Measurements of cesium PJ-series quantum defect with the microwave spectroscopy.

High-precision microwave spectroscopy has been used to measure the transition frequency of nS → nP (n is the principle quantum number) and further the quantum defect of nP states in a standard cesium magneto-optical trap. A microwave field with 30-μs duration coupling the nS → nP transition yields a narrow linewidth microwave spectroscopy with the linewidth approaching the Fourier limit. After carefully compensating the stray electric and magnetic field and using the diluted atomic gas, we extract improved quantum defects of nP state, δ(nP) = 3.

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.

Dissociation of ultracold cesium Rydberg-ground molecules.

We report the experimental measurements of the decay rate of polar cesium nD5/2 - 6S1/2 Rydberg-ground molecules with a large principal quantum number range of 35 ≤ n ≤ 40. Rydberg molecules are prepared employing the method of two-photon photoassociation and the molecular (atomic) ions, due to autoionization (blackbody photoionization), are detected with a microchannel plate detector. The decay rate Γ of the vibrational ground state of the deep and shadow bound molecules for triplet (TΣ) and mixed singlet-triplet (S,TΣ) are measured by fitting the molecular population with the exponential function.

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.

Autler-Townes splitting of three-photon excitation of cesium cold Rydberg gases.

We demonstrate the three-photon Autler-Townes (AT) spectroscopy in a cold cesium Rydberg four-level atom by detecting the field ionized Rydberg population. The ground state |6S〉, two intermediate states |6P〉 and |7S〉 and Rydberg state |60P〉 form a cascade four-level atomic system. The three-photon AT spectra and AT splittings are characterized by the Rabi frequency Ω and Ω and detuning δ of the coupling lasers.

Rydberg atom-based AM receiver with a weak continuous frequency carrier.

We demonstrate an atom-based amplitude-modulation (AM) receiver for digital communication with a weak continuous frequency carrier using a Rydberg AC Stark effect in a vapor cell and achieve the operating carrier frequency continuously from 0.1 GHz to 5 GHz at a single Rydberg state. A strong local oscillator (LO) field E acts as a gain to shift the Rydberg level to a high sensitivity region, and a weak carrier field E keeps the same frequency with the LO field.

Observation of photoassociation spectroscopy of ultralong 37D + 6SCs Rydberg molecules.

We present an experimental observation of 37D + 6SCs Rydberg-ground molecules by employing a two-photon photoassociation method. Two distinct Rydberg-ground molecular signals, deep and shallow bound molecules, are observed at the red detuning of atomic line. In theory, the model of scattering interaction between the Rydberg electron and ground-state atom is used to simulate the experiments.