Hu and Colleagues Demonstrate 0.943 Efficiency Photonic Platform for Quantum Information Processing
Integrated photonic circuits create scalable and robust quantum technologies by combining photon sources and linear optical networks on compact chips. Yi-Han Luo and colleagues at International Quantum Academy and Shenzhen Futian SUSTech Institute for Quantum Technology and Engineering and University of Science and Technology of China and Southern University of Science and Technology have addressed a key limitation in these systems, optical loss, by demonstrating a monolithic silicon nitride platform for discrete-variable quantum information processing. Their architecture achieves high-fidelity Einstein-Podolsky-Rosen (EPR) states (0.9875 ±0.0003) and near-unity photon indistinguishability, enabling the synthesis and characterisation of four-photon Greenberger-Horne-Zeilinger states with a record fidelity of 0.943 ±0.008 and a fourfold count rate of 27Hz. This represents a substantial advance over previous silicon-photonic implementations. These results, combined with CMOS-compatible fabrication, position ultralow-loss silicon nitride integrated photonics as a viable platform for large-scale, deployable quantum processors. High-rate multi-photon entanglement achieved via integrated silicon nitride photonics A fourfold count rate of 27Hz for four-photon Greenberger-Horne-Zeilinger states represents a new level of performance, exceeding previous silicon-photonic implementations by more than two orders of magnitude. This significant threshold overcomes the rate-loss barrier that previously prevented the creation of complex multi-photon states essential for scalable quantum computing. Prior quantum photonic systems often struggled to reliably generate even single entangled photons, limiting the complexity of quantum algorithms that could be implemented. The fundamental challenge lies in maintaining the fragile quantum state of photons as they propagate through optical circuits, with losses rapidly degrading the signal. The silicon nitride platform integrates essential c
