arXiv subjects

Suying Bai

Publications and source records attributed to Suying Bai.

7 recordsLinked to original sources

arXiv2021

Observation of Blackbody Radiation Enhanced Superradiance in ultracold Rydberg Gases

An ensemble of excited atoms can synchronize emission of light collectively in a process known as superradiance when its characteristic size is smaller than the wavelength of emitted photons. The underlying superradiance depends strongly on electromagnetic (photon) fields surrounding the atomic ensemble. High mode densities of microwave photons from $300\,$K blackbody radiation (BBR) significantly enhance decay rates of Rydberg states to neighbouring states, enabling superradiance that is not possible with bare vacuum induced spontaneous decay. Here we report observations of the superradiance of ultracold Rydberg atoms embedded in a bath of room-temperature photons. The temporal evolution of the Rydberg $|nD\rangle$ to $|(n+1)P\rangle$ superradiant decay of Cs atoms ($n$ the principal quantum number) is measured directly in free space. Theoretical simulations confirm the BBR enhanced superradiance in large Rydberg ensembles. We demonstrate that the van der Waals interactions between Rydberg atoms change the superradiant dynamics and modify the scaling of the superradiance. In the presence of static electric fields, we find that the superradiance becomes slow, potentially due to many-body interaction induced dephasing. Our study provides insights into many-body dynamics of interacting atoms coupled to thermal BBR, and might open a route to the design of blackbody thermometry at microwave frequencies via collective, dissipative photon-atom interactions.

physics.atom-ph↗

arXiv2020

Cesium $nD_{J}$+$6S_{1/2}$ Rydberg molecules and their permanent electric dipole moments

Cs$_2$ Rydberg-ground molecules consisting of a Rydberg, $nD_{J}$ (33 $\leq$ $n$ $\leq$ 39), and a ground state atom, 6$S_{1/2} (F=$3 or 4$)$, are investigated by photo-association spectroscopy in a cold atomic gas. We observe vibrational spectra that correspond to triplet $^TΣ$ and mixed $^{S,T}Σ$ molecular states. We establish scaling laws for the energies of the lowest vibrational states vs principal quantum number and obtain zero-energy singlet and triplet $s$-wave scattering lengths from experimental data and a Fermi model. Line broadening in electric fields reveals the permanent molecular electric-dipole moments; measured values agree well with calculations. We discuss the negative polarity of the dipole moments, which differs from previously reported cases.

physics.atm-clus↗

arXiv2019

Observation of many-body dynamics of Rydberg atoms based on antiblockade using two-color excitation

We investigate a long-range interaction between $64D_{5/2}$ Rydberg-atom pairs and antiblockade effect employing a two-color excitation scheme. The first color (pulse A) is set to resonantly excite the Rydberg transition and prepare a few seed atoms, which establish a blockade region due to strong long-range interaction between Rydberg-atom pairs. The second color (pulse B) is blue detuned relative to Rydberg transition and enables further Rydberg excitation of atoms by counteracting the blockade effect. It is found that a few seed atoms lead to a huge difference of the Rydberg excitation with pulse B. The dynamic evolution of antiblockade excitation by varying the pulse-B duration at 30-MHz blue detuning is also investigated. The evolution result reveals that a small amount of seed atoms can trigger an avalanche Rydberg excitation. A modified superatom model is used to simulate the antiblockade effect and relevant dynamic evolution. The simulations are consistent with the experimental measurements.

physics.atom-ph↗

arXiv2018

Adiabatic potentials of cesium $(nD_J)_2$ Rydberg-Rydberg macrodimers

Electrostatic multipole interactions generate long-range Rydberg-Rydberg macrodimer. We calculate the adiabatic potentials of cesium $(nD_{J})_2$ Rydberg macrodimers for principal quantum numbers $n$ ranging from 56 to 62, for $J=3/2$ and $5/2$, and for the allowed values of the conserved sum of the atomic angular-momentum components along the internuclear axis, $M$. For most combinations $(n, M, J)$ exactly one binding potential exists, which should give rise to Rydberg macrodimer states. We study the dependence of the adiabatic potentials on the size of the two-body basis sets used in the calculation, and on the maximal order, $q_{max}$, of the multipole terms included in the calculation. We determine the binding energies and lengths of the binding adiabatic potentials, and investigate their scaling behaviors as a function of the effective principal quantum number; these parameters are relevant to experimental preparation of Rydberg-atom macrodimers. Avoided crossings between adiabatic potentials affect the well shapes and the scaling behaviors differently in two distinct domains in $n$. We discuss an experimental scheme for preparing $(nD_J)_2$ Rydberg-atom macrodimers using two-color double-resonant photoassociation.

