Bulletin of the American Physical Society
47th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 61, Number 8
Monday–Friday, May 23–27, 2016; Providence, Rhode Island
Session C6: Quantum Gas Microscope |
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Chair: Gretchen Campbell, JQI Room: 552AB |
Tuesday, May 24, 2016 2:00PM - 2:12PM |
C6.00001: Microscopic Observation of Pauli Blocking in Degenerate Fermionic Lattice Gases Timon Hilker, Ahmed Omran, Martin Boll, Guillaume Salomon, Immanuel Bloch, Christian Gross Ultracold atoms in optical lattices provide a powerful platform for the controlled study of quantum many-body physics. We present here the first studies with a new generation quantum gas microscope, which allows to observe the full atom number statistics on every site. The common problem of light induced losses during imaging is avoided by an additional small scale \mbox{''}pinning lattice\mbox{''} used for Raman sideband cooling in the imaging process. We report the local observation of the Pauli exclusion principle in a spin-polarized degenerate gas of $^6$Li fermions in an optical lattice. In the band insulating regime, we measure a tenfold suppression of particle number fluctuations per site compared to classical particles. From the remaining fluctuations we extract a local entropy as low as 0.3 $k_B$ per atom. Our work opens an exciting avenue for studying local density and even magnetic correlations in fermionic quantum matter both in and out of equilibrium. [Preview Abstract] |
Tuesday, May 24, 2016 2:12PM - 2:24PM |
C6.00002: Measurement-induced control using a nondestructive quantum gas microscope Ivaylo S. Madjarov, Minwoo Jung, Jacob Rabinowitz, Zoe Wellner, Huiyao Y. Chen, Hil F. H. Cheung, Yogesh Sharad Patil, Mukund Vengalattore We present progress toward a quantum gas microscope that extends the paradigm of single-site imaging to one of single-site control. The basis for this scheme is our work on nondestructive lattice imaging and measurement-induced localization [1,2], where we show that lattice dynamics can be influenced by continuous measurement. The combination of nondestructive in situ imaging, single-site resolution, and spatially nonuniform measurement landscapes presents exciting prospects for new experimental studies of quantum thermodynamic processes that utilize information, such as the Szilard engine [3]. We present our recent results towards experimental realizations of such systems. \\[4pt] [1] Y. S. Patil \em et al. \em\ PRA 90, 033422 (2014) \newline [2] Y. S. Patil \em et al. \em\ PRL 115, 140402 (2015) \newline [3] S. W. Kim \em et al. \em\ PRL 106, 070401 (2011) [Preview Abstract] |
Tuesday, May 24, 2016 2:24PM - 2:36PM |
C6.00003: Quantum gas microscopy of the interacting Harper-Hofstadter system M. Eric Tai, Alex Lukin, Philipp Preiss, Matthew Rispoli, Robert Schittko, Adam Kaufman, Markus Greiner At the heart of many topological states is the underlying gauge field. One example of a gauge field is the magnetic field which causes the deflection of a moving charged particle. This behavior can be understood through the Aharonov-Bohm phase that a particle acquires upon traversing a closed path. Gauge fields give rise to novel states of matter that cannot be described with symmetry breaking. Instead, these states, e.g. fractional quantum Hall (FQH) states, are characterized by topological invariants, such as the Chern number. In this talk, we report on experimental results upon introducing a gauge field in a system of strongly-interacting ultracold Rb87 atoms confined to a 2D optical lattice. With single-site resolution afforded by a quantum gas microscope, we can prepare a fixed atom number and project hard walls. With an artificial gauge field, this quantum simulator realizes the Harper-Hofstadter Hamiltonian. We can independently control the two tunneling strengths as well as dynamically change the flux. This flexibility enables studies of topological phenomena from many perspectives, e.g. site-resolved images of edge currents. With the strong on-site interactions possible in our system, these experiments will pave the way to observing FQH-like states in a lattice. [Preview Abstract] |
Tuesday, May 24, 2016 2:36PM - 2:48PM |
C6.00004: A Quantum Gas Microscope for Fermionic Potassium Lawrence Cheuk, Matthew Nichols, Melih Okan, Katherine Lawrence, Hao Zhang, Martin Zwierlein Ultracold atoms in optical lattices have enabled experimental studies of quantum many-body physics in Hubbard-type lattice systems in a clean and well-controlled environment. In particular, the advent of quantum gas microscopes has made available new experimental probes ideally suited for observing magnetic order and spatial correlations. In the past year, several groups, including ours, first realized quantum gas microscopes for fermionic atoms. In this talk, we describe our experimental setup, which combines high-resolution imaging with Raman sideband cooling to achieve single-site-resolved fluorescent imaging of fermionic $^{40}$K atoms. We also report on recent progress towards observing quantum phases of the Fermi-Hubbard model with single-site resolution. [Preview Abstract] |
Tuesday, May 24, 2016 2:48PM - 3:00PM |
C6.00005: Imaging and addressing of individual fermionic atoms in an optical lattice Stefan Trotzky, Graham Edge, Rhys Anderson, Peihang Xu, Vijin Venu, Dylan Jervis, Dave McKay, Ryan Day, Joseph Thywissen The implementation of site-resolved imaging of atoms in short-period optical lattices constitutes a milestone achievement in the study of strongly correlated matter with these systems. Its realization with bosons six years ago has boosted progress in the field. In the last year, site-resolved imaging was demonstrated for fermions in five independent experiments. We present our newest results on site-resolved microscopy of ultracold $^{40}$K in a 527nm-period optical lattice. Atoms remain pinned during imaging due to EIT cooling on the 770nm D1 transition. We observe pinning fidelities of up to 96\% for an illumination time of 2.6s during which the atoms scatter $>$2000 photons. A 0.8NA objective collects the fluorescence light to be imaged onto a EMCCD camera, giving a 600nm -wide PSF. In conjunction with the known lattice geometry, this allows us to reconstruct the lattice-site occupations from the images. The imaging technique is implemented in an apparatus capable of simulating the Fermi-Hubbard model. The use of tomographic tools enables us to select single lattice planes for background free imaging. We also address in-plane patterns with straight and circular boundaries in order to eliminate inhomogeneity effects on the imaging fidelity, or for controlled entropy removal. [Preview Abstract] |
Tuesday, May 24, 2016 3:00PM - 3:12PM |
C6.00006: Site-resolved imaging of a fermionic Mott insulator Christie Chiu, Daniel Greif, Maxwell F. Parsons, Anton Mazurenko, Sebastian Blatt, Florian Huber, Geoffrey Ji, Markus Greiner Quantum gas microscopy of ultracold fermionic atoms in an optical lattice opens new perspectives for addressing long-standing open questions on strongly correlated low-temperature phases in the Hubbard model. Here we report on site-resolved imaging of two-component fermionic Mott insulators, metals, and band insulators with Lithium-6. For strong repulsive interactions we observe Mott insulators with more than 400 atoms and for intermediate interactions we observe a coexistence of phases. From comparison to theory, we find trap-averaged entropies per particle of $1.0\,k_{\mathrm{B}}$ in the Mott insulator and local entropies in the band insulator as low as $0.5\,k_{\mathrm{B}}$. Our measurements serve as a benchmark for the performance of our experiment and are a starting point for accessing the low-temperature regime of magnetic ordering. [Preview Abstract] |
Tuesday, May 24, 2016 3:12PM - 3:24PM |
C6.00007: Site-resolved measurement of spin correlations for fermions in an optical lattice Maxwell Parsons, Anton Mazurenko, Christie Chiu, Geoffrey Ji, Daniel Greif, Markus Greiner The recent demonstrations of site-resolved imaging of fermionic atoms in an optical lattice enable local measurements of charge correlations in Fermi lattice systems. Access to local spin correlations, however, has not yet been demonstrated. Measuring spin correlations is of particular interest because in the repulsive 2D Hubbard model, away from half-filling, the interplay of the spin and charge degrees of freedom is expected to give rise to pseudo-gap physics and perhaps d-wave superconductivity, but this doped regime is difficult to describe with current theoretical techniques. In this talk, I describe a new method for locally measuring spin correlations with our Fermi Gas Microscope. We observe nearest-neighbor AFM correlations in a two-component mixture of fermionic lithium atoms in a 2D optical lattice. The ability to measure trap-resolved magnetic correlations will allow us to explore entropy redistribution schemes, and may provide a way to access the low-temperature phases of the Hubbard model using ultracold atoms. [Preview Abstract] |
Tuesday, May 24, 2016 3:24PM - 3:36PM |
C6.00008: Defect-free atom arrays on demand Hannes Bernien, Alexander Keesling, Harry Levine, Eric Anschuetz, Crystal Senko, Vladan Vuletic, Markus Greiner, Manuel Endres, Mikhail D. Lukin Arrays of neutral, trapped atoms have proven to be an extraordinary platform for studying quantum many-body physics and implementing quantum information protocols. Conventional approaches to generate such arrays rely on loading atoms into optical lattices and require elaborate experimental control. An alternative, simpler approach is to load atoms into individual optical tweezers. However, the probabilistic nature of the loading process limits the size of the arrays to small numbers of atoms. Here we present a new method for assembling defect-free arrays of large numbers of atoms. Our technique makes use of an array of tightly focused optical tweezers generated by an acousto-optic deflector. The positions of the traps can be dynamically reconfigured on a sub-millisecond timescale. With single-site resolved fluorescence imaging, we can identify defects in the atom array caused by the probabilistic loading process and rearrange the trap positions in response. This will enable us to generate defect-free atom arrays on demand. We discuss our latest results towards reaching this goal along with schemes to implement long-range interactions between atoms in the array. [Preview Abstract] |
Tuesday, May 24, 2016 3:36PM - 3:48PM |
C6.00009: Preparing low-entropy Fermi-Hubbard systems with direct laser cooling Thomas Lompe, Phillip Wieburg, Christian Darsow-Fromm, Lennart Sobirey, Henning Moritz In recent years, few-particle systems of ultracold atoms have emerged as a viable tool for exploring strongly correlated quantum systems [1]. They allow to pursue a bottom-up approach by deterministically preparing small ground-state quantum systems and then using them as building blocks for assembling larger systems. Here we present a new experiment aimed at using Raman sideband cooling of $^{40}$K atoms in optical tweezers to prepare few-site Fermi-Hubbard systems with sub-second cycle times and probe them with single-site resolution [2]. \vspace{0.5 cm} \\ {[1] S. Murmann, A. Bergschneider, V. M. Klinkhamer, G. Z\"urn, T. Lompe, S. Jochim, Two Fermions in a Double Well: Exploring a Fundamental Building Block of the Hubbard Model, Phys. Rev. Lett. {\bf{114}}, 080402 (2015)} \\ {[2] L. W. Cheuk, M. A. Nichols, M. Okan, T. Gersdorf, V. V. Ramasesh, W. S. Bakr, T. Lompe, and M. W. Zwierlein, Quantum-Gas Microscope for Fermionic Atoms, Phys. Rev. Lett. {\bf{114}}, 193001 (2015)} [Preview Abstract] |
Tuesday, May 24, 2016 3:48PM - 4:00PM |
C6.00010: Improved trapping and transport of cold atoms for magnetic microscopy Amruta Gadge, T. James, X. Li, Bo Lu, N. GarridoGonzalez, A. Finke, C. Mellor, M. Fromhold, C. Koller, F. Orucevic, Peter Kruger Using cold atoms, a very sensitive and high resolution magnetic and electric field sensor can be realised. Ultra-close trapping of atoms would improve the resolution of cold-atom based surface probes. The limitation on the trapping distance arises from strongly distance-dependent effects such as Casimir force, Johnson noise etc. We are constructing an experimental system to trap atoms at surface separations of less than a micron. We will demonstrate the possibility of using special surfaces such as silicon nitride membranes and graphene for sub-micron trapping. We have designed a 10-layer printed circuit board, which can magnetically trap the cold atom cloud and transport it precisely to a desired location. This gives us the ability to study multiple samples within the same vacuum environment. In order to achieve higher atom number in the initial trapping stages, we use a dual-color MOT technique for Rb-87 atoms. Using this technique we achieve a significant increase in atom number and decrease in temperature. In this talk, I will present the results of the dual color MOT. I will also report on results related to magnetic transport and sub-micron trapping of atoms. [Preview Abstract] |
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