The next higher matter in the quantum realm

Diamond has long been the material of choice for quantum sensing, but its size limits its applications. Recent research highlights the potential of hBN as an alternative, especially after TMOS researchers have developed ways to stabilize its atomic defects and study its charge states, opening doors for its incorporation into devices that diamond cannot fit.

Diamond has long held the crown in quantum sensing, thanks to its cohesive nitrogen-vacancy centers, adjustable rotation, magnetic field sensitivity, and ability to operate at room temperature. With such a suitable material that is easy to manufacture and its size, there has been little interest in exploring alternatives to diamond.

However, this giant of the quantum field has a security hole. It is simply too big. Much like how an NFL linebacker isn’t a top pick for a jockey in the Kentucky Derby, diamonds fail when delving into quantum sensors and data processing. When the diamond gets very small, the super-stable defect for which it is famous begins to collapse. There is a point at which diamonds become useless.

Enter HPN.

hBN has been overlooked previously as a quantum sensor and quantum information processing platform. This has changed recently when a number of new defects were discovered that constitute a compelling competitor to Diamond’s nitrogen vacancy positions. Among these centers, the boron vacancy center (one missing corn in the hBN crystal lattice) has emerged as the most promising so far.

An experimental setup in TMOS to study boron vacancy defects in hBN. Source: TMOS, ARC Center of Excellence in Transformational Optical Systems

However, they can exist in different charge states and only the -1 charge state is suitable for spin based applications. It has been difficult until now to discover and study other states of charge. This was a problem because the state of charge can flicker, switching between states -1 and 0, making it unstable, especially in the kinds of environments typical of quantum sensors and devices.

But as explained in a paper published in Nano Lettersresearchers from TMOS, the ARC Center of Excellence for Transformational Photonic Systems, have developed a method to stabilize the -1 state, and a new experimental approach to study defect charge states in hBN using optical excitation and synchronized electron beam irradiation.

Lead authors Angus Gale and Dominic Scognamiglio in their research lab. Source: TMOS, ARC Center of Excellence in Transformational Optical Systems

Co-lead author Angus Gill says, “This research shows that hBN has the potential to replace diamond as a preferential material for quantum sensing and quantum information processing because we can stabilize the atomic defects that underpin these applications resulting in 2D layers of hBN that can be embedded in devices that cannot.” to have diamonds in it.”

“We have described this material and discovered very unique and fascinating properties, but the study of hBN is still in its early days,” says co-lead author Dominique Scognamiglio. “There are no other publications about charge-state switching, manipulation, or stabilization of boron vacancies, which is why we are taking the step The first is to bridge this literary gap and better understand this material.

“The next phase of this research will focus on pump-probe measurements that will allow us to optimize defects in hBN for integrated quantum photonics and sensing applications,” says senior investigator Milos Toth.

Quantum sensing is a rapidly advancing field. Quantum sensors have better sensitivity and spatial resolution than conventional sensors. Among its many applications, one of the most important applications of Industry 4.0 and additional device miniaturization is the accurate sensing of temperature as well as electric and magnetic fields in microelectronic devices. Being able to feel these things is the key to controlling them. Thermal management is currently one of the limiting factors in optimizing the performance of miniature devices. Precise quantum sensing nanoscale It will help prevent microchips from overheating and improve performance and reliability.

Quantum sensing also has important applications in medical technology, where its ability to detect nanoparticles and magnetic particles could one day be used as an injectable diagnostic tool looking for cancer cells, or it could monitor metabolic processes in cells to track the effect of cancer cells. Medical treatments.

In order to study boron vacancy defects in hBN, the TMOS team created a new experimental setup that integrates confocal light microscopy with scanning electron microscopy (SEM). This allowed them to simultaneously manipulate the charge states of boron vacancy defects using an electron beam and microelectronic circuits, while measuring the defect.

“This approach is novel because it allows us to focus the laser on and image individual defects in the hBN, while they are processed using electronic circuits and using an electron beam,” says Gale. This modification to the microscope is unique; it has been incredibly useful and has simplified our workflow. Significantly.”

Reference: “Spin defect charge-state manipulation in hexagonal boron nitride” By Angus Gill, Dominik Scognamiglio, Ivan Zegolin, Benjamin Whitefield, Mehran Kiannia, Igor Aharonović, and Milos Toth, 26 Jun. 2023, Available here. Nano Letters.
doi: 10.1021/acs.nanolett.3c01678

The study was funded by the Australian Research Council.