A subwavelength atomic array switched by a single Rydberg atom

Ordered arrays of emitters with subwavelength spacing have emerged as a novel and versatile platform to realize efficient light-matter interfaces.

The strong coupling down to the level of single photons is rooted in the cooperative optical response of the entire array.

In our experiment, we realize such an ordered atomic array by preparing a near-unity filled Mott insulator in an optical lattice deep in the atomic limit.

We confirm the cooperative nature of the array by probing the subradiant optical response both in reflection and transmission of a weak laser beam.

Employing strong dipolar Rydberg interactions, we subsequently controllably switch the optical properties of the entire array with a locally addressed single ancilla atom.

Driving coherent Rabi oscillations on the ancilla, we find evidence that the mirror can be brought in a superposition between transmission and reflection before probing.

Furthermore, we observe indications for dipolar hopping as a potential limit to the performance of the switch, and use spatial shape control to overcome this problem.

Our results pave the way towards the realization of novel quantum metasurfaces and the creation of controlled atom-photon entanglement.