Ultrathin optical quantum CNOT gate based on a single-layer metasurface

Compact controlled-NOT (CNOT) gates are essential for achieving large-scale quantum information processing. Recently, metasurfaces have been emerging as a promising miniaturized platform for quantum optics thanks to their advanced light field manipulation capability and subwavelength thickness. Here we report, for the first time, to our knowledge, the experimental demonstration of a quantum CNOT gate realized with a single-layer Pancharatnam–Berry phase-based dielectric metasurface. The metasurface completes the functions of three beam splitters, reducing the thickness of the logic gate to the subwavelength scale. The truth table fidelity reaches as high as 94.7% and state fidelities of the generated maximally entangled Bell states exceed 80%. This provides an ultrathin device for quantum information processing and holds promise for advancing quantum technology.