Addressing two-level systems variably coupled to an oscillating field

We propose a simple method to spectrally resolve an array of identical two-level systems coupled to an inhomogeneous oscillating field. The addressing protocol uses a dressing field with a spatially dependent coupling to the atoms. We validate this scheme experimentally by realizing single-spin addressing of a linear chain of trapped ions that are separated by ∼3 μm, dressed by a laser field that is resonant with the micromotion sideband of a narrow optical transition.