The year 2019 was filled with hope for development of ultrathin quantum sensors as new studies at the time indicated that it was possible to harness spin defects known as qubits were in 2D materials to develop such sensors.
However, later the development came to a halt with new issues cropping up related to the sensitivity of spin qubits in hexagonal boron nitride. Scientists observed at the time that the sensitivity of the spin qubits was limited by their low brightness and the low contrast of their magnetic resonance signal.
A new article published in Nature Physics titled “Quantum sensors go flat,” highlighting the benefits and outlining current shortfalls of this new means of sensing via qubits in 2D materials.
A team of researchers at Purdue University took on the challenge of overcoming qubit signal shortcomings in their work to develop ultrathin quantum sensors with 2D materials. Their publication in Nano Letters demonstrates that they have solved some of the critical issues and yielded better results through experimentation.
Scientists used gold film to increase the brightness of spin qubits by up to 17-fold. Scientists added that the gold film supports the surface plasmon that can speed up photon emission so we can collect more photons and, hence, more signals. In addition, they improved the contrast of their magnetic resonance signal by a factor of 10 by optimizing the design of a microwave waveguide. As a result there has been a substantial improvement in the sensitivity of these spin defects for detecting magnetic field, local temperature and local pressure thereby removing quite a few hurdles in development of ultrathin quantum sensors.
In this experiment, the group applied a green laser and a microwave onto these spin qubits in a 2D material. The material will then emit photons with different colors (red and near-infrared) under the illumination of a green laser. The rate of photon emission depends on the magnetic field, temperature, and pressure. Therefore, the brightness of these spin qubits will change when the magnetic field, temperature, or pressure changes. Thus, they were able to accurately measure the magnetic field with high sensitivity.