Three‐Photon High‐Order Orbital Angular Momentum NOON States for Sub‐Shot‐Noise Angular Measurement

The quantum measurement scheme exhibits significant advantages in precision measurement, due to super‐sensitivity. In particular, the multi‐photon NOON states realized via path or polarization degrees of freedom have been successfully validated in various phase measurement experiments. Orbital angular momentum (OAM), another important photonic degree of freedom, has also shown great potential for angular measurement. Combining the NOON state with OAM is expected to demonstrate quantum advantages in such measurements. Here we experimentally generate a three‐photon NOON state based on OAM for the first time, and apply it to super‐sensitive angular measurement. By utilizing a NOON state with a topological charge as high as , we have achieved a precision beyond the standard quantum limit. Through the reduction of angle uncertainty, a sensitivity reaching approximately 82% of the ideal Heisenberg limit is achieved. These results establish the practical utility of OAM‐enhanced NOON states in advancing angular metrology. Our experiments indicate that increasing either the topological charge or the photon number can substantially improve angular measurement accuracy. Importantly, the proposed scheme exhibits excellent scalability in key parameters, underscoring its potential for high‐precision angle‐sensing applications.