We report the symmetry-dependent intensity–noise correlation and the intensity-difference squeezing of spontaneous parametric four-wave mixing (SP-FWM) and fluorescence (FL) hybrid signals from the different phases [hexagonal (H) + tetragonal (T), T + H] of Pr³⁺: YPO₄ and Eu³⁺: YPO₄ crystals. The competition between FL and SP-FWM in hybrid signals determines the amplitude and hybrid line shape of the two-mode and three-mode correlation. The correlation amplitude switches from positive to negative due to strong double dressing caused by a high transition probability and a dipole moment of the (more H + less T)-phase of Pr³⁺: YPO₄. This switching phenomenon is used to realize a metal–oxide semiconductor field-effect transistor-based logic inverter. Furthermore, the line shape of correlation changes from broad to sharp due to weak dressing, transition probability, and a low dipole moment of the (more T + less H)-phase of Pr³⁺: YPO₄. Based on these results, we proposed the model of a tunable correlation filter. Gate position, frequency detuning, and laser power control the amplitude and hybrid line shape. Our experimental results provide an advanced technique of bandwidth contrast of about 0.9%. Such notch filters have potential applications in quantum communications.

中文翻译：

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Pr3+: YPO4 和 Eu3+: YPO4 相关和压缩的可控混合线形状的相变滤波器

我们报告了来自不同相 [六边形 (H) + 四边形 (T), Pr ³⁺ : YPO ₄和Eu ³⁺ : YPO ₄晶体的T + H] 。混合信号中FL和SP-FWM之间的竞争决定了二模和三模相关的幅度和混合线形状。由于高跃迁概率和 Pr ³⁺ : YPO ₄ (更多 H + 更少 T) 相的偶极矩引起的强双重修整，相关幅度从正变为负. 这种开关现象用于实现基于金属氧化物半导体场效应晶体管的逻辑逆变器。此外，由于 Pr ³⁺ : YPO ₄的（更多 T + 更少 H）-相位的弱修整、跃迁概率和低偶极矩，相关的线形从宽变尖锐。基于这些结果，我们提出了可调相关滤波器的模型。栅极位置、频率失谐和激光功率控制幅度和混合线形状。我们的实验结果提供了一种带宽对比度约为 0.9% 的先进技术。这种陷波滤波器在量子通信中具有潜在的应用。