Lab exchange grant: studying single photon emitters in hBN using EPR

Posted on 30th May 2024 in News

Stephanie Fraser, currently a PhD student at the University of Cambridge, was awarded an M4QN laboratory exchange grant to visit the lab of Dr Alice Bowen at the University of Manchester. The visit took place in February 2024.

A researcher sits in a lab full of EPR equipment while an experiment runs.
Stephanie Fraser in Alice Bowen’s lab in February 2024, running the experiments.

The purpose of the visit

Stephanie says, “The purpose of this laboratory exchange was to study single photon emitters in hexagonal boron nitride (hBN), using electron paramagnetic resonance (EPR) techniques at the national EPR facility at the University of Manchester. Our group has recently identified a new spin qubit (coherent 2-level system) in hBN, operating at room temperature. A better understanding of the microscopic structure of these single photon emitters, enabled by EPR spectroscopy, would help us to engineer our qubit control protocols for improved performance. During the visit I performed CW X-band EPR experiments on a range of hBN samples, with varying defect concentrations. The experiments were performed under varying irradiation intensities, temperatures, and sample orientations to increase the probability of observing a ground state triplet resonance. Given the absence of this resonance in all the data collected, we have discovered that our samples have very low spin concentrations. This insight has prompted us to explore novel sample preparation techniques for future EPR studies. During the laboratory exchange I gained an understanding of the theory underlying the technique and developed practical expertise in running EPR experiments (frequency tuning procedure and sample preparation). I also learned how to analyse EPR data and model electron spin systems using EasySpin software, which will be invaluable for future work in my PhD.”

Benefits to the UK materials and quantum community

hBN is a promising new host system for a variety of ambient temperature quantum applications, such as quantum networks and quantum sensing. These measurements lay the groundwork for future EPR studies that will contribute towards efforts to elucidate the microscopic structure of this defect class. Follow-up experiments will hopefully enable us to determine the ground-state electronic structure, including the values and signs of hyperfine coupling to proximal nuclear spins, which will help develop our model of the spin Hamiltonian. The insights gained may lead to the utilisation of this platform to develop nuclear spin quantum registers for memory applications. These goals strongly align with the aims of the Solid State Defects Materials Interest Group at M4QN.

Visit outcomes

This project facilitated a new collaboration between the QOMS group (Cavendish Laboratory, Cambridge) and Dr Alice Bowen’s group – combining our respective expertise in quantum optics and magnetic resonance. Once we develop new sample preparation techniques for increased spin concentration, future visits to the National EPR facility will be planned.

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