量子技術の新たな道を開く：連続変数統合量子フォトニクスの発展（Blazing new trails for quantum technology: PKU kindles the light for continuous-variable integrated quantum photonics）

2025-02-27 北京大学（PKU）

＜関連情報＞

• https://newsen.pku.edu.cn/news_events/news/research/14746.html
• https://www.nature.com/articles/s41586-025-08602-1

集積マイクロコームにおける連続可変多部位エンタングルメント Continuous-variable multipartite entanglement in an integrated microcomb

Xinyu Jia,Chonghao Zhai,Xuezhi Zhu,Chang You,Yunyun Cao,Xuguang Zhang,Yun Zheng,Zhaorong Fu,Jun Mao,Tianxiang Dai,Lin Chang,Xiaolong Su,Qihuang Gong & Jianwei Wang
Nature  Published:19 February 2025
DOI:https://doi.org/10.1038/s41586-025-08602-1

Abstract

The generation of large-scale entangled states is crucial for quantum technologies, such as quantum computation¹, communication² and metrology³. Integrated quantum photonics that enables on-chip encoding, processing and detection of quantum light states offers a promising platform for the generation and manipulation of large-scale entangled states^4,5. Generating entanglement between qubits encoded in discrete variables within single photons is challenging, owing to the difficulty of making single photons interact on photonic chips^{6,7,8,9,10,11}. Devices that operate with continuous variables are more promising, as they enable the deterministic generation and entanglement of qumodes, in which information is encoded in light quadratures. Demonstrations so far have been limited to entanglement between two qumodes^{12,13,14,15,16,17,18,19,20}. Here we report the deterministic generation of a continuous-variable eight-mode entanglement on an integrated optical chip. The chip delivers a quantum microcomb that produces multimode squeezed-vacuum optical frequency combs below the threshold. We verify the inseparability of our eight-mode state and demonstrate supermode multipartite entanglement over hundreds of megahertz sideband frequencies through violation of the van Loock–Furusawa criteria. By measuring the full matrices of nullifier correlations with sufficiently low off-diagonal noises, we characterize multipartite entanglement structures, which are approximate to the expected cluster-type structures for finite squeezing. This work shows the potential of continuous-variable integrated photonic quantum devices for facilitating quantum computing, networking and sensing.