  The Gertsenshtein effect could in principle be used to detect a single
graviton by firing it through a region filled with a constant magnetic field
that enables its conversion to a photon, which can be efficiently detected via
standard techniques. The quantization of the gravitational field could then be
inferred indirectly. We show that for currently available single-photon
detector technology, the Gertsenshtein detector is generically inefficient,
meaning that the probability of detection is $\ll 1$. The Gertsenshtein
detector can become efficient on astrophysical scales for futuristic
single-photon detectors sensitive to frequencies in the Hz to kHz range. It is
not clear whether such devices are in principle possible.
