Terahertz (THz)-bandwidth continuous-wave (CW) squeezed light is essential for integrating quantum processors with time-domain multiplexing (TDM) by using optical delay line interferometers. Here, we utilize a single-pass optical parametric amplifier (OPA) based on a single-spatial-mode periodically poled ZnO:LiNbO₃ waveguide, which is directly bonded onto a LiTaO₃ substrate. The single-pass OPA allows THz bandwidth, and the absence of higher-order spatial modes in the single-spatial-mode structure helps avoid degradation of squeezing. In addition, the directly bonded ZnO-doped waveguide has durability for high-power pump and shows small photorefractive damage. Using this waveguide, we observe CW 6.3-dB squeezing at 20-MHz sideband by balanced homodyne detection. This is the first realization of CW squeezing with a single-pass OPA at a level exceeding 4.5 dB, which is required for the generation of a two-dimensional cluster state. Furthermore, the squeezed light shows 2.5-THz spectral bandwidth. The squeezed light will lead to the development of a high-speed on-chip quantum processor using TDM with a centimeter-order optical delay line.

中文翻译：

---

来自单模PPLN波导的带宽为2.5 THz的连续波压缩6 dB的光

太赫兹（THz）带宽连续波（CW）压缩的光对于使用光延迟线干涉仪将量子处理器与时域多路复用（TDM）集成在一起至关重要。在这里，我们利用基于单空间模式周期性极化ZnO：LiNbO ₃波导的单通光学参量放大器（OPA），该波导直接键合到LiTaO _3上基质。单通道OPA允许THz带宽，并且单空间模式结构中不存在高阶空间模式有助于避免压缩性能下降。此外，直接键合的ZnO掺杂的波导具有高功率泵浦的耐用性，并且光折射损害小。使用该波导，我们通过平衡零差检测观察到在20 MHz边带处的CW 6.3 dB压缩。这是单通道OPA以超过4.5 dB的电平进行CW压缩的第一个实现，这是生成二维簇状态所必需的。此外，被压缩的光显示出2.5-THz的光谱带宽。压缩的光将导致开发使用带有厘米级光学延迟线的TDM的高速片上量子处理器。