While quantum computing appears to be the important element among developing technologies based on the behavior of matter and energy at the atomic and subatomic level, another direction promises to open a new door for scientific research itself — quantum microscopy.
With advances in quantum technologies, new microscopic techniques are becoming possible — ones that can see electric currents, detect fluctuating magnetic fields, and even see individual molecules on a surface.
A prototype of such a microscope, showing high-resolution sensitivity, has been developed by an Australian research team led by Professor Igor Aharonovich of the University of Technology Sydney and Dr Jean-Philippe Tetienne of RMIT University. The team’s findings have now been published in Physics of Nature.
Quantum microscopy is based on atomic impurities, which after laser illumination emit light that can be directly related to interesting physical quantities such as magnetic field, electric field or the chemical environment near the defect.
Professor Aharonovich said the ingenuity of the new approach was that, unlike the bulky crystals often used for quantum sensing, the research team had used atomically thin layers, called hexagonal boron nitride (hBN).
“This van der Waals material — that is, composed of strongly connected two-dimensional layers — can be made very thin and conform to arbitrarily rough surfaces, thus enabling high-resolution sensitivity,” Professor Aharonovich said.
“These properties led us to the idea of using ‘quantum active’ hBN sheets to perform quantum microscopy, which is essentially an imaging technique that uses arrays of quantum sensors to create spatial maps of the quantities they are sensitive to,” said Dr Tetienne. .
“Until now, quantum microscopy has been limited in its spatial resolution and application flexibility due to the interface problems inherent in using a bulky 3D sensor. By using a van der Waals sensor instead, we hope to extend the utility of quantum microscopy to arenas which in the past were inaccessible”.
To test the prototype’s capabilities, the team performed quantum sensing on a technologically relevant magnetic material — a flake of CrTe2, a van der Waals ferromagnet with a critical temperature just above room temperature.
The hBN-based quantum microscope was able to image the magnetic regions of the ferromagnet, with nanoscale proximity to the sensor and under ambient conditions — something previously thought to be impossible.
Additionally, using the unique properties of hBN defects, a simultaneous temperature map was recorded, confirming that the microscope can be used to perform correlative imaging between the two quantities.
Main authors for the Physics of Nature PhD students Alex Healey (University of Melbourne) and Sam Scholten (University of Melbourne) and early career researcher Tieshan Yang (UTS), said the van der Waals nature of the sensor enabled dual sensing of magnetic properties and temperature.
“Because it’s so thin, not much heat can dissipate through it, and any temperature distribution that exists is the same as if the sensor wasn’t there,” they said. “What started as an experimental nuisance ended up being a hint toward a capability of our microscope that is unique among today’s alternatives.”
“There is enormous potential for this new generation of quantum microscopy,” said UTS senior researcher Dr Mehran Kianinia. “Not only can it operate at room temperature and provide simultaneous information on temperature, electric and magnetic fields, but it can be seamlessly integrated into nanoscale devices and withstand very harsh environments, as hBN is a very rigid material.
“Major future applications include high-resolution MRI (magnetic resonance imaging) and NMR (nuclear magnetic resonance) that can be used to study chemical reactions and trace molecular origins, as well as applications in space, defense and agriculture where remote sensing and the key illustration.”
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