Achieving quantum-limited optical resolution with degenerate spatial modes
Xiao-Jie Tan · Physical Review Applied · 2025
Superresolution imaging can be achieved through the exploration and implementation of optimal measurements that attain the fundamental quantum bound. To this end, degenerate optical-mode demultiplexing is proposed as a quantum optimal measurement for resolving two incoherent optical point sources in two-dimensional space. By projecting photons into degenerate subspaces of spatial modes, quantum-limited resolution is attained using quadratically fewer channels, thereby reducing the measurement complexity while preserving the quantum optimality. Universal quantum circuits based on Gouy phase interferometry are introduced to facilitate this degenerate projection. By employing fractional Fourier transform in a multipath interferometer, optical modes with distinct Gouy phases can be efficiently deviated, approaching the optimal resolution over longer distances. This scheme streamlines the implementation of quantum optimal measurement, offering a practical pathway for superresolution imaging across diverse applications.