Bulletin of the American Physical Society
52nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 66, Number 6
Monday–Friday, May 31–June 4 2021; Virtual; Time Zone: Central Daylight Time, USA
Session Q06: Rydberg Atoms and Cold PlasmasLive
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Chair: Clayton Simien, Alabama-Birmingham |
Thursday, June 3, 2021 8:00AM - 8:12AM Live |
Q06.00001: Ultracold neutral plasma expansion in a strong uniform magnetic field Robert T Sprenkle, Scott D Bergeson The ion temperature in ultracold neutral plasmas is limited by disorder-induced heating (DIH). This process increases the ion temperature from 0.001 K to around 2 K in 100 ns. It occurs because of the sudden appearance of close neighboring ions in an initially uncorrelated state. Previous work in our group has shown that DIH can be mitigated using electron screening. It has been suggested that DIH could be further supressed by introducing a strong, uniform magnetic field. The field will keep the electrons nearer their parent ions, reducing the ion-ion electrical forces in DIH. The field will also prevent the plasma from expanding transverse to the field, additionally influencing the ion temperature. We are building an experiment to study DIH and expansion of an ultracold neutral Ca+ plasma in a field of B = 0.3 T. We will use fluorescence imaging to measure both the time-evolving ion temperature and density. In this talk I will present both experimental design and preliminary expansion data. |
Thursday, June 3, 2021 8:12AM - 8:24AM Live |
Q06.00002: Velocity and Temperature Evolution of Ultracold Neutral Plasmas with Exponentially Decaying Density Distributions MacKenzie Warrens, Grant M Gorman, Stephen Bradshaw, Tom C Killian Ultracold neutral plasmas (UNPs) occupy an exotic low-temperature and low-density regime of plasma physics, and they provide a powerful platform for studying fundamental plasma physics processes such as plasma waves, transport, and expansion into vacuum. Previous UNP experiments have used plasmas with an initial Gaussian density distribution, for which the expansion into vacuum is well understood. Another interesting initial profile is an exponentially decaying density distribution, which is formed by photoionizing atoms in a quadrupole magnetic trap. While exponential plasmas have similar characteristic length and time scales as Gaussian plasmas, and are predominantly in the hydrodynamic regime, the velocity and temperature profiles differ. This talk compares the velocity and temperature evolution of exponential and Gaussian UNPs, and examines the potential for wave breaking and shock waves in exponential UNPs. |
Thursday, June 3, 2021 8:24AM - 8:36AM Live |
Q06.00003: Laser-Induced Fluorescence Imaging of a Magnetically Confined, Spin-Polarized Ultracold Neutral Plasma Grant M Gorman, MacKenzie Warrens, Stephen Bradshaw, Tom C Killian Ultracold neutral plasmas (UCNPs), created by photoionization of a cold gas, are an excellent platform for studying neutral plasmas in far more complex environments such as plasma in the Sun’s atmosphere, white dwarf stars, and inertial-confinement fusion devices. Magnetized UCNPs are of current interest because of the interplay of magnetization and strong coupling, connection to plasma confinement, and modification of recombination dynamics in strong fields. We recently demonstrated the magnetic confinement of UCNPs at the null of a biconic cusp, or quadrupole magnetic field, with confinement times of up to 0.5 ms. Here, we describe our use of laser-induced fluorescence imaging of a magnetically confined UCNP to obtain spatially resolved measurements of ion density, hydrodynamic flow velocity, temperature, and spin polarization. Our observations demonstrate the ions are highly spin-polarized immediately after plasma creation, and the spin polarization is long-lived throughout plasma expansion and confinement. |
Thursday, June 3, 2021 8:36AM - 8:48AM Live |
Q06.00004: Electrometry of a single resonator mode at a hybrid Rydberg-atom superconducting-circuit interface Dan Walker, Luke Brown, Stephen D Hogan Hybrid approaches to quantum information processing involve interfacing quantum systems with complementary characteristics, e.g., superconducting circuits for fast quantum-state manipulation, and gas-phase atoms or molecules for long coherence times [1]. In this context we recently demonstrated a coherent interface between helium Rydberg atoms and microwave fields in a superconducting coplanar waveguide resonator [2,3]. Here, we report the extension of this work to perform electrometry at this interface, using the atoms to probe the spatial distribution of the microwave field of a single resonator mode, and precisely measure static electric fields by Ramsey spectroscopy. These results have elucidated sources of decoherence of the atomic states, and in the interaction of the atoms with the resonator field. They pave the way for the implementation of long-coherence-time quantum memories and optical-to-microwave photon conversion in this hybrid system. |
Thursday, June 3, 2021 8:48AM - 9:00AM Live |
Q06.00005: Towards an Optogalvanic Trace Gas Sensor Based on Rydberg Excitation Patrick Kaspar, Fabian Munkes, Yannick Schellander, Joshua Fabian, Malte Kasten, Luana Rubino, Denis Djekic, Patrick Schalberger, Holger Baur, Robert Loew, Tilman Pfau, Jens Anders, Norbert Frühauf, Edward R Grant, Harald Kuebler We demonstrate the applicability of a new kind of gas sensor employing state of the art continuous wave lasers and current detection in a trace gas sensor prototype. From an unknown mixture of gas the molecule in question is excited to a Rydberg state and subsequently ionized by collisions with all other gas components. The emerging charges can be measured as a current which is then a clear signature of the presence of this particular molecule. |
