$PT$-symmetry in Rydberg atoms

We propose a scheme to realize parity-time ($PT$)-symmetry in an ensemble of strongly interacting Rydberg atoms, which act as superatoms due to the dipole blockade mechanism. We show that Rydberg-dressed ⁸⁷Rb atoms in a four-level inverted Y-type configuration is highly efficient to generate the refractive index for a probe field, with a symmetric (antisymmetric) profile spatially in the corresponding real (imaginary) part. Comparing with earlier investigations, the present scheme provides a versatile platform to control the system from $PT$-symmetry to non-$PT$-symmetry via different external parameters, i.e., coupling field detuning, probe field intensity and control field intensity. (letter)