近日，中山大学刘进团队研究了量子点自发双光子发射的量子相关性。相关论文于2025年7月9日发表在《自然》杂志上。

自发双光子发射（STPE）是一种二阶量子辐射过程，在天体物理学、原子物理学和量子技术中具有重要意义。特别是，单量子发射体的按需STPE长期以来一直被预测将彻底改变光子量子科学和技术。

研究组报告了STPE的亮度与单个半导体量子点与高质量微柱腔确定性耦合的竞争单光子辐射相当。这是由于微腔中强烈的真空波动导致双激子直接进入基态。研究组在以光子统计测量为主题的腔量子电动力学体系中展示了与STPE相关的量子性质。

此外，STPE还被用于构建非常规纠缠量子光阱，该量子光阱可以同时实现自发参量下转换光阱的近单位纠缠保真度和原子量子发射体的按需光子发射。该工作提供了对量子状态下双光子过程的见解，这可能使光子量子技术具有非线性量子辐射。

附：英文原文

Title: Quantum correlations of spontaneous two-photon emission from a quantum dot

Author: Liu, Shunfa, Wang, Yangpeng, Saleem, Yasser, Li, Xueshi, Liu, Hanqing, Yang, Cheng-Ao, Yang, Jiawei, Ni, Haiqiao, Niu, Zhichuan, Meng, Yun, Hu, Xiaolong, Yu, Ying, Wang, Xuehua, Cygorek, Moritz, Liu, Jin

Issue&Volume: 2025-07-09

Abstract: Spontaneous two-photon emission (STPE) is a second-order quantum radiation process with implications in astrophysics1, atomic physics2 and quantum technology3. In particular, on-demand STPE from single quantum emitters has long been predicted to revolutionize photonic quantum science and technology4,5. Here we report STPE with brightness comparable to that of competing single-photon radiation from a single semiconductor quantum dot deterministically coupled to a high-quality micropillar cavity. This is because of strong vacuum fluctuations in the microcavity, which drive a biexciton directly to the ground state. We show the quantum nature associated with STPE in the cavity quantum electrodynamics regime using photon statistics measurements. Furthermore, STPE is exploited to build unconventional entangled quantum light sources that can simultaneously achieve near-unity entanglement fidelity for spontaneous parametric down-conversion sources and on-demand photon emission for atomic quantum emitters. Our work provides insights into the two-photon process in the quantum regime, which could empower photonic quantum technology with nonlinear quantum radiation.

DOI: 10.1038/s41586-025-09267-6

Source: https://www.nature.com/articles/s41586-025-09267-6