Researchers create 2D quantum light source from layered materials

Researchers create 2D quantum light source from layered materials


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Recent advances in spontaneous parametric down-conversion (SPDC)-based quantum light sources based on two-dimensional layered materials have been made by a team led by Prof. Ren Xifeng of the University of Science and Technology of China (USTC), the Chinese Academy of Sciences, in Cooperation with Prof. Qiu Chengwei and Dr. Guo Qiangbing from the National University of Singapore (NUS). The study was published in Nature.

Miniaturization and integration are strategies widely used in optical quantum systems to improve their scalability and stability, thus providing a route to scalable and practical solutions for optical quantum computing and quantum communication.

In this study, researchers reported a van der Waals crystal (NbOCl2) with monolayer-like excitonic behavior in bulk form, indicating verified weak electronic coupling between the layers. Theoretical calculations implied that such weak interlayer coupling originated from the strong ionic Nb-Cl bonding in the crystal.

Second harmonic generation (SHG) is the lowest order nonlinear optical process in which the second order nonlinear optical susceptibility is responsible for the production of light at the second harmonic frequency. Despite a high second-order nonlinear susceptibility, conventional 2D materials (e.g. WS2) show a decreasing SHG response with increasing layer number, while the SHG intensity is scalable in NbOCl2 is up to three orders of magnitude higher than with monolayer WS2.

Remarkably, this newly reported crystal flake is only 46 nm thin. The strong second-order nonlinearity of crystalline NbOCl2 enables an SPDC process, a second-order nonlinear process in which a photon is converted into a pair of photons by a powerful pump laser, meaning that the detection of one photon of the pair announces the presence of the other.

The discovery makes crystalline NbOCl2 both the thinnest and the first two-dimensional SPDC source ever reported.

The results of this study not only provide an integrable quantum light source for optical quantum information technology, but also open a new direction in the study of optical nonlinearity in two-dimensional materials.

More information:
Qiangbing Guo et al, Ultrathin Quantum Light Source Using van der Waals NbOCl2 Crystal, Nature (2023). DOI: 10.1038/s41586-022-05393-7

Provided by the Chinese Academy of Sciences

Citation: Researchers create 2D quantum light source from layered materials (2023 January 19) Retrieved January 19, 2023 from

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