simple target-detection scheme, first proposed by Lloyd for photonic qubits [@Lloyd1463]. It harnesses entanglement in a quantum state of light to better infer the presence or absence of a weakly reflecting object flooded by white noise. The protocol distinguished itself in displaying quantum advantage, even in regimes so noisy that no entanglement survives. It presented a remarkable deviation from the conventional view that quantum technologies are fragile, displaying advantage only in carefully engineered environments which ensure little or no loss of entanglement. Since its original inception, quantum illumination has gained significant scientific interest. Many variants have been proposed, including some that make use of Gaussian states in the continuous-variable regime [@PhysRevLett.101.253601; @SHGSC16; @PhysRevA.80.052310] and inspiring a number of different experimental realizations [@PhysRevLett.110.153603; @PhysRevLett.111.010501; @PhysRevLett.114.110506; @PhysRevLett.114.080503]. The phenomenon has also seen applications outside metrology, where quantum illumination has been harnessed to provide security against passive eavesdropping in the setting of secure communication [@PhysRevA.80.022320].

Quantum illumination challenges the conventional view that entanglement alone can explain all quantum advantage. It joins a particularly surprising class of protocols that appear to thrive in noisy, possibly entanglement-breaking environments [@PhysRevLett.81.5672; @PhysRevLett.101.200501]. What other quantum resources, then, could help us better understand its noisy resilience? Quantum discord 