High-fidelity, low-latency polarization quantum state transmissions over a hollow-core conjoined-tube fiber at around 800 nm

Hollow-core fiber (HCF) promises to unify air-borne light propagation and non-line-of-sight transmission, thus holding great potential for versatile photonics-based quantum information applications. The early version of HCF based on photonic-bandgap guidance has not proven itself a reliable quantum channel because of the poor modal purity in both spatial and polarization domains, as well as significant difficulty in fabrication when the wavelength shifts to the visible region. In this work, based on the polarization degree of freedom, we demonstrate high-fidelity (similar to 0.98) single-photon transmission and distribution of entangled photons over a 36.4 m hollow-core conjoined-tube fiber (CTF) by using commercial silicon single-photon avalanche photodiodes. Our CTF realizes the combined merits of low loss, high spatial modal purity, low polarization degradation, and low chromatic dispersion. We also demonstrate single-photon low-latency (similar to 99.96% speed of light in vacuum) transmission, paving the way for extensive uses of HCF links in versatile photonics-based quantum information processing. (C) 2021 Chinese Laser Press