A Single Atom Scanning Microscope for Cavity Field Detection*

We present a novel cavity QED system of a tweezer array of single rubidium atoms trapped in a high finesse near-concentric optical cavity. Individual atom-cavity couplings are controlled by tuning tweezer position, and single atoms are imaged with high fidelity through a high numerical aperture (NA=0.5) objective transverse to the cavity.

In this work, we use a pair of optical molasses beam to illuminate and cool atoms at the same time, reaching minute-scale atom lifetime in tweezers convenient for multi-frame fluoresecent imaging sequence. Overlaying the atom tweezer array with cavity modes of different wavelengths (780 and 1560nm) and spatial structure (TEM₀₀ and TEM₀₁ Hermite-Gaussian modes), we can scan the cavity field at high resolution by detecting the AC Stark shift they impose on the atoms, manifested in the fluorescence imaging photon scattering rate. By Stepping the optical molasses frequency in the multi-frame sequence, this single atom microscopy maps out the brightness-frequency response curve that is analogous to the force curve in AFM, which provides a low noise, detailed characterization of the spatial structure of the cavity modes.

With a complete characterization of the bichromatic cavity fields, we hope to use our aparatus' cavity readout ability for quantum feedback and single atom addressing ability for correlation study of few- to many-body states.