The radar cross section σC is an objective measure of the "radar visibility" of an object. As such, σC is an important concept for the correct characterization of the operational performance of radar systems. Furthermore,
σC is equally essential for the design and development of stealth weapon systems and platforms. Recent years
have seen the theoretical development of quantum radars, that is, radars that operate with a small number
of photons. In this regime, the radar-target interaction is described through photon-atom scattering processes
governed by the laws of quantum electrodynamics. As such, it is theoretically inconsistent to use the same σC
to characterize the performance of a quantum radar. In this paper we define a quantum radar cross section σQ
based on quantum electrodynamics and interferometric considerations. We discuss the theoretical challenges of
defining σQ, as well as computer simulations of σC and σQ for simple targets.