Increasing two-photon entangled dimensions by shaping input-beam profiles
Shi-Long Liu, Yingwen Zhang, Chen Yang, Shi-Kai Liu, Zheng Ge, Yin‐Hai Li, Yan Li, Zhi‐Yuan Zhou, Guang‐Can Guo, Bao-Sen Shi
Abstract
Photon pairs entangled in high-dimensional orbital angular momentum (OAM) degrees of freedom (DOF) have been widely regarded as a possible source for improving the capacity of quantum information processing. The generation of a high-dimensional maximally entangled state in the OAM DOF is therefore much desired. In this work, we demonstrate a simple method to generate a broader and flatter OAM spectrum, i.e., a larger spiral bandwidth (SB), of entangled photon pairs generated through spontaneous parametric down-conversion by modifying the pump beam profile. By investigating both experimentally and theoretically, we find that an exponential pump profile that is roughly the inverse of the mode profiles of the single-mode fibers used for OAM detection will provide a much larger SB compared to a Gaussian-shaped pump.