Cavity quantum electrodynamics in a high numerical aperture resonator

From fundamental studies of light-matter interaction to applications in quantum networking and sensing, cavity quantum electrodynamics (QED) provides a toolbox to control interactions between atoms and photons. The coherence of interactions is determined by the single-pass atomic absorption and the number of photon round-trips. Reducing the cavity loss has enabled resonators supporting~1-million roundtrips, but with limited material choices and increased alignment sensitivity. Here we present a high numerical-aperture,lens-based resonator that pushes the single-atom-single-photon absorption probability near its fundamental limit by reducing the mode size at the atom to order lambda. This resonator provides a single-atom cooperativity of 1.6 in a cavity where the light circulates only~10times. We load a single 87Rb atom into this cavity, observe strong coupling, and demonstrate cavity-enhanced detection with fidelity of 99.55(6)% and survival of 99.89(4)% in 130 microseconds. Introducing..., This data was collected using a single photon counter and processed using Jupyter Notebook (python), , # Cavity quantum electrodynamics in a high numerical aperture resonator

[https://doi.org/10.5061/dryad.xgxd254s8](https://doi.org/10.5061/dryad.xgxd254s8)

## Description of the data and file structure

Data was taken on the Small Waist apparatus in the Simon Lab at Stanford university. 

### Files and variables

#### File: DATA\_afm\_waist\_scan.csv

**Description:** 2D heat map of afm cavity waist scan

##### Variables:

* x, measured in units of microns. A scan of the afm tip to measure the waist in x
* y, measured in units of microns. A scan of the afm tip to measure the waist in y

#### File: DATA\_cavity\_spectrum.csv

##### Variables

* Mirror Displacement (microns): translating the cavity length allows one to scan through resonances
* Transmission (arbitrary units): the amount of light circulating in the cavity varies as we sweep through the resonances

#### File: DATA\_fidelity\_counts.csv

**Description:** histogram counts, 1 ms bin size

##### Variables

* Cou...