  The superconducting (SC) state of magic-angle twisted bilayer graphene
(MATBG) shows exceptional properties, as it consists of an unprecedentedly
small electron (hole) ensemble of only ~ 10 power 11 carriers per square
centimeter, which is five orders of magnitude lower than in traditional
superconductors. This results in an ultra-low electronic heat capacity and
kinetic inductance of this truly two-dimensional SC, and provides
record-breaking key parameters for a variety of quantum sensing applications,
in particular in thermal sensing and single photon detection (SPD), which
traditionally exploit thermal effects in nanostructured superconducting thin
films. In this work, we systematically study the interaction of the
superconducting state of MATBG with individual light quanta. We discover full
destruction of the SC state upon absorption of a single infrared photon even in
a 16 square micrometer sized device, which showcases its exceptional bolometric
sensitivity. Upon voltage biasing close to its critical current, we further
show that this non-optimized device can be used as a SPD, whose click-rate is
proportional to the number of absorbed photons, following Poissonian
statistics. Our work offers insights into the MATBG-photon interaction and
shows up pathways to use low-carrier density graphene-based superconductors as
a new platform for developing revolutionary new quantum devices and sensors.
