Generating heralded single photons with a switchable orbital angular momentum mode

The orbital angular momentum (OAM) carried by photons defines an infinitely dimensional discrete Hilbert space. With OAM modes, high-dimensional quantum states can be achieved for quantum communication and cryptography. Here we demonstrate a heralded single-photon source with a switchable OAM mode, which consists of a heralded single-photon source and an integrated OAM emitter as the mode converter. As the first step, the heralded single-photon source is based on the dispersion-shifted fiber. In this work, the OAM mode (quantized by topological charge l) carried by the heralded single photon (at fixed wavelength of 1555.75 nm) can be switched within the range of l=3–7 while the mode purity is more than 80%.