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arXiv · 2605.14592

Entangled Telecom Photon Generation using Twisted Van der Waals Crystals

Nidhin Prasannan·Konstantinos Mourzidis·Vishwas Jindal·Hanting Li·Di Lin·Wenchen Yang·Deng Hu·Liu Yang·Andrea Balocchi·Delphine Lagarde·Pierre Renucci·Zhiwei Wang·Gang Wang·Xavier Marie
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Abstract

Nanoscale quantum light sources are essential building blocks for integrated quantum photonic systems. Here, we report a wavelength-scale entangled-photon source based on van der Waals-engineered NbOBr$_2$, and benchmark its performance for telecom-wavelength quantum light generation. By exploiting the material's second-order nonlinearity, we generate quantum-correlated photon pairs via spontaneous parametric down-conversion. We then use a 90$^{\circ}$ twisted stacking to induce quantum interference in photon-pair generation, yielding polarization-entangled photons. This approach enables tunability of the quantum optical state via control of the excitation laser polarization. We experimentally obtain entanglement fidelities exceeding 95% for Bell states, along with a high coincidence-to-accidental ratio of $\sim$335, and a brightness approximately one order of magnitude higher than recently reported telecom sources based on transition metal dichalcogenide (TMD) 2D materials. These results establish twisted van der Waals engineering as a powerful platform for highly tunable, high-brightness quantum light sources at telecom wavelengths.

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Nidhin Prasannan, Konstantinos Mourzidis, Vishwas Jindal, Hanting Li, Di Lin, Wenchen Yang, Deng Hu, Liu Yang, Andrea Balocchi, Delphine Lagarde, Pierre Renucci, Zhiwei Wang, Gang Wang, Xavier Marie. 2026-05-14. Entangled Telecom Photon Generation using Twisted Van der Waals Crystals. https://arxiv.org/abs/2605.14592

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