  In a recent work we showed that the detection of the exchange of a single
graviton between a massive quantum resonator and a gravitational wave can be
achieved. Key to this ability are the experimental progress in preparing and
measuring massive resonators in the quantum regime, and the correlation with
independent LIGO detections of gravitational waves that induce stimulated
absorption. But do stimulated single-graviton processes imply the quantization
of gravity? Here we analyze this question and make a historic analogy to the
early days of quantum theory. We discuss in what ways such experiments can
indeed probe key features of the quantized interaction between gravity and
matter, and outline five experimental tests. This capability would open the
first window into experimental exploration of quantum gravity.
