Bulletin of the American Physical Society
49th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 63, Number 5
Monday–Friday, May 28–June 1 2018; Ft. Lauderdale, Florida
Session V04: Cold Rydberg Gases and Plasmas |
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Chair: Clayton Simien, U. Alabama, Birmingham Room: Grand C |
Friday, June 1, 2018 10:30AM - 10:42AM |
V04.00001: Enhanced ground-Rydberg coherence times in a state-insensitive optical lattice Jacob Lampen, Huy Nguyen, Matthew Winchester, Lin Li, Paul Berman, Alex Kuzmich By confining Rb atoms in a state-insensitive optical lattice, the lifetime of the 5s-ns coherence is increased to $\sim 20$ $\mu$s, an order of magnitude improvement on prior demonstrations using untrapped atoms. The enhanced lifetimes open new opportunities for high-resolution spectroscopy and quantum information science. As the first demonstration of their utility, the magic values for lattice frequencies are measured and used to extract the 6p-ns reduced electric dipole matrix elements. Good agreement is found with values obtained by numerical integration for an effective one-electron potential for principal quantum numbers n between 30 and 65. [Preview Abstract] |
Friday, June 1, 2018 10:42AM - 10:54AM |
V04.00002: Effects of Fermi Statistics on Trimer Formation in Ultralong-Range Rydberg Molecules J D Whalen, R Ding, S K Kanungo, F B Dunning, T C Killian Excitation of a Rydberg atom in a cold, dense gas leads to the creation of bound states known as ultralong-range Rydberg molecules comprising one, two, or more bound ground-state atoms. The molecular potential formed by the scattering of the Rydberg electron from nearby ground-state atoms. The excitation probability of a Rydberg molecular state depends on the electronic state ($n$, $\ell$) and the degree of spatial correlation between background ground-state atoms. The anti-correlated nature of a gas of spin-polarized fermions reduces the probability for finding two particles separated by less than their thermal de Broglie wavelength, which leads to changes in the molecular formation rate. We present molecular spectra for spin-polarized and unpolarized samples of fermionic $^{87}$Sr (F=9/2), which highlight the effects of particle statistics on molecule formation. [Preview Abstract] |
Friday, June 1, 2018 10:54AM - 11:06AM |
V04.00003: Spectroscopy of \textsuperscript{87}\text{Sr} triplet Rydberg states Roger Ding, Joseph Whalen, Soumya Kanungo, Shuhei Yoshida, Joachim Burgdörfer, Thomas Killian, F. Barry Dunning Quantum statistics play an important role in defining the properties of ultracold gases with strontium being particularly attractive as it posses both bosonic (\textsuperscript{84, 86, 88}\text{Sr} with $I = 0$) and fermionic (\textsuperscript{87}\text{Sr} with $I = 9/2$) isotopes. These effects can be probed with Rydberg states which offer a tunable length scale defined by the size of the Rydberg atom. Crucial to studies involving \textsuperscript{87}\text{Sr} is the ability to excite to well-defined Rydberg states which requires a detailed understanding of the excitation spectrum. In \textsuperscript{87}\text{Sr}, the spectrum is complicated by the presence of strong hyperfine interactions, resulting in a complex series of lines that is challenging to interpret. We present a combined experimental and theoretical characterization of the $\textsuperscript{3}\text{S}\textsubscript{}$ and $\textsuperscript{3}\text{D}\textsubscript{}$ Rydberg series of \textsuperscript{87}\text{Sr} in the range $n \sim 38-99$. [Preview Abstract] |
Friday, June 1, 2018 11:06AM - 11:18AM |
V04.00004: Ion friction in dual species ultracold plasma expansion Tucker Sprenkle, Ross Spencer, Scott Bergeson We create a dual-species ultracold neutral plasma (UNP) by photo-ionizing Yb and Ca atoms in a dual-species magneto-optical trap. Unlike single-species UNP expansion, these plasmas are well outside of the collisionless (Vlasov) approximation. We observe the mutual interaction of the Yb and Ca ions by measuring the rms expansion velocity for each ion species separately. We model the expansion using a fluid code including ion-ion friction. [Preview Abstract] |
Friday, June 1, 2018 11:18AM - 11:30AM |
V04.00005: Impact of Hydrodynamic Expansion on Laser Cooling of an Ultracold Neutral Plasma Thomas Langin, Grant Gorman, Thomas Killian High temperatures and various heat sources make laser-cooling of typical neutral plasmas impractical. However, ultracold neutral plasmas (UNPs), created by photoionizing an ultracold neutral gas, have typical ion temperatures of $\sim 1$K and minimal heating sources, making them amenable to laser cooling. Using a UNP of $^{88}$Sr$^{+}$ we have demonstrated the first application of laser cooling in a neutral plasma. After photoionization, UNPs expand hydrodynamically into vacuum over a time $\tau_{exp}\sim100\mu$s, resulting in the development of an ion expansion velocity field increasing with both time and distance from the plasma center, with typical average terminal expansion velocity of $v_{E}\sim40$m/s. The expansion creates an environment that differs significantly from other systems that have been laser cooled. For example, the Doppler shift resulting from the high value of $v_{T}$ can limit laser cooling to the central region of the plasma, where expansion velocity is minimal. The expansion dynamics depend primarily on the initial plasma size and the detuning of the cooling laser; for judicious choices of these parameters, the plasma expansion can be nearly halted by laser cooling forces, opening new possibilities of neutral plasma confinement and manipulation. [Preview Abstract] |
Friday, June 1, 2018 11:30AM - 11:42AM |
