Nanophotonic platforms have multiple properties and features desirable for producing correlated photon pairs. In these platforms, spontaneous parametric down-conversion (SPDC) and spontaneous four-wave-mixing (SFWM) have been used to achieve photon pair production. By placing the nonlinear region in a resonant cavity, the source obtains an enhanced nonlinear interaction and naturally filters out photons by frequency according to the cavity linewidth. Among various platforms, X-cut thin-film lithium niobate (TFLN) stands out for its strong second-order optical nonlinearity (
χ(2)) and access to a strong platform for modulating light. Although previously demonstrated, present sources are limited in their photon pair channel availability, limiting the potential of quantum applications in quantum information processing, communication, and sensing that can scale in robustness by having access to multiple photon pair channels. To this end, we demonstrate a photon pair source on X-cut TFLN with 80 measured photon pair channels spanning the C and L optical bands with a frequency spacing of 49.5 GHz between photons. We characterize the second-order correlation function and pair generation rate (PGR) of 80 channels, the highest number of channels demonstrated to date, and achieve a pair generation of 125.7 kHz / μW after accounting for the cavity's escape efficiency. We also demonstrate heralded single photon operation by calculating a heralded auto-correlation dip of 0.0544
± 0.0054 with 2.2 mW of on-chip pump power. These findings demonstrate the promise of X-cut TFLN as a strong platform for quantum optical applications.
Efficient interfaces of quantum emitters and photons are fundamental to quantum networking. Silicon-vacancy (SiV) centers embedded in diamond nanophotonics are a leading approach due to their excellent optical and spin coherence; however, diamond’s weak nonlinearity and challenging fabrication limit long-term scalability. Here, we realize the first high-cooperativity ( C >1) coupling of individual SiV spin qubits in a scalable, hybrid-integrated gallium phosphide (GaP)-on-diamond nanophotonics platform. We fabricate more than 600 GaP nanophotonic cavities on a diamond substrate with a 99.5% yield. We confirm above-unity cooperativity and measure spin-relaxation times exceeding 0.4 ms at 4 K, which together enable single-shot readout of the SiV electron spin. These results, coupled with GaP’s strong nonlinear properties, establish GaP-on-diamond as a scalable planar platform for quantum networking applications.
We demonstrate the tunable quantum beat of single photons through the co-development of core nonlinear nanophotonic technologies for frequency-domain manipulation of quantum states in a common physical platform. Spontaneous four-wave mixing in a nonlinear resonator is used to produce non-degenerate, quantum-correlated photon pairs. One photon from each pair is then frequency shifted, without degradation of photon statistics, using four-wave mixing Bragg scattering in a second nonlinear resonator. Fine tuning of the applied frequency shift enables tunable quantum interference of the two photons as they are impinged on a beamsplitter, with an oscillating signature that depends on their frequency difference. Our work showcases the potential of nonlinear nanophotonic devices as a valuable resource for photonic quantum information science.