Thursday, June 3, 2021 9:00AM - 9:12AM Live |
Q06.00006: Two-Color Optical Nonlinearity in an Ultracold Rydberg Atom Gas Mixture Cheng Chen, Fan Yang, Xiaoling Wu, Meng Khoon Tey, Li You Recent progresses on Rydberg atoms have significantly advanced their applications to quantum computation, quantum simulation, and quantum optics. Most systems studied so far are based on single atomic species. In this work, we report the experimental observation of strong two-color optical nonlinearity in an ultracold gas of 85Rb-87Rb atom mixture. By coupling light fields of two different frequencies respectively to Rydberg states of 85Rb and 87Rb atom via two distinct EIT pathways, we map the Rydberg interaction between different atomic species onto photonic interaction between two nondegenerate optical modes. Such a cross-absorption modulation can be described by a two-component nonlinear wave equations we develope. We further demonstrate that the two-color optical nonlinearity can be tuned by varying the density ratio of different atomic isotopes, which highlights its potential for exploring strongly interacting multi-component fluids of light. Our work opens up an exciting avenue towards generating strong cross-Kerr nonlinearity between two-color optical modes with ultracold atom gas mixture, and the potential of generating quantum correlation between two photons using strong Rydberg atom-atom interaction as a bridge to connect light fields of different colors. |
Thursday, June 3, 2021 9:12AM - 9:24AM Live |
Q06.00007: Chiral Spin Liquid in a hexagonal Lattice of Rydberg Atoms with density-dependent Peierls Phases Simon Ohler, Maximilian Kiefer-Emmanouilidis, Michael Fleischhauer Recently, experiments demonstrated that spin-orbit coupling in systems of Rydberg atoms gives rise to Peierls phases in the hopping of Rydberg excitations that feature a density-dependence [Lienhard et al., PRX 10, 021031 (2020)]. In this talk we expand on this concept and analyze theoretically a two-dimensional hexagonal (honeycomb) lattice of identical spin-orbit coupled Rydberg atoms exhibiting density-dependent hopping terms. We numerically investigate the phase diagram by modifying the strength of the density-dependent terms and propose order parameters to identify the phase transitions. In the regime where density-dependent and direct hopping processes are comparable in strength, we find evidence for a chiral spin liquid (CSL) phase. |
Thursday, June 3, 2021 9:24AM - 9:36AM Live |
Q06.00008: Quantifying the Impact of State Mixing on the Rydberg Excitation Blockade Aaron Reinhard, Milo Eder, Andrew Lesak, Abigail E Plone, Tomohisa Yoda, Michael A Highman The Rydberg excitation blockade has enabled impressive achievements in quantum information and simulation. However, unwanted processes may compromise the single-excitation behavior of the blockade and reduce its efficiency. We study one such process, state-mixing interactions. When ultracold atoms are excited to Rydberg states near Förster resonance, up to ∼ 50% of the detected atoms can be found in dipole coupled product states within tens of ns of excitation. There has been disagreement in the literature regarding the mechanism by which this mixing occurs. We use state-selective field ionization spectroscopy with single-event resolution to probe state mixing near the 43D5/2 Förster resonance in Rb. Our method allows us to quantify both the number of additional excitations added by each mixing event, as well as the extent to which state mixing “breaks” the blockade. |
Thursday, June 3, 2021 9:36AM - 9:48AM Live |
Q06.00009: Four-level, all infrared, Doppler-free Rydberg EIT in rubidium Brielle E Anderson, Donald P Fahey, David H Meyer, Kevin C Cox, Paul Kunz Four-level, three-photon ladder Rydberg EIT has several potential advantages over the more popular two-photon Rydberg EIT in its applications to field sensing and non-classical photon state generation. In warm vapors, Doppler-free alignments leading to zero-velocity spin waves or expanded velocity class inclusion are possible with three-photon EIT but require further experimental investigation. We present experiments in warm vapors using an all-infrared scheme and discuss prospects for electric field sensing and exploring interactions between thermal Rydberg atoms. |
Thursday, June 3, 2021 9:48AM - 10:00AM Live |
Q06.00010: Rydberg atom-ion collisions in cold environments Henrik Hirzler, Jesus Perez Rios In this work, we investigate the parameter space associated with different plausible approaches for the dynamics of Rydberg-ion collisions as a collision energy function. As a result, we find that at the lowest reachable temperatures in ultracold systems, a classical treatment is appropriate to study such systems' dynamics. In particular, we have developed a quasi-classical trajectory approach to study charge exchange and l-mixing collisions for Li*-Li+ and Li*-Cs+ at collision energies down to 1K. For cold collisions, we find the charge exchange cross section deviating from the n4 geometric scaling. Furthermore, we find both an influence of the ionic core-repulsion and variations for two different models used for describing the electron-core potential for low-energy collisions. |
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