Preparation and characterisation of high-dimensional frequency-orbital angular momentum entangled states

Frequency-orbital angular momentum entanglement constitutes a significant resource in quantum information science. This work proposes a novel methodology for preparing and characterizing such entangled states. We demonstrate the preparation and characterization of high-dimensional frequency-orbital angular momentum entangled states, achieving dimensions up to 15. This method features adjustable frequency intervals and flexible encoding schemes, and readily lends itself to further dimensionality enhancement. Furthermore, the characterization technique utilizing the second harmonic generation process can be readily extended to arbitrary high-dimensional frequency state measurements. The novel approach presented here holds profound implications for both quantum information processing and fundamental physics research.