Hexagonal boron nitride quantum sensors – ANR-NSF QISE

Overview

Sensors based on quantum phenomena have tremendous potential to improve the accuracy, sensitivity, and precision over well-established technologies. Crystalline hexagonal boron nitride (hBN) is an especially promising platform for advance quantum sensors due to its many advantageous properties: it is a two-dimensional van der Waals material with an ultrawide bandgap, its monolayers are chemically and thermally stable and they can be in direct contact to, or even embedded in, the system to be probed. In this project, color centers in hBN with optically detectable spin states created by boron vacancies and impurity doping will be optimized to measure magnetic and electric fields. High quality hBN crystals with quantified defect densities will be grown under the direction of J.H. Edgar at Kansas State University (KSU) from molten metal solutions. Guillaume Cassabois and Vincent Jacques at the Centre National de la Recherche Scientifique (CNRS) will thoroughly characterize their optical and quantum properties. A feedback loop will be established between institutions, in which KSU will grow hBN crystals with the defects that CNRS needs to address specific issues associated with the fabrication of quantum sensors, and CNRS will provide KSU with material characterization to evaluate and improve the crystal growth process. This project will address key questions for optimizing hBN quantum sensing including: (1) Which point defects, such as those created by boron vacancies and carbon doping, are most effective in quantum sensors? (2) What defect densities and defect configurations are needed to optimize device performance? (3) To what extent can quantum sensing be improved by employing hBN with specific boron and nitrogen isotopes? (4) Can the ultimate quantum sensing of magnetic and electrical fields be produced from hBN monolayers?

Intellectual Merit

This project presents a coordinated experimental investigation into methods of creating, and the properties of, optically detectable spin defects in hBN for quantum sensing of magnetic and electric fields. Free-standing, high quality hBN crystals will be grown by precipitation from molten metal solutions. The point defects to be studied include boron vacancies created by nuclear transmutation, carbon introduced during crystal growth, and ion implantation into hBN. This will enable control over the concentration of defects and their configurations. To gain a deep understanding of the fundamental properties of the defects and to optimize the quantum sensor sensitivities, hBN crystals with specific boron (10B and 11B), nitrogen (14N and 15N), and carbon dopants (12C and 13C) will be studied. Preliminary results suggest that h10B15N is the best for quantum sensing, due to the lower nuclear spin background of the 15N isotope. Defect energy states in the crystals will be established by deep ultraviolet photoluminescence (3 eV to 6.5 eV) and optically detected magnetic resonance (ODMR). Quantum devices will be fabricated, and their performance in detecting magnetic and electric fields tested.

Broader Impacts

This project will provide guidelines for producing hBN with the best properties for realizing quantum sensors. Such devices will offer improved sensing for health, security, commercial, industrial, and scientific applications. A priority of this project is to train the next generation workforce in quantum engineering. It will provide excellent learning opportunities about crystal growth, optical characterization of materials, and quantum properties and applications. This project will strengthen the established international collaboration between KSU and CNRS. Both the KSU and CNRS groups will be involved in the outreach activities that are designed for the public, young women, and students from underrepresented groups. These activities will demonstrate the creative aspects, the collaborative nature, and benefits quantum science and technology have on society.