Researchers achieve coherent control of two-dimensional material solid-state spin defects

(Nanowerk News) In a groundbreaking achievement orchestrated by Professor Guo Guangcan's team in partnership with the Wigner Research Centre for Physics, an innovative method has been introduced which uncovers a novel spin defect with an impressive likelihood of 85%. In addition, the team has succeeded in carrying out coherent control of an extremely bright, singular spin in hexagonal boron nitride (hBN) at ambient temperature.
The results of their research have been shared with the scientific community through a publication in Nature Communications ("Coherent control of an ultrabright single spin in hexagonal boron nitride at room temperature").
Spin defects in solid-state substances are critically significant in the realm of quantum information. A prominent example is the nitrogen-vacancy (NV) center found in diamonds, a feature that has found extensive use in quantum computing and quantum networks. Hexagonal boron nitride (hBN), a two-dimensional material, is highly regarded as an exceptional host for color-center spin defects. The spin defects in hBN have elicited significant interest due to their beneficial applications in two-dimensional quantum devices and integrated quantum nanodevices.
Within the sphere of spin defects identified in hBN, the negatively charged boron vacancy (VB-) defect has emerged as the most commonplace. Earlier research carried out by Professor Guo's team investigated the temperature dependence measurement based on the VB- defect (ACS Photonics, "Temperature-Dependent Energy-Level Shifts of Spin Defects in Hexagonal Boron Nitride"), and highlighted the coherent dynamics of the multi-spin VB- center (Nature Communications, "Coherent dynamics of multi-spin V−B center in hexagonal boron nitride"). Their exploration, however, indicated the difficulty in detecting a single VB- defect due to its low quantum efficiency for the optical transition. While some studies have reported increased photoluminescence of the VB- defect, the practical observation and control of a single coherent spin remains a complex challenge.
In this recent study, the researchers successfully isolated individual color centers in hBN powder samples using capillary force as an assisting mechanism. This led to the discovery of a category of extremely bright, single-spin color centers with an outstanding success rate of 85%, signifying a 21-fold enhancement compared to previous methodologies.
Upon determining the optical properties of these color centers, the researchers noticed significant antibunching features and photon emissivity reaching up to 25 MHz, marking the highest fluorescence count of single spin color centers ever reported in hBN. They also identified the Rabi oscillation signal and carried out Hahn echo experiments. This breakthrough marked the first instance of a single-spin color center in hBN being manipulated at room temperature, signifying a new epoch in quantum information application.
Furthermore, the team employed first principles calculations to gain clarity about the structure of this color-center defect. Their investigation suggested that a complex of carbon-oxygen dopants could potentially be the origin of this kind of single-spin color-center defects. The simulated optically detected magnetic resonance (ODMR) spectra of the CNCB3 model were found to be in alignment with the experimental outcomes.
The successful coherent control of an extraordinarily bright, singular spin in hBN at room temperature signifies a quantum leap in quantum science, thereby opening up possibilities for controlling spins that can be optically manipulated.
Source: Chinese Academy of Sciences (Note: Content may be edited for style and length)
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