Subnanometer resolution quantum metrology via metasurface mode decomposition

The pressing demand for sub-nanometer displacement metrology in advanced fields, such as semiconductor manufacturing, challenges conventional optical techniques, which are often limited by the diffraction limit and environmental susceptibility. Here, we propose and experimentally demonstrate a novel precision metrology approach based on quantum mode decomposition. By designing a regionally modulated metasurface, we convert an incident fundamental Gaussian beam into higher-order spatial modes that are highly sensitive to positional shifts. We measure displacement by detecting the resulting changes in mode coupling efficiency, experimentally achieving an ultra-high resolution of 0.21nm. This method surpasses the diffraction limit without requiring long-path interferometry, offering significant advantages in terms of system integration and environmental robustness. It provides a new pathway for applications in ultra-precision manufacturing and quantum measurement, demonstrating considerable potential.