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Scalable quantum photonic devices drive the development of compact sources of entangled photons, which are pivotal for quantum communication, computing, and cryptography. In this work, we present entangled photon pair generation in rhombohedral boron nitride (r-BN), leveraging its unique optical and structural properties. Unlike conventional hexagonal boron nitride, which suffers from reduced nonlinear response due to centrosymmetric structure in even-layered stacks, r-BN features interlayer ABC stacking and maintains robust in-plane inversion symmetry. These characteristics lead to highly efficient entangled photon generation. Our system demonstrates an entangled photon pair generation rate up to 8667 Hz/(mW·mm) and offers a tunable platform for Bell state generation by simply adjusting the pump polarization, without compromising the entanglement quality or generation efficiency. The polarization entangled state is measured with a fidelity up to 94%. This advancement not only marks a significant step towards ultrathin, scalable quantum devices but also establishes r-BN as a promising candidate for on-chip integrated quantum optical applications.
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http://dx.doi.org/10.1038/s41467-025-56436-2 | DOI Listing |
Nat Photonics
June 2025
University of Vienna, Faculty of Physics, Vienna Center for Quantum Science and Technology (VCQ), Vienna, Austria.
Recently, machine learning has had remarkable impact in scientific to everyday-life applications. However, complex tasks often require the consumption of unfeasible amounts of energy and computational power. Quantum computation may lower such requirements, although it is unclear whether enhancements are reachable with current technologies.
View Article and Find Full Text PDFNanoscale Horiz
September 2025
Theoretical Chemical Physics Group, Research Institute for Materials Science and Engineering, University of Mons, 20 Place du Parc, Mons B-7000, Belgium.
Two-photon spontaneous emission (TPSE) is a second-order quantum process with promising applications in quantum optics that remains largely unexplored in molecular systems, which are usually very inefficient emitters. In this work, we model the first molecular two-photon emitters and establish the design rules, highlighting their differences from those governing two-photon absorbers. Using both time-dependent density functional theory and Pariser-Parr-Pople calculations, we calculate TPSE in three π-conjugated molecules and identify a dominant pathway.
View Article and Find Full Text PDFAdv Mater
September 2025
School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
Molecular spin systems that can be chemically tuned, coherently controlled, and readily integrated within devices remain central to the realization of emerging quantum technologies. Organic high-spin materials are prime candidates owing to their similarity in electronic structure to leading solid-state defect-based systems, light element composition, and the potential for entanglement and qubit operations mediated through spin-spin exchange. However, the inherent instability of these species precludes their rational design, development, and application.
View Article and Find Full Text PDFLight Sci Appl
September 2025
John A. Paulson School of Engineering and Applied Sciences, Harvard University, 9 Oxford Street, Cambridge, MA, 02138, USA.
Entanglement is paramount in quantum information processing. Many quantum systems suffer from spatial decoherence in distances over a wavelength and cannot be sustained over short time periods due to dissipation. However, long range solutions are required for the development of quantum information processing on chip.
View Article and Find Full Text PDFSci Adv
September 2025
School of Physical and Chemical Sciences, University of Canterbury, Christchurch 8140, New Zealand.
High-precision, Sagnac interferometry has long been proposed as a route to test fundamental questions in physics such as the magnitude of relativistic precessions (e.g., the Lense-Thirring effect).
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