Researchers are fine-tuning Nanoscale Quantum Sensors to desired targets The sensor enables advanced magnetic imaging with applications in superconductors and electronic devices.
Sensors surround us in our daily lives, from parking lights to smoke detectors and even atoms. Quantum sensors detect their surroundings using the properties of atoms.
For example, an atom changes its spin, which takes two values like magnetic poles, in response to a magnetic field.
Magnetic sensors have many applications in biomedical devices and research in quantum materials, including superconductors.
Kento Sasaki, an assistant professor at the University of Tokyo, says: “With such a new sensor, we want to see something unusual in the world that no one has seen before.”
The researchers wanted to create stable quantum sensors placed near targets such as wires and disks. But until now, it has been difficult to arrange atoms well enough to be able to detect minute variations in the magnetic field.
“Although individual quantum sensors are small, their potential is limited by the distance between the sensor and the monitor,” says Sasaki.
To solve the problem, the researchers developed a method for fabricating nanometer-sized quantum sensors on measuring targets.
As a quantum sensor, the group used boron vacancies or lattice defects on two sides of hexagonal boron nitride, a crystalline material containing nitrogen and boron atoms.
Functional boron space has become the new kid on the block since it was discovered as a quantum spin sensor in 2020.
The team obtained a thin film of hexagonal boron nitride by removing the tape from the crystal. The researchers attached the thin film to the target gold wire.
Then they bombarded the film with a high-speed helium ion beam, knocking out boron atoms and creating 100 nm2 boron holes. Each dot has many atomic-sized holes that make up tiny magnetic needles.
The closer the areas are to each other, the better the spatial resolution of the sensor. As the current flows through the wire, the team measured the magnetic field at each location based on the intensity of the light coming from the point in front of the microwaves.
The researchers were surprised when the measured values of the magnetic field coincided with the simulated values, indicating the effectiveness of the high-performance quantum sensor.
The change of the rotation position of the sensor in the presence of the magnetic field can be found even at room temperature, thus allowing easy detection of the magnetic field in the water area.
In addition, boron nitride nanofilms attach to materials only through van der Waals forces, which means that the quantum sensor easily adheres to various materials.
Image of the magnetic field created by the current flowing through the gold wire. This is the result of analyzing the magnetic field data for each defect. The good agreement of experimental results and simulation results shows the principle of quantum sensor nanoarray.
Sasaki and his team plan to apply this technique to research in condensed matter physics and quantum materials.
“It will allow to find the magnetic field directly from, for example, the special states at the edges of graphene and microscopic quantum dots,” adds Sasaki.
Quantum sensors the size of atoms are beginning to change the way we understand microscopic environments and therefore also understand macroscopic properties.
Their applications have passed basic scientific research. They can help in modeling the human brain, accurately geolocating, mapping underground environments, and detecting tectonic changes and volcanoes.
Sasaki and his team await their opportunities for nanoscale quantum sensors in semiconductors, magnetic materials, and superconductors.
Source: University of Tokyo
