标题： 量子增强的超越光子对区域的二次谐波生成 显示英文标题

标题： Quantum-enhanced second harmonic generation beyond the photon pairs regime

摘要： 双光子过程在显微镜和微加工等应用中至关重要，但它们的低截面需要强烈的照明，并限制了例如非线性显微镜中的穿透深度。 纠缠态已被提出以提高双光子相互作用的效率，并在低强度下显示出有效性。 这种量子增强通常被认为在高强度下会消失，因为每个模式中超过一个光子，这引发了对其有用性的怀疑。 我们实验和理论上研究了由纠缠光子驱动的超过此阈值强度的双光子过程，并将结果与经典情况进行了比较。 我们发现，在比以前假设的高近一个数量级的强度下，仍可以观察到量子优势。 我们的研究结果表明了在实际应用中利用量子增强的双光子过程的潜在途径。 显示英文摘要

摘要： Two-photon processes are crucial in applications like microscopy and microfabrication, but their low cross-section requires intense illumination and limits, e.g., the penetration depth in nonlinear microscopy. Entangled states have been proposed to enhance the efficiency of two-photon interactions and have shown effectiveness at low intensities. This quantum enhancement is generally believed to be lost at high intensities, for more than one photon per mode, raising doubts about its usefulness. We explored experimentally and theoretically two-photon processes driven by entangled photons at intensities beyond this threshold and compared the results with the classical case. We found that a quantum advantage can still be observed at nearly one order of magnitude higher intensities than previously assumed. Our findings show a potential path for exploiting quantum-enhanced two-photon processes in practical applications.