Rydberg atom-based radio frequency sensors are self-calibrated in the sense that the radio frequency field is determined by measuring it against the structure of the atom, since Planck’s constant has a fixed value. To increase the accuracy of Rydberg atom-based radio frequency sensors, it is important to improve our knowledge of the atomic structure of cesium. Namely, we are focused on precision spectroscopy of the Rydberg levels of cesium to further improve the accuracy of the transition dipole moments between cesium Rydberg states. Interestingly, these measurements can also have a bearing on using atoms for sensitive tests of quantum electrodynamics and physics beyond the standard model. The work has a rare combination of application and curiosity driven motivations.

Line chart showing the accurate and narrow Rydberg lineshape observed.
Fig. 1: An example of the narrow Rydberg lineshapes observed in our measurements. These lineshapes, along with tight control of low-frequency electric and magnetic fields, allows us to obtain absolute line position accuracies below 1 kHz.
Infrared photo depicting cesium device, which appears green.
Fig. 2: The cesium magneto-optical trap used for the measurements, pictured on an infrared camera.

With modern technological developments, it is now possible to make atomic structure measurements with unprecedented accuracy and precision. The development of laser cooling and trapping for Doppler free spectroscopy and frequency combs for absolute frequency measurement are tools that did not exist until quite recently, but enable measurements of atomic structure that can go significantly beyond what was feasible in the past. Absolute accuracies below 1 kHz are possible.

In our lab, we use a magneto-optical trap (pictured in Fig. 2) to cool and capture cesium atoms. We excite the cesium atoms to Rydberg states in an environment free of low frequency electric and magnetic fields. We detect the Rydberg atoms using time-of-flight spectroscopy by ionizing them and projecting them onto a charge sensitive detector, one at a time. The excitation lasers are locked to a frequency comb. The frequency comb allows us to determine the frequency of the lasers to very high precision. The experimental setup allows us to measure Rydberg levels with very small absolute error, referenced to the ground state of the cesium atom.

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Interested in Collaborating or Joining Our Team?

If you are interested in collaborating with us or becoming a technical staff member, including student internships and postdoctoral training, please contact James Shaffer at [email protected].