This invention describes a nanophotonic element that simultaneously performs two distinct polarization-sorting operations. Each photon incident on the device is directed to one of four quadrants in the far field or focal plane and are uniquely encoded based on their polarization outcome in both the linear and circular bases in a single measurement, rather than in sequential basis settings. Background: Polarization-entangled photons are important in quantum information technologies such as secure communications and computing. As these applications rely on genuine quantum correlations, the reliable verification and precise measurement of entanglement are essential. Traditional polarization analyzers and tomography setups rely on bulk optical components like waveplates, polarizers, and beamsplitters. These systems are often hard to scale down, meaning they lack portability and require precise alignment. In contrast, metasurface-based solutions offer compact and robust solutions that overcome speed, size, and scalability limitations of conventional approaches. Applications:
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