Researchers use gold film to enhance quantum sensing with qubits in a 2D material

A spin qubit on a 2D material covered with a gold film. Spin defects in hexagonal Boron Nitride exhibit a record-setting contrast when placed on a gold film microwave stripline. They also show an optically detected magnetic resonance as well as plasmonic enhancements of their photon emission. Credit: Zhujing Li and Tongcang Xu
Quantum sensing can be used to surpass modern sensing technologies by applying quantum mechanics in engineering and design. These optimized processes can overcome current limitations in processes such as studying biological samples or magnetic materials. Quantum is the next frontier of sensing technology.

Recent discoveries of spin defects, known as qubits, in 2D materials (hexagonalboron nitride), have boosted the field ultrathin quantum sensing. The scientists ran into a problem in their discovery, which has triggered a scientific race to solve the issue. Their low brightness and low contrast magnetic resonance signal limited their sensitivity. Nature Physics published an article entitled "quantum sensors go Flat" two weeks ago, on August 9, 2021. It highlighted the advantages and also highlighted current shortcomings of this exciting new method of sensing via qubits within 2D materials.

Purdue researchers took on the challenge of solving qubit signal weaknesses in their research to develop ultrathin, 2D quantum sensors. Today, September 2, 2021, their publication in Nano Letters is out. They have resolved some of the key issues and achieved much better results by experimentation.

What was the difference? Dr. Tongcang Li (Associate Professor of Physics and Astronomy) explains how the gold film was instrumental in this breakthrough.

Li says that a gold film was used to improve the brightness of spin qubits up to 17-fold in our research. The gold film supports surface plasmon, which can accelerate photon emission. This allows us to collect more photons, and thus more signals. We also improved the magnetic resonance signal contrast by 10 times by optimizing the microwave waveguide design. We were able to significantly increase the sensitivity of these spin defect for local temperature and pressure detection.

Tongcang Li and his Purdue University team have created ultrathin quantum sensors using 2D materials. Credit: Cheryl Pierce, Purdue University

This research was done entirely at Purdue University. It was also collaborative across many departments. The paper's twelve authors are all from Purdue University. They include Xingyu gao, Boyang Jiang and Andres E. Luccasahuanga Allecca, Kunhong Shen. Mohammad A. Sadi. Abhishek. Solanki. Peng Ju. Zhujing Xu. Pramey Upadhyaya. Sunil A. Bhave. Tongcang Li. Xingyu gao is a graduate student in Li's lab.

Li says that this paper is a collaboration between Prof. Sunil A. Bhave and Prof. Yong P. Chen as well as my research group. These results were possible because of the collaborative atmosphere at Purdue.

The experiment involved the application of a green laser to spin qubits embedded in 2D materials. Under the green laser illumination, the material will emit photons of different colors (red and near infrared). Photon emission rates depend on temperature, pressure, and magnetic field. These spin qubits' brightness will change with changes in magnetic field, temperature or pressure. They were therefore able to measure the magnetic field accurately with high sensitivity.

The group hopes to use the spin qubits in the future to study new materials. The group also hopes to improve the signal so that one spin qubit within a 2D material can be used for quantum sensing. This will allow for unprecedented sensitivity, resolution, and sensitivity.

Continue reading Researchers achieve coherent control of solid state spin qubits using unconventional coherent controls

More information: Xingyu Gao et. al., High-Contrast Plasmonic Enhanced Shallow Spin Defects In Hexagonal Boron Nitride For Quantum Sensing. Nano Letters (2021). Xingyu Go et. al., High-Contrast Plastic-Enhanced Shallow Spin Declines in Hexagonal Boron Nitride For Quantum Sensing. (2021). DOI: 10.1021/acs.nanolett.1c02495 J.-P. Tetienne, Quantum sensors go flat, Nature Physics (2021). DOI: 10.1038/s41567-021-01338-5 Journal information: Nano Letters , Nature Physics