds, to conduct advanced geological surveys, enabling precise, localized magnetic modeling of the Earth. Their dashboard allows clients to explore and navigate based on hidden fluctuations in the Earth's magnetic field.
SBQuantum aims to revolutionize various industries, including mining, navigation for autonomous vehicles, defense, security, and even space exploration.
Nomad Atomics
Nomad Atomics' suite includes compact cold-atom gravimeters for optimized performance, highly accurate globe sensors with sensitivity and zero drift, and robust instruments tested under extreme conditions. These sensors provide high accuracy by exploiting the quantum properties of atoms, enabling advanced field applications in resource monitoring, exploration, and navigation without reliance on external systems.
Conclusion
The precision and sensitivity offered by quantum technologies enable geoscientists to obtain more accurate and detailed information about geological structures, mineral deposits, and environmental conditions.
Although quantum sensors have immense potential in geological surveying, challenges like the complexity of quantum technologies, the need for specialized expertise, and the development of robust field-deployable quantum sensors must be addressed for their widespread adoption.
However, as research and development in quantum sensing progress, the future of geological surveying with enhanced quantum sensor-based exploration techniques looks bright.
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References and Further Reading
Choi, C. Q. (2022). New Quantum Sensor Sees Beneath the Beneath. IEEE Spectrum. [Online] Available at: https://spectrum.ieee.org/quantum-sensors-gravity-birmingham
SBQUantum. https://sbquantum.com/
Nomad Atmoics. https://www.nomadatomics.com/
Stray, B., Lamb, A., Kaushik, A., Vovrosh, J., Rodgers, A., Winch, J., ... & Holynski, M. (2022). Quantum sensing for gravity cartography. Nature. https://doi.org/10.1038/s41586-021-04315-3
Vovrosh, J., Wilkinson, K., Hedges, S., McGovern, K., Hayati, F., Carson, C., ... & Holynski, M. (2023). Magneto-optical trapping in a near-suface borehole. Plos one. https://doi.org/10.1371/journal.pone.0288353
Stolz, R., Schiffler, M., Becken, M., Thiede, A., Schneider, M., Chubak, G., ... & Terblanche, O. (2022). SQUIDs for magnetic and electromagnetic methods in mineral exploration. Mineral Economics. https://doi.org/10.1007/s13563-022-00333-3
Pilkington, Ben. (2022, March 10). Gravity Sensors: Innovations and Applications. AZoSensors. Retrieved on February 11, 2024 from https://www.azosensors.com/article.aspx?ArticleID=2482
Abbasi, Ibtisam. (2023, August 07). Real-Time Environmental Monitoring With Quantum Sensors. AZoQuantum. Retrieved on February 11, 2024 from https://www.azoquantum.com/Article.aspx?ArticleID=444
Ali, Owais. (2023, September 21). A Closer Look at Quantum Sensing's Applications. AZoSensors. Retrieved on February 11, 2024 from https://www.azosensors.com/article.aspx?ArticleID=289
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