Recently I occasionally read about "quantum radar" and "quantum illumination", I never heard about before.

As I see it, people there say they can send a single photon and use quantum entanglement somehow to distinguish their photon from noise photons. How does it actually work? They say the entaglement gives the gain which is "exponential on the number of qubits". But how they put more than a single qubit into a photon? If they spread it into a sequence of photons, then the probability to catch all of them in the same order and without noise photons interfering in between is also exponentially low, right? So? How does it work?

Is my understanding of quantum illumination as an ability to distinguish photons right?

What scientific applications can it give? Can it allow us study more about light-media interaction, like some nonlinear or multiphoton effects?

Can it give as a sort of telephatic communication across the Earth, if we use 8 Hz spherical resonances? The bandwidth is scarce, but the ability to distinguish photons neglects it, allowing to send a lot of streams concurrently, besides, low frequency means we can send loads of photons in an entangled sequence without using much energy. This low frequency spreads everywhere, including underwater, etc., low frequencies are already used to communiate with submarines.