Introducing Quantum Sensors into Diamonds

Researchers have now discovered the possibility of creating dense ensembles of quantum spins in diamonds with high resolution by using an electron microscope, making the way for refined sensors and resources for quantum technologies.

This photo shows a diamond sample illuminated by green light in home-built microscope. The sample is placed on a special mount, within a printed circuit board, used to deliver microwaves which allow quantum manipulations and magnetic sensing with the NVs. CREDIT (Credit: Yoav Romach)

Diamonds are made up of carbon atoms in a crystalline structure, but if a carbon atom is replaced with a different type of atom, this will lead to a lattice defect. One such defect refers to the Nitrogen-Vacancy (NV), in which one carbon atom is replaced by a nitrogen atom, and its neighbor is missing, wherein an empty space remains in its place.

Illuminating this defect with a green laser will result in it emitting red light (fluoresce) with an interesting feature: its intensity differs based on the magnetic properties in the environment. This unique feature allows the NV center to be chiefly useful for measuring magnetic fields, quantum computing and information, and magnetic imaging (MRI).

To produce optimal magnetic detectors it is necessary to increase the density of these defects without increasing environmental noise and destroying the diamond properties.

Presently, scientists from the research group of Nir Bar-Gill at the Hebrew University of Jerusalem's Racah Institute of Physics and Department of Applied Physics, in association with Prof. Eyal Buks of the Technion - Israel Institute of Technology, have demonstrated that ultra-high densities of NV centers can be attained by a simple process of employing electron beams in order to kick carbon atoms out of the lattice.

This work, featured in the scientific journal Applied Physics Letters, is considered to be a continuation of earlier work in the field, and shows advancement in the densities of NV centers in a wide range of diamond types. The irradiation is carried out using an electron beam microscope (Transmission Electron Microscope (TEM)), which has been particularly transformed for this purpose. The availability of this device in nanotechnology centers in a number of universities in Israel and all over the world assists this process with high spatial accuracy, rapidly and simply.

The improved densities of the NV color centers obtained, while maintaining their exceptional quantum properties, suggest future enhancements in the sensitivity of diamond magnetic measurements, and also promising directions in the study of quantum information theory and solid state physics.

Nitrogen Vacancy (NV) color centers display unique and remarkable properties, including long coherence times at room temperature (~ ms), coherent microwave control, and optical initialization and readout.

"This work is an important stepping stone toward utilizing NV centers in diamond as resources for quantum technologies, such as enhanced sensing, quantum simulation and potentially quantum information processing", stated Bar-Gill, an Assistant Professor in the Dept. of Applied Physics and Racah Institute of Physics at the Hebrew University, where he founded the Quantum Information, Simulation and Sensing lab.

What is special about our approach is that it's very simple and straightforward. You get sufficiently high NV concentrations that are appropriate for many applications with a simple procedure that can be done in-house.

Dima Farfurnik, Researcher, Hebrew University

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