美国加州理工学院Kerry Vahala团队研究了高Q氮化硅微谐振器中的下转换光子对。该研究于2025年3月19日发表在《自然》杂志上。

自发参量下转换（SPDC）产生的纠缠光子对是许多量子应用的核心。SPDC通常在具有固有二阶非线性（χ^（2））的非中心对称系统中执行。研究组在Si₃N₄中展示了强窄带SPDC，片上速率为每秒80万对。Si₃N₄是光子集成的卓越材料，也表现出最低的波导损耗（这对集成量子电路至关重要）。然而，氮化硅是非晶的，缺乏内在的χ^（2），这限制了它在光子量子器件中的作用。

研究组通过将高光学Q因子微腔内的强光场增强与光学诱导的空间电荷场相结合，在Si₃N₄中实现了SPDC。他们提出了具有高光谱亮度的窄带光子对。通过重合测量验证了下转换光子对的量子性质。这种基于Si₃N₄集成光子技术的光源为芯片上的量子系统开辟了新的途径。

附：英文原文

Title: Down-converted photon pairs in a high-Q silicon nitride microresonator

Author: Li, Bohan, Yuan, Zhiquan, Williams, James, Jin, Warren, Beckert, Adrian, Xie, Tian, Guo, Joel, Feshali, Avi, Paniccia, Mario, Faraon, Andrei, Bowers, John, Marandi, Alireza, Vahala, Kerry

Issue&Volume: 2025-03-19

Abstract: Entangled photon pairs from spontaneous parametric down-conversion (SPDC)1 are central to many quantum applications2,3,4,5,6. SPDC is typically performed in non-centrosymmetric systems7 with an inherent second-order nonlinearity (χ(2))8,9,10. We demonstrate strong narrowband SPDC with an on-chip rate of 0.8 million pairs per second in Si3N4. Si3N4 is the pre-eminent material for photonic integration and also exhibits the lowest waveguide loss (which is essential for integrated quantum circuits). However, being amorphous, silicon nitride lacks an intrinsic χ(2), which limits its role in photonic quantum devices. We enabled SPDC in Si3N4 by combining strong light-field enhancement inside a high optical Q-factor microcavity with an optically induced space-charge field. We present narrowband photon pairs with a high spectral brightness. The quantum nature of the down-converted photon pairs is verified through coincidence measurements. This light source, based on Si3N4 integrated photonics technology, unlocks new avenues for quantum systems on a chip.

DOI: 10.1038/s41586-025-08662-3

Source: https://www.nature.com/articles/s41586-025-08662-3