  We analyze in detail the possibility to use charge-dipole interaction between
a single polar molecule or a 1D molecular array and a single Rydberg atom to
read out rotational populations. The change in the Rydberg electron energy is
conditioned on the rotational state of the polar molecules, allowing for
realization of a CNOT quantum gate between the molecules and the atom.
Subsequent readout of the atomic fluorescence results in a non-destructive
measurement of the rotational state. We study the interaction between a 1D
array of polar molecules and an array or a cloud of atoms in a Rydberg
superatom (blockaded) state and calculate the resolved energy shifts of Rb(60s)
with KRb and RbYb molecules, with N=1, 3, 5 molecules. We show that collective
molecular rotational states can be read out using the conditioned Rydberg
energy shifts.
