Researchers at Purdue University have made significant strides by creating one-dimensional boron nitride nanotubes (BNNTs) that are currently pending a patent. These nanotubes incorporate spin qubits, or spin defects, and are considerably more adept at detecting off-axis magnetic fields at high resolutions compared to the conventional diamond tips typically utilized in scanning probe magnetic-field microscopes.
Tongcang Li, a physics and electrical and computer engineering professor, is at the forefront of this innovative work. He is also affiliated with the Purdue Quantum Science and Engineering Institute. The team working alongside him includes graduate students Xingyu Gao, Sumukh Vaidya, and Saakshi Dikshit, who are co-authors of a study published in the peer-reviewed journal Nature Communications.
“The sensitivity of BNNT spin qubits to off-axis magnetic fields surpasses that of a diamond nitrogen-vacancy center, which primarily responds to fields aligned with its axis but less so to perpendicular fields,” Li explained. “In addition, BNNTs are more cost-effective and have greater durability than fragile diamond tips.”
Possible applications for BNNTs include quantum-sensing technologies that assess variations in magnetic fields and gather data at the atomic level.
“They are also valuable in the semiconductor sector and for nanoscale MRI, or magnetic resonance imaging,” Gao added.
Li has shared insights about these nanotube spin qubits with the Purdue Innovates Office of Technology Commercialization, which has taken steps to file for patents to safeguard this intellectual property.
Testing and Advancements in BNNT Spin Qubits
The team has tested their system on specially constructed laboratory equipment that includes lasers, detectors, and signal generators for managing the quantum states of the nanotube spin qubits.
“These BNNT spin qubits are responsive to magnetic fields and feature optically detected magnetic resonance,” Vaidya noted. “When they interact with a magnetic field, the energy levels of the spin qubits within the BNNTs change, and this can be measured utilizing light.”
In initial tests, BNNTs demonstrated performance that was comparable to that of diamond tips.
“Given that the boron nitride nanotubes are much smaller in size than the diamond tips, we anticipate achieving better results for the system,” Dikshit mentioned.
Li indicated that the Purdue team is focused on enhancing the spatial resolution and magnetic field sensitivity of the BNNT spin qubit system. Such advancements could facilitate quantum sensing of phenomena at the atomic level.
“This would allow for exceptionally detailed scanning of surface magnetic characteristics,” Vaidya explained. “By boosting the sensitivity, we can either obtain more accurate information or achieve quicker readouts of external magnetic fields, both of which hold significance in quantum science, data storage, as well as medical and semiconductor applications.”
