Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session M61: Precision Many Body Physics I: Ultra-quantum MatterFocus
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Sponsoring Units: DCOMP Chair: Boris Svistunov, University of Massachusetts Amherst Room: Room 418 |
Wednesday, March 8, 2023 8:00AM - 8:36AM |
M61.00001: Engineering a topological gauge theory in an optically coupled Bose-Einstein condensate Invited Speaker: Leticia Tarruell Topological gauge theories describe the low-energy properties of certain strongly correlated quantum systems through effective weakly interacting models. A prime example is the Chern-Simons theory of fractional quantum Hall states, where anyonic excitations emerge from the coupling between weakly interacting matter particles and a density-dependent gauge field. While in traditional solid-state platforms such gauge theories are only convenient theoretical constructions, engineered quantum systems enable their direct implementation and provide a fertile playground to investigate their phenomenology without the need for strong interactions. In my talk, I will report on our recent realization of a one-dimensional reduction of the Chern-Simons theory (the chiral BF theory) in a Bose-Einstein condensate. Using the local conservation laws of the theory we eliminate the gauge degrees of freedom in favor of chiral matter interactions [1], which we engineer by synthesizing optically dressed atomic states with momentum-dependent scattering properties [2]. This allows us to reveal the key properties of the chiral BF theory: the formation of chiral solitons and the emergence of an electric field generated by the system itself [2]. Our results expand the scope of quantum simulation to topological gauge theories and pave the way towards implementing analogous gauge theories in higher dimensions. |
Wednesday, March 8, 2023 8:36AM - 8:48AM |
M61.00002: Quantum Physics in Highly Connected Worlds Joseph A Tindall, Dieter Jaksch, Amy Searle, Abdulla Alhajri Theoretical research into many-body quantum systems has mostly focused on either all-