Chen Ruiyang, Luo Yi-Han, Long Jinbao, Shi Baoqi, Shen Chen, Liu Junqiu
International Quantum Academy, Shenzhen 518048, China.
Shenzhen Institute for Quantum Science and Engineering, <a href="https://ror.org/049tv2d57">Southern University of Science and Technology</a>, Shenzhen 518055, China.
Phys Rev Lett. 2024 Aug 23;133(8):083803. doi: 10.1103/PhysRevLett.133.083803.
Photon-pair sources are critical building blocks for photonic quantum systems. Leveraging Kerr nonlinearity and cavity-enhanced spontaneous four-wave mixing, chip-scale photon-pair sources can be created using microresonators built on photonic integrated circuit. For practical applications, a high microresonator quality factor Q is mandatory to magnify photon-pair sources' brightness and reduce their linewidth. The former is proportional to Q^{4}, while the latter is inversely proportional to Q. Here, we demonstrate an integrated, microresonator-based, narrowband photon-pair source. The integrated microresonator, made of silicon nitride and fabricated using a standard CMOS foundry process, features ultralow loss down to 0.03 dB/cm and intrinsic Q factor exceeding 10^{7}. The photon-pair source has brightness of 1.17×10^{9} Hz/mW^{2}/GHz and linewidth of 25.9 MHz, both of which are record values for silicon-photonics-based quantum light source. It further enables a heralded single-photon source with heralded second-order correlation g_{h}^{(2)}(0)=0.0037(5), as well as an energy-time entanglement source with a raw visibility of 0.973(9). Our work evidences the global potential of ultralow-loss integrated photonics to create novel quantum light sources and circuits, catalyzing efficient, compact, and robust interfaces to quantum communication and networks.
光子对源是光子量子系统的关键组成部分。利用克尔非线性和腔增强自发四波混频，可以使用基于光子集成电路构建的微谐振器来创建芯片级光子对源。对于实际应用，高微谐振器品质因数Q对于提高光子对源的亮度和减小其线宽至关重要。前者与Q的四次方成正比，而后者与Q成反比。在此，我们展示了一种基于微谐振器的集成窄带光子对源。该集成微谐振器由氮化硅制成，并采用标准CMOS代工工艺制造，具有低至0.03 dB/cm的超低损耗和超过10^7的固有品质因数Q。该光子对源的亮度为1.17×10^9 Hz/mW^2/GHz，线宽为25.9 MHz，这两个值均为基于硅光子学的量子光源的记录值。它还能够实现具有预示二阶关联g_h^(2)(0)=0.0037(5)的预示单光子源，以及具有原始可见度0.973(9)的能量-时间纠缠源。我们的工作证明了超低损耗集成光子学在创建新型量子光源和电路方面的全球潜力，为量子通信和网络催化高效、紧凑且稳健的接口。
