新方法彻底改变量子信息跨波长传输

诸平

Fig. 1 Researchers at SJTU have developed a novel method for broadband frequency conversion, enhancing data transfer and quantum networks through improved optical processing. Credit: SciTechDaily.com

Fig. 2 (a) Schematic of the birefringent racetrack resonator on X-cut TFLN, where SH-band light experiences a mode-hybridization in the half-circle waveguide. (b) Principle of SQPM. Inset: varying SQPM SHG intensity with the periodically inverted efficient nonlinear coefficient (m=5), and a comparison among the SHG processes under the perfect phase-matching (PPM), QPM, SQPM, and phase mismatching (PMM). (c) Effective refractive indices of the hybrid mode in SH-band and TE0 mode in FW-band in the half-circle waveguide, and the vector mismatch dispersion between them. (d) Average vector mismatch dispersion versus different FW wavelengths, which is positive in the straight waveguide and negative in the half-circle waveguide. Credit: T. Yuan, J. Wu, et al., doi 10.1117/1.AP.6.5.056012

Fig. 3 Dispersion-designed structural geometry enables group-velocity mismatch of interacting lights to be smoothed to zero, for wide-range frequency conversion. Credit: T. Yuan, J. Wu, et al., doi 10.1117/1.AP.6.5.056012

据国际光学与光子学学会(International Society for Optics and Photonics)2024年10月28日提供的消息，新方法彻底改变量子信息跨波长传输(New Method Revolutionizes Quantum Information Transfer Across Wavelengths)。

最近在频率转换方面的突破已经实现了可观的带宽，为更有效的量子信息传输和先进的集成光子系统开辟了新的可能性。

量子信息技术（quantum information technology）的进步正在实现更快、更有效的数据传输。然而，一个主要的挑战在于将量子信息的基本单位量子比特（qubits）传输到不同波长，同时保持它们的关键特性，如相干性和纠缠性。

据《先进光子学》（Advanced Photonics）报道，中国上海交通大学（Shanghai Jiao Tong University 简称SJTU）的研究人员最近在这一领域取得了重大进展，他们开发了一种新的宽带频率转换方法，这是未来量子网络的关键一步。原文详见：Tingge Yuan, Jiangwei Wu, Xueyi Wang, Chengyu Chen, Hao Li, Bo Wang, Yuping Chen, Xianfeng Chen. Chip-scale nonlinear bandwidth enhancement via birefringent mode hybridization. Advanced Photonics, 2024, 6(5): 056012. DOI: 10.1117/1.AP.6.5.056012. Published online 18 September 2024. https://www.researching.cn/ArticlePdf/m00090/2024/6/5/056012.pdf

参与此项研究的除了来自上海交通大学物理与天文学院，先进光通信系统与网络国家重点实验室（Shanghai Jiao Tong University, School of Physics and Astronomy, State Key Laboratory of Advanced Optical Communication Systems and Networks, Shanghai, China）的研究人员之外，还有来自山东师范大学光操纵与应用协同创新中心（Shandong Normal University, Collaborative Innovation Center of Light Manipulations and Applications, Jinan, China）的研究人员。

上海交通大学（SJTU）的团队专注于使用X切割薄膜铌酸锂（thin film lithium niobate简称TFLN）的技术，TFLN这种材料以其非线性光学特性而闻名。他们实现了宽带二次谐波产生，这是将光从一个波长转换为另一个波长的重要过程，其带宽高达13纳米（13 nm）。这是通过一种称为模式杂化的过程完成的，该过程允许在微赛道谐振器（micro-racetrack resonator）中精确控制频率转换。

该技术的广泛应用(Wide Applications of the Technology)

上述论文的通讯作者陈玉萍教授(Professor Yuping Chen)表示，由于在波分复用网络（wavelength division multiplexing networks）、超短脉冲非线性（ultrashort pulse nonlinearity）、量子密钥分配（quantum key distribution）和宽带单光子源生成（broadband single-photon source generation）等领域的广泛应用，具有广泛可调泵浦带宽的高效二阶非线性过程一直是人们追求的目标。”

她补充说：“由于TFLN平台制造技术的巨大进步，这项工作将为超短光脉冲甚至量子态之间的芯片级非线性频率转换铺平道路。”

这一突破可能对集成光子系统产生广泛的影响。通过实现芯片上可调频率转换，它为增强量子光源、更大容量复用和更有效的多通道光信息处理打开了大门。随着研究人员继续探索这些技术，扩展量子信息网络的潜力不断增长，使我们更接近实现其在各种应用中的全部功能。

本研究得到了中国国家自然科学基金{ National Natural Science Foundation of China (Grant No. 12134009)}、中国国家重点研发计划{National KeyR&D Program of China (Grant No. 2019YFB2203501)}以及中国上海交通大学{ SJTU (Grant No. 21X010200828)}的资助。

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Abstract

On-chip quantum information network requires qubit transfer between different wavelengths while preserving quantum coherence and entanglement, which requires the availability of broadband upconversion. Herein, we demonstrate a mode-hybridization-based broadband nonlinear frequency conversion on X-cut thin film lithium niobate. With the spontaneous quasi-phase matching and quasi-group-velocity matching being simultaneously satisfied, broadband second-harmonic generation with a 3-dB bandwidth up to 13 nm has been achieved in a micro-racetrack resonator. The same mechanism can work on the frequency conversion of the ultrashort pulse in the bent waveguide structure. This work will be beneficial to on-chip tunable frequency conversion and quantum light source generation on integrated photonic platforms and further enable on-chip large-capacity multiplexing, multichannel optical information processing, and large quantum information networks.