In case of electromagnetic fields i think it is like this: A electromagnetic wave is caused by an accelerating charge, this causes a temporal change in the electric and magnetic field around it which propagates through space at the velocity of light. If we have a transmitter and multiple receiving antennas at equal distances from the transmitter, the enery needed to accelerate the charge will be distributed and each receiver will pickup an equal amount of this energy to accelerate the electrons in the receiving antennas. What happens if we only add enough energy to emit a single photon. Since the photon comes only in lumps, there is a chance that only one of the receivers will pickup this photon? and on average if we emit enough photons, each receiver will pickup equal amounts? Now how does this work if we accelerate a mass in stead of a charge ? Other then for charge, the mass affects its surrounding space, by defining the unit metric in each point of the space (unit time, unit distances). Hence when accelerating the mass, a spherical wave will run through space causing a temporal change of the metric in each point. If we no add just enough energy to emit just a single graviton, what happens ? If we have receivers at equal distances, will there be a chance that only in one of them the metric varies, or will the metric still vary in each point on the surface of the sphere of the gravitational wave? 2nd will the change in the metric come in quanta, meaning , will the change in the metric (unit distance at this point) come in lumps?