Why does the read-out efficiency increase when coupling an atomic ensemble to an optical cavity?

Question

I went through a paper where it mentioned that the read-out efficiency of a quantum memory would be increased by coupling the atomic ensemble with an optical cavity.
I think rydberg atoms were used to make the atomic ensemble, and the rydberg blockade effect was used.

Can anybody explain to me, how the read-out efficiency increases?

The DOI of the paper is: 10.1109/PHOSST.2017.8012667