mean number of noise photons arriving at the detector is the same as when the object is absent. This approach has been adopted by [@PhysRevLett.101.253601] to avoid a “shadowing effect”—so that the object is not detected by a reduction in the number of noise photons arriving at the detector. The typical illumination scenario that has greatest quantum advantage is for the regime of low object reflectivity and high noise, i.e., $\epsilon\ll 1$ and $\bar n \ll \bar n_{\rm env}$, where $\bar n$ is the mean photon number of the probe. We term this as the intense white-noise limit.

Consider Figs. \[fig\_swapdiagram\](c) and \[fig\_swapdiagram\](d). After the noise injection, the entanglement is reduced or lost all together, before any information is encoded within the probe. In fact, for all the settings studied in Sec. \[sec\_results\], the entanglement after noise injection is strictly zero. Nevertheless we see a quantum advantage. Thus, quantum entanglement itself does not give a complete picture on why illumination thrives in such noise. Our goal here is to see if discord will give us additional insight.

In the next section, we will use the communication formalism to study the amount of information that Alice can communicate to Bob under 