The researchers achieved coherent control of the spin defects of two-dimensional solid materials

(Nanowerk News) In the breakthrough achievement arranged by Professor Guo Guangcan’s team in partnership with Wigner Physics Research Center, an innovative method has been introduced which uncovers novel spin defects with an impressive probability of 85%. In addition, the team has managed to perform coherent control of highly bright single spins in hexagonal boron nitride (hBN) at ambient temperature.

The results of their research have been shared with the scientific community through publications in Nature Communications (“Coherent control of single spin ultrabright in hexagonal boron nitride at room temperature”).

Spin defects in solids are very significant in the quantum information realm. A prominent example is the nitrogen vacancy centers (NV) found in diamond, a feature that has been widely used in quantum computing and quantum networks. Hexagonal boron nitride (hBN), a two-dimensional material, is highly regarded as an excellent host for color center spin defects. Spin defects in hBN have generated significant interest because of their beneficial applications in two-dimensional quantum devices and integrated quantum nanodevices.

In the spin defect field identified in hBN, negatively charged boron vacancies (VB–) defects have emerged as the most common. Previous research conducted by Professor Guo’s team investigated temperature dependence measurements based on VB– disabled (ACS Photonics, “Temperature-Dependent Energy Level Shifts of Spin Defects in Hexagonal Boron Nitride”), and highlights the coherent dynamics of the multi-spin VB– middle (Nature Communications, “Coherent dynamics of multi-spin V−B centers in hexagonal boron nitride”). Their exploration, however, showed difficulty in detecting a single VB– flawed due to its low quantum efficiency for optical transitions. While several studies have reported increased photoluminescence of VB– defects, practical observations and coherent single-turn control remain a complex challenge.

In a recent study, researchers succeeded in isolating individual color centers in hBN powder samples using capillary force as a relief mechanism. This led to the discovery of a very bright single-spin color center category with an overwhelming success rate of 85%, indicating a 21-fold improvement compared to the previous methodology.

After 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 amount of fluorescence from a single spin color center ever reported in hBN. They also identified the Rabi oscillation signal and performed the Hahn echo experiment. This breakthrough marks the first instance of a single spin color center in hBN being manipulated at room temperature, heralding a new age in quantum information applications.

Next, the team used first principles calculations to gain clarity on the structure of these color center defects. Their investigation showed that the carbon-oxygen dopant complex is a potential origin of this kind of single-spin color center defect. The simulated optically detected magnetic resonance spectrum (ODMR) of CNCB3 the model was found to be in line with the experimental results.

The successful coherent control of a single extraordinarily bright spin in hBN at room temperature signifies a quantum leap in quantum science, thereby opening up the possibility for controlling optically manipulated spins.