Quantum computing could be the most exciting of the emerging technologies based on how matter and energy behave at the atomic and subatomic scales, but quantum microscopy also holds the potential to revolutionize scientific investigation.
New microscopy modalities that can observe electric currents, detect changing magnetic fields, and even view single molecules on a surface are now possible due to the development of quantum technology.
The University of Technology Sydney’s Professor Igor Aharonovich and RMIT University’s Dr. Jean-Philippe Tetienne have led an Australian research team that has created a prototype of this type of microscope that exhibits high-resolution sensitivity. The results of the group’s research have now been released in Nature Physics.
The quantum microscope relies on atomic imperfections that, after being illuminated by a laser, emit light that can be directly linked to important physical characteristics like the magnetic field, electric field, or the chemical environment around the defect.
Professor Aharonovich praised the study team’s innovative use of atomically thin layers known as hexagonal boron nitride (hBN) instead of the bulkier crystals frequently used for quantum sensing.
This van der Waals material—that is, made up of strongly bonded two-dimensional layers—can be very thin and conform to arbitrarily rough surfaces, thus enabling high-resolution sensitivity.
Igor Aharonovich, Professor, University of Technology Sydney
Dr. Jean-Philippe Tetienne added, “These properties led us to the idea of using ‘quantum-active’ hBN foils to perform quantum microscopy, which essentially is an imaging technique that utilizes arrays of quantum sensors to create spatial maps of the quantities they are sensitive to.”
“Until now, quantum microscopy has been limited in its spatial resolution and flexibility of application by the interfacing issues inherent in using a bulky three-dimensional sensor. By instead utilizing a van der Waals sensor, we hope to extend the utility of quantum microscopy into arenas that were previously inaccessible,” stated Dr. Tetienne.
To evaluate the prototype's performance, the team used quantum sensing on a flake of CrTe2, a van der Waals ferromagnet with a critical temperature of a few degrees above room temperature.
It was previously thought to be unachievable, yet the hBN-based quantum microscope could image the magnetic domains of the ferromagnet under ambient settings and with nanoscale proximity to the sensor.
Furthermore, a simultaneous temperature map was captured using the unique qualities of the hBN defects, demonstrating that the microscope can carry out correlative imaging between the two quantities.
The van der Waals nature of the sensor, according to the study’s lead authors, PhD students Alex Healey and Sam Scholten from the University of Melbourne and early-career researcher Tieshan Yang from UTS, allows for the dual detection of magnetic properties and temperature.
They stated, “Because it is very thin, not much heat is able to dissipate through it, and any temperature distribution that exists is the same as if the sensor were not there. What began as an experimental annoyance ended up being a hint towards a capability of our microscope that is unique among current alternatives.”
There is a huge potential for this new generation of quantum microscopy. Not only can it operate at room temperature and provide simultaneous information on temperature, electric, and magnetic fields, it can be seamlessly integrated into nanoscale devices and withstand very harsh environments, as hBN is a very rigid material.
Dr. Mehran Kianinia, Senior Researcher, University of Technology Sydney
“The main future applications include high-resolution MRI (magnetic resonance imaging) and NMR (nuclear magnetic resonance) that can be used to study chemical reactions and identify molecular origins, as well as applications in space, defense, and agriculture where remote sensing and imaging are key,” Dr. Kianinia added.
Healey, A. J., et al. (2022) Quantum microscopy with van der Waals heterostructures. Nature Physics. doi:10.1038/s41567-022-01815-5.