Microwave coupled Zeeman splitting spectroscopy of a cesium nP Rydberg atom.

We perform measurements of microwave spectra of cesium Rydberg 51S → 51P transitions with the linewidth approaching the Fourier limit. A two-photon scheme excites the ground-state atoms to the Rydberg 51S state, and a weak microwave photon couples the Rydberg transition of 51S → 51P. The hyperfine structure of 51P can be clearly resolved with a narrow linewidth microwave spectra by using the method of ion detection.

Robust Ramsey interferometer based on a single Rydberg polariton.

We demonstrate a robust single-photon Ramsey interferometer based on a single Rydberg excitation, where the photon is stored as a Rydberg polariton in an ensemble of atoms. This coherent conversion of the photon to Rydberg polariton enables to split an incoming photon into a superposition state of two Rydberg states by applying microwave fields, which constructs two paths of interferometer. Ramsey interference fringes are demonstrated when we scan either the detuning of the microwave or the free evolution time, from which we can obtain the resonant transition frequency of two Rydberg states.

Manipulation of single stored-photon with microwave field based on Rydberg polariton.

We demonstrate a coherent microwave manipulation of a single optical photon based on a single Rydberg excitation in an atomic ensemble. Due to the strong nonlinearities in a Rydberg blockade region, a single photon can be stored in the formation of Rydberg polariton using electromagnetically induced transparency (EIT). The manipulation of the stored single photon is performed by applying a microwave field that resonantly couples the nS and nP, while the coherent readout is performed by mapping the excitation into a single photon.

Dephasing of ultracold cesium 80D-Rydberg electromagnetically induced transparency.

We study Rydberg electromagnetically induced transparency (EIT) of a cascade three-level atom involving 80D state in a strong interaction regime employing a cesium ultracold cloud. In our experiment, a strong coupling laser couples 6P to 80D transition, while a weak probe, driving 6S to 6P transition, probes the coupling induced EIT signal. At the two-photon resonance, we observe that the EIT transmission decreases slowly with time, which is a signature of interaction induced metastability.