  Quantum-enhanced sensing has a goal of enhancing a parameter sensitivity with
input quantum states, while quantum illumination has a goal of enhancing a
target detection capability with input entangled states in a heavy noise
environment. Here we propose a concatenation between quantum-enhanced sensing
and quantum illumination that can take quantum advantage over the classical
limit. First, phase sensing in an interferometry is connected to a target
sensing via quantum Fisher information. Second, the target sensitivity is
investigated in noisy quantum-enhanced sensing. Under the same input state
energy, for example, N-photon entangled states can exhibit better performance
than a two-mode squeezed vacuum state and a separable coherent state.
Incorporating a photon-number difference measurement, finally, the noisy target
sensitivity is connected to a signal-to-noise ratio which is associated with a
minimum error probability of discriminating the presence and absence of the
target. We show that both the target sensitivity and the signal-to-noise ratio
can be enhanced with increasing thermal noise.
