  Photodetectors based on nano-structured superconducting thin films are
currently some of the most sensitive quantum sensors and are key enabling
technologies in such broad areas as quantum information, quantum computation
and radio-astronomy. However, their broader use is held back by the low
operation temperatures which require expensive cryostats. Here, we demonstrate
a nitrogen cooled superconducting transition edge sensor, which shows orders of
magnitude improved performance characteristics of any superconducting detector
operated above 77K, with a responsivity of 9.61x10^4 V/W, noise equivalent
power of 15.9 fW/Hz-1/2 and operation speeds up to GHz frequencies. It is based
on van der Waals heterostructures of the high temperature superconductor
Bi2Sr2CaCu2O8, which are shaped into nano-wires with ultra-small form factor.
To highlight the versatility of the detector we demonstrate its fabrication and
operation on a telecom grade SiN waveguide chip. Our detector significantly
relaxes the demands of practical applications of superconducting detectors and
displays its huge potential for photonics based quantum applications.