physics.atom-ph↗

arXiv2017

Cs nDJ Rydberg-atom macrodimers formed by long-range multipole interaction

Long-range macrodimers formed by D-state cesium Rydberg atoms are studied in experiments and in calculations. Cesium 62DJ-62DJ Rydberg-atom macrodimers, bonded via long-range multipole interaction, are prepared by two-color photo-association in a cesium atom trap. The first color (pulse A) resonantly excites seed Rydberg atoms, while the second (pulse B, detuned by the molecular binding energy) resonantly excites the Rydberg-atom macrodimer states below the 62DJ pair asymptotes. The Rydberg-atom molecules are measured by extraction of auto-ionization products and Rydberg-atom electric-field ionization, and ion detection. Molecular spectra are compared with calculations of adiabatic molecular potentials. The lifetime of the molecules is obtained from exponential fits to the dependence of the molecular signal on the detection delay time; lifetimes of about 6 us are found.

physics.atom-ph↗

arXiv2017

Transition from electromagnetically induced transparency to Autler-Townes splitting in cold cesium atoms

Electromagnetically induced transparency (EIT) and Aulter-Townes splitting (ATS) are two similar yet distinct phenomena that modify the transmission of a weak probe field through an absorption medium in the presence of a coupling field, featured in a variety of three-level atomic systems. In many applications it is important to distinguish EIT from ATS splitting. We present EIT and ATS spectra in a cold-atom three-level cascade system, involving the 35$S_{1/2}$ Rydberg state of cesium. The EIT linewidth, $γ_{EIT}$, defined as the full width at half maximum (FWHM), and the ATS splitting, $γ_{ATS}$, defined as the peak-to-peak distance between AT peak pairs, are used to delineate the EIT and ATS regimes and to characterize the transition between the regimes. In the cold-atom medium, in the weak-coupler (EIT) regime $γ_{EIT}$ $\approx$ A + B($Ω_{c}^2$ + $Ω_{p}^2)/Γ_{eg}$, where $Ω_{c}$ and $Ω_{p}$ are the coupler and probe Rabi frequencies, $Γ_{eg}$ is the spontaneous decay rate of the intermediate 6P$_{3/2}$ level, and parameters $A$ and $B$ that depend on the laser linewidth. We explore the transition into the strong-coupler (ATS) regime, which is characterized by the linear relation $γ_{ATS}$ $\approx$ $Ω_{c}$. The experiments are in agreement with numerical solutions of the Master equation.

physics.atom-ph↗

arXiv2017

Atom-based radio-frequency field calibration and polarization measurement using cesium $nD_J$ Floquet states

We investigate atom-based electric-field calibration and polarization measurement of a 100-MHz linearly polarized radio-frequency (RF) field using cesium Rydberg-atom electromagnetically induced transparency (EIT) in a room-temperature vapor cell. The calibration method is based on matching experimental data with the results of a theoretical Floquet model. The utilized 60$D_J$ fine structure Floquet levels exhibit $J$- and $m_j$-dependent AC Stark shifts and splittings, and develop even-order RF-modulation sidebands. The Floquet map of cesium 60$D_J$ fine structure states exhibits a series of exact crossings between states of different $m_j$, which are not RF-coupled. These exact level crossings are employed to perform a rapid and precise ($\pm 0.5\%$) calibration of the RF electric field. We also map out three series of narrow avoided crossings between fine structure Floquet levels of equal $m_j$ and different $J$, which are weakly coupled by the RF field via a Raman process. The coupling leads to narrow avoided crossings that can also be applied as spectroscopic markers for RF field calibration. We further find that the line-strength ratio of intersecting Floquet levels with different $m_j$ provides a fast and robust measurement of the RF field's polarization.

physics.atom-ph↗