V04.00006: Demonstration of an on-demand single-photon source based on Rydberg blockade in a thermal vapor cell Fabian Ripka, Florian Christaller, Annika Belz, Hao Zhang, Harald Kuebler, Robert Loew, Tilman Pfau Photonic quantum devices based on atomic vapors at room temperature are intrinsically reproducible as well as scalable and integrable. Besides quantum memories for single photons one key device in the field of quantum information processing are on-demand single-photon sources. A promising candidate for realization relies on the combination of four-wave mixing and the Rydberg blockade effect, as was demonstrated for ultracold atoms [1]. Coherent dynamics to Rydberg states [2] have already been demonstrated in thermal vapors, as well as sufficient Rydberg interaction strengths [3] and lifetimes of the collective Rydberg excitations [4]. Here we report on a significant decrease of photon coincidences for photons at 780 nm when the size of the atomic ensemble is reduced to ~ 1 µm i.e. below the Rydberg blockade radius. The normalized photon pair correlation shows a clear signature for anti-bunched photon statistics and a strong evidence for the observation of a cooperative quantum effect in a thermal atomic ensemble. Future directions beyond this proof of principle will be discussed. [1] Dudin et al., Science 336, 6083 (2012) [2] Huber et al., PRL 107, 243001 (2011) [3] Baluktsian et al., PRL 110, 123001 (2013) [4] Ripka et al., Phys. Rev. A, 053429 (2016) [Preview Abstract] |
Friday, June 1, 2018 11:42AM - 11:54AM |
V04.00007: Charged impurities immersed in a Bose-Einstein condensate Florian Meinert, Kathrin Kleinbach, Felix Engel, Thomas Dieterle, Robert Loew, Tilman Pfau Giant Rydberg atoms immersed in a Bose-Einstein condensate provide an exquisite platform to study the interaction of charged impurities with neutral atoms at ultralow temperatures. Typically, the low-energy scattering of the Rydberg electron with neutral perturber atoms residing within the Rydberg orbit constitutes the dominant interaction process, which manifests in density-dependent spectral line shifts and broadening of the Rydberg excitation. Using a tightly focused optical tweezer we access a previously unexplored parameter regime for which the Rydberg electron orbit largely exceeds the spatial extent of the condensate. This reduces the contribution of electron-neutral interaction with increasing principal quantum number in the observed excitation spectrum. Consequently, the interaction of the condensate atoms with the Rydberg ionic core is expected to actively shape the spectral response. I will report on our endeavor to explore this appealing route to study atom-ion interaction in a Bose-Einstein condensate. [Preview Abstract] |
Friday, June 1, 2018 11:54AM - 12:06PM |
V04.00008: Quantum-optical spectroscopy for plasma electric field measurements and diagnostics David Anderson, Georg Raithel, Matthew Simons, Christopher Holloway Measurements of plasma electric fields are essential to the advancement of plasma science and applications. Methods for non-invasive in situ measurements of plasma fields on sub-millimeter length scales with high sensitivity over a large field range remain an outstanding challenge. Here, we introduce and demonstrate a method for plasma electric field measurements and diagnostics that employs electromagnetically induced transparency as a high-resolution quantum-optical probe for the Stark energy level shifts of plasma-embedded Rydberg atoms, which serve as highly-sensitive field sensors with a large dynamic range. The method is applied in diagnostics of plasmas photo-excited out of a cesium vapor. The plasma electric fields are extracted from spatially-resolved measurements of field-induced shape changes and shifts of Rydberg resonances in rubidium tracer atoms. Measurement capabilities over a range of plasma densities and temperatures are exploited to characterize plasmas in applied magnetic fields and to image electric-field distributions in cyclotron-heated plasmas. [Preview Abstract] |
Friday, June 1, 2018 12:06PM - 12:18PM |
V04.00009: Theory of long range interactions for Rydberg states attached to hyperfine split cores Francis Robicheaux, Donald Booth, Mark Saffman Theory for one and two atom interactions is developed for the case when the atoms have a Rydberg electron attached to a hyperfine split core state, a situation relevant for some rare earth and some alkaline earth atoms proposed for experiments on Rydberg-Rydberg interactions. For the rare earth atoms, the core electrons can have a very substantial total angular momentum, $J$, and a non-zero nuclear spin, $I$. For alkaline earth atoms there is a single, $s$, core electron whose spin can couple to a non-zero nuclear spin for odd isotopes. The hyperfine splitting of the core state can lead to substantial mixing between the Rydberg series attached to different thresholds. Compared to the unperturbed Rydberg series of the alkali atoms, series perturbations and near degeneracies from the different parity states could lead to qualitatively different behavior for single atom Rydberg properties (polarizability, Zeeman mixing and splitting, etc) as well as Rydberg-Rydberg interactions (C5 and C6 matrices). [Preview Abstract] |
Friday, June 1, 2018 12:18PM - 12:30PM |
V04.00010: Cs $62D_J$ Rydberg-atom macrodimers formed by long-range multipole interaction Jianming Zhao, Georg Raithel We report on long-range macrodimers formed by $D$-state cesium Rydberg atoms. Cesium $[62D_{J}]_2$ 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 macrodimers below the $[62D_{J}]_2$ asymptotes. The 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. Initial lifetime estimates are presented. [Preview Abstract] |
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