  Detecting light at the single-photon level is one of the pillars of emergent
photonic technologies. This is realized through state-of-the-art
superconducting detectors that offer efficient, broadband and fast response.
However, the use of superconducting thin films with low TC limits their
operation temperature below 4K. In this work, we demonstrate proof-of-concept
nanodetectors based on exfoliated, two-dimensional cuprate superconductor
Bi2Sr2CaCu2O8-{\delta} (BSCCO) that exhibit single-photon sensitivity at
telecom wavelength at a record temperature of T = 20K. These non-optimized
devices exhibit a slow (ms) reset time and a low detection efficiency
(10^(-4)). We realize the elusive prospect of single-photon sensitivity on a
high-TC nanodetector thanks to a novel approach, combining van der Waals
fabrication techniques and a non-invasive nanopatterning based on light ion
irradiation. This result paves the way for broader application of single-photon
technologies, relaxing the cryogenic constraints for single-photon detection at
telecom wavelength.
