Quantum diamond magnetic field sensors for improved situational awareness

Better situational awareness means control – and improved safety of personnel. Quantum sensors using deliberately flawed diamonds can render the ground transparent to enable visualising, tracking, and classifying of objects that are underground.

Developed by a team of academics at the University of Melbourne and RMIT University, working with industry and engineers from Phasor Innovation, quantum diamond magnetometers can sense the direction and strength of very weak magnetic fields.

The Quantum Diamond Magnetometry team are exploring ways to use these sensors in navigation, underground and undersea sensing, aerospace, the space domain, and healthcare.

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Diamond defects create delicate quantum sensors

At the forefront of the current quantum technology revolution is an ancient material: diamond.

Pure diamond is made from carbon atoms arranged in an orderly crystal lattice. Disrupting this lattice on the atomic scale by switching individual carbon atoms with nitrogen atoms transforms diamond from a coveted jewel into a delicate quantum sensor. Tiny changes in the environment, such as variations in magnetic fields, alter the quantum mechanical properties of the defect centres. The changes in the quantum mechanical properties are conveniently detected by changes in fluorescent light emitted by the defect centres.

“Diamond quantum sensors are unique in that they can operate at room temperature in ambient unshielded conditions and with sensitivities that surpass their classical counterparts,” says Associate Professor David Simpson, a University of Melbourne researcher in the School of Physics.

Superconducting quantum interference devices and optically pumped magnetometers are complementary quantum sensors for detecting magnetic fields. However, they are often constrained in terms of cost, size, dynamic range, and operating temperature. Diamond quantum sensors do not suffer from these limitations and can operate under extreme environmental conditions.

Another key advantage of diamond-based quantum sensors is that the magnetic field sensors do not drift over time. The defect centres are locked into the crystal lattice of the hardest known material. Researchers can also gain control over the location and orientation of the defects in the lattice. This allows for accurate and stable vector magnetic field sensing.

Australia’s first portable diamond magnetic field sensor

Magnetic field sensing is useful in applications ranging from Defence, geo-surveying and mineral exploration through to healthcare.

As part of the Army Quantum Technology Challenge, the Quantum Diamond Magnetometry team demonstrated Australia’s first portable quantum diamond magnetometer. The fibre-based magnetometer was designed to detect and track the movement of metallic objects underground and underwater.

The team is now funded by Army and Defence Science and Technology Group to design and build ultra-sensitive quantum vector magnetometers that can operate in complex urban environments.

“The goal here is to establish a platform technology that can solve a number of problems in Defence,” Associate Professor Simpson says.

Directional magnetic field sensors are emerging as an alternate solution for navigation, especially in environments where access to GPS is denied or not available. By detecting the direction and strength of Earth’s magnetic field, quantum diamond sensors can be used to create a ‘magnetic map’ to navigate by.

The sensitivity of the quantum sensors also allows researchers to detect far smaller electrical and magnetic fields, useful in health applications. The team hopes to translate the sensitive vector magnetometer technology into clinically relevant sensors for magnetic sensing of heart and brain signals. Our brains are made of masses of neural circuits. These are connected collections of neurons that work together to create functions like reflexes as signals pass through the circuit.

Detangling these circuits would help us understand how the brain functions and shed light on neurological diseases.

“If we can increase the sensitivity and further reduce the size of the diamond sensors, we hope to apply arrays of these sensors to map the magnetic signals of the brain in complex environments to understand how the brain functions, and is impacted by disease,” says Associate Professor Simpson.

Developed in deep partnership

This technology is the result of an extensive collaboration between academics from the University of Melbourne and RMIT University, and engineers from Phasor Innovation. The Quantum Diamond Magnetometry team has complementary expertise around device fabrication and construction, magnetic simulations and probing the fundamental properties of the diamond material.

“Our role here at the University of Melbourne is to engineer the next generation of diamond materials, and to design and construct Australia’s most sensitive diamond vector magnetometer,” says Associate Professor Simpson.

The RMIT University team are focusing on unlocking the mysteries of the quantum diamond material itself – benchmarking their performance against conventional materials.

“In addition, RMIT are researching the theoretical aspects of the nitrogen-vacancy defects within diamond and the optical collection of the fluorescence of the quantum sensing diamond chip,” says Professor Brant Gibson, a physicist from RMIT University.

RMIT University and the University of Melbourne have worked together on this technology for more than 15 years, with Phasor Innovation, an independent Australian-owned technology company, bringing their capabilities to the project in early 2020.

“Phasor Innovation are experts in electromagnetic and electronic engineering. We’re using all those skills to translate this technology into the real world,” says Phasor Innovation Technical Director Andy Sayers.

“We are excited to be working at the forefront of the quantum revolution. Collaborations between universities and agile companies like Phasor are the best way to fast-track innovative technology development for Defence,” he says.

The partners are now engaging with Defence prime industries to further develop applications of this technology.

Sovereign quantum diamond production

Further improvements to the performance and sensitivity of quantum diamond magnetometers are on the horizon. The quantum sensor currently uses the best commercially available diamond material. But the University of Melbourne, in partnership with five Australian universities, recently received funding from the Australian Research Council Linkage Infrastructure, Equipment and Facilities scheme to establish a national facility for the production of quantum-grade diamond materials. The unique fabrication facility will be commissioned in early 2023.

“It’s really important for Australia to have sovereign capability over the production of these quantum diamond materials, so we can go end-to-end from fundamental research through to a commercialised product,” Associate Professor Simpson says.

First published on 30 January 2023.

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