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 M07: Quantum Phases in Optical Lattices IILive
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Chair: Matthew Nichols, Harvard |
Wednesday, June 2, 2021 2:00PM - 2:12PM Live |
M07.00001: Doping two-dimensional Fermi-Hubbard systems from polaronic metal to Fermi liquid Sarah Hirthe, Joannis Koepsell, Dominik Bourgund, Pimonpan Sompet, Annabelle Bohrdt, Yao Wang, Fabian Grusdt, Eugene Demler, Guillaume Salomon, Christian Gross, Immanuel F Bloch The Fermi-Hubbard model is believed to capture the essential ingredients of phenomena like high-Tc superconductivity, yet a complete understanding of its phases emerging upon doping remains elusive. Using our Fermi gas microscope with full spin and density resolution, we investigate the influence of different doping levels in a two-dimensional antiferromagnetic Hubbard system at temperatures around the superexchange energy. We observe the crossover from an anomalous metal to a conventional Fermi liquid. In order to obtain a better understanding of the nature of charge carriers within this crossover, we study the transformation of multi-point correlations between spins and holes. Starting from a magnetic polaron regime, we find the system evolves into a Fermi liquid featuring incommensurate magnetic fluctuations and fundamentally altered correlations. The crossover is completed for hole dopings around 30%. We benchmark theoretical approaches and discuss possible connections to lower temperature phenomena. |
Wednesday, June 2, 2021 2:12PM - 2:24PM Live |
M07.00002: Site-Resolved Imaging of NaRb Feshbach Molecules in an Optical Lattice Jason S Rosenberg, Lysander Christakis, Zoe Yan, Waseem S Bakr Applying the technique of quantum gas microscopy to polar molecules presents an attractive platform for the quantum simulation of many-body systems with long-range interactions. Here, we present our work toward site-resolved imaging of 23Na87Rb Feshbach molecules in a 2D optical lattice. We prepare quasi-2D dual Na and Rb BECs in a highly anisotropic light sheet optical potential that provides tight vertical confinement. A bichromatic, tightly focused "dimple" trap allows us to reliably produce BECs with small, stable atom number. We load the dual BECs into a 2D optical lattice and ramp through a Feshbach resonance to produce a sparse gas of NaRb Feshbach molecules, optically removing remaining atoms. The molecules are dissociated in the lattice for site-resolved fluorescence imaging of Rb atoms. In future work, we will overlap dual Mott insulators of Na and Rb to form a low-entropy array of NaRb Feshbach molecules. We also plan to coherently transfer the weakly-bound molecules to the absolute ground state, realizing a platform for single-site detection and manipulation of polar molecules. |
Wednesday, June 2, 2021 2:24PM - 2:36PM Live |
M07.00003: Quantum gas microscopy of three-dimensional systems Luca Asteria, Henrik P Zahn, Marcel Kosch, Klaus Sengstock, Christof Weitenberg Imaging of quantum gases in optical lattices with single-site resolution has provided new ways to study quantum many-body systems. However, such microscopy was mainly restricted to two-dimensional systems. Here we present a new microscopy method, which overcomes the limitations of depth of focus and of parity projection and allows imaging three-dimensional systems with single lattice site resolution and we apply it to Bosons in an array of tubes, i.e. a Josephson junction array. We demonstrate the great potential of the new method for investigating diverse directions in lattice physics. |
Wednesday, June 2, 2021 2:36PM - 2:48PM Not Participating |
M07.00004: Topological semimetal and superfluid of s-wave interacting fermionic atoms in an orbital optical lattice Maksims Arzamasovs, Shuai Li, W. Vincent Liu, Bo Liu Recent advanced experimental implementations of optical lattices with highly |
Wednesday, June 2, 2021 2:48PM - 3:00PM Live |
M07.00005: Quantum register of fermion pairs Thomas R Hartke, Botond Oreg, Ningyuan Jia, Martin W Zwierlein Pairing of fermions lends stability and robustness to matter, from nuclei and atoms to superconductors and neutron stars. In this talk, we demonstrate the use of fermion pairs in an optical lattice for robust encoding and manipulation of quantum information. With each fermion pair forming a spin singlet, the qubit is realized as a set of degenerate, symmetry-protected, two-particle vibrational wavefunctions. Degeneracy is lifted by the atomic recoil energy of the optical lattice, rendering two-fermion motional qubits insensitive against noise in the confining potential. Our method provides a new route toward quantum computation and simulation by leveraging Pauli exclusion for high fidelity preparation and control of entangled motional states of fermions. |
Wednesday, June 2, 2021 3:00PM - 3:12PM Live |
M07.00006: Coherent control of fermion pair qubits Ningyuan Jia, Thomas R Hartke, Botond Oreg, Martin W Zwierlein Coherent control of entangled fermion pairs can serve as a promising physical resource for quantum simulation and computation. Here we experimentally demonstrate a robust quantum register comprised of hundreds of fermionic atom pairs trapped in an optical lattice. The qubit consists of a protected subspace of vibrational states, with a stable energy splitting given by the atomic recoil energy. We observe coherence times on the scale of ten seconds. Via coherent conversion of free atom pairs into tightly bound molecules, we tune the two-fermion gate speed over three orders of magnitude, yielding ~10,000 gates within the coherence time. The methods presented here open the door towards fermion-based quantum computation and fully controlled generation of large-scale entangled many-body states. |
Wednesday, June 2, 2021 3:12PM - 3:24PM Live |
M07.00007: Protected cat states in a driven superfluid boson gas. Fernando Sols, Jesús Mateos, Gregor Pieplow, Charles Creffield We investigate the behavior of a one-dimensional Bose-Hubbard gas in both a ring and a hard-wall box, whose kinetic energy is made to oscillate with zero time average, which suppresses first-order particle hopping while allowing even higher-order processes [1]. At a critical value of the driving, the system passes from a Mott insulator to an exotic superfluid phase. The system in the ring has similarities to the Richardson pairing model which can be exploited to understand key features of the interacting boson problem [2]. The superfluid ground state is a macroscopic quantum superposition, or cat state, of two many-body states characterized by the preferential occupation of opposite momentum eigenstates. Interactions give rise to a reduction (or modified depletion) cloud that is common to both macroscopically distinct states [2]. Symmetry arguments permit a precise identification of the two orthonormal many-body branches forming the ground state. In the ring, the system is sensitive to variations of the effective flux but in such a way that the macroscopic superposition is preserved. We discuss other physical aspects that contribute to protect the catlike nature of the ground state. We study the robustness of the effect against variations in the signal shape and switching protocol [3]. |
Wednesday, June 2, 2021 3:24PM - 3:36PM Live |
M07.00008: Topological Euler Class as a Dynamical Observable in Optical Lattices Nur Unal, Adrien Bouhon, Robert-Jan Slager The last years have witnessed rapid progress in the topological characterization of out-of-equilibrium systems. We report on robust signatures of a new type of topology—the Euler class—in such a dynamical setting. The enigmatic invariant (ξ) falls outside conventional symmetry-eigenvalue indicated phases and, in simplest incarnation, is described by triples of bands that comprise a gapless pair featuring 2ξ stable band nodes, and a gapped band. These nodes host non-Abelian charges and can be further undone by converting their charge upon intricate braiding mechanisms, revealing that Euler class is a fragile topology. We demonstrate that quenching with nontrivial Euler Hamiltonian results in stable monopole-antimonopole pairs, which in turn induce a linking of momentum-time trajectories under the first Hopf map, making the invariant experimentally observable. Detailing explicit tomography protocols in a variety of ultracold-atom setups, our results provide a basis for exploring new topologies and their interplay with crystalline symmetries in optical lattices beyond paradigmatic Chern insulators. |
Wednesday, June 2, 2021 3:36PM - 3:48PM Live |
M07.00009: Site-resolved imaging of ultracold fermions in a triangular-lattice quantum gas microscope Liyu Liu, Jirayu Mongkolkiattichai, Jin Yang, Peter Schauss Quantum gas microscopes have led to a new microscopic view on Hubbard systems. One milestone was the direct observation of antiferromagnetic correlations. Interestingly, Hubbard models on lattices with geometrically suppressed antiferromagnetic ordering show a wider variety of exotic quantum phases. A triangle is the paradigm configuration where antiferromagnetic constraints cannot be simultaneously satisfied on all bonds. In this talk, we present a fermionic microscope on a triangular lattice. We demonstrate the site-resolved imaging of ultracold fermionic 6Li atoms in a triangular lattice with lattice constant of 1003 nm demonstrating an imaging fidelity of 98% [1]. The optical lattice is formed by a recycled narrow-linewidth, high-power laser combined with a light sheet to allow for Raman sideband cooling on the D1 line. Our new experimental platform paves the way to the realization of exotic quantum phases including chiral spin liquids in triangular lattice Hubbard systems and their detection on the single-particle level. [1] J. Yang, et al., arXiv:2102.11862 (2021). |
Wednesday, June 2, 2021 3:48PM - 4:00PM Not Participating |
M07.00010: Signatures of phase transitions and optical bistability for atoms in optical lattices Christopher D Parmee, Janne Ruostekoski Radiative dipole-dipole interactions lead to a rich phenomenology of phases in an optical lattice of atoms when driven by a coherent field. They can also support intrinsic optical bistability, where it is possible for two such phases to coexist. Here, we investigate the different phases that emerge in an array of atoms and how they can be identified by studying the scattered light. We find that the onset of phases predicted by mean-field theory are revealed by large jumps in coherent and incoherent signals of the transmitted light. The presence of bistability can result in a strong cooperative and weak single-atom response from the array, with hysteresis upon sweeping the incident light frequency. We discuss how the phases depend on the low light intensity collective modes, and also determine the thresholds for the optical bistability in terms of the atomic cooperativity parameter and intensity of the incident light, in many cases obtaining analytical results. |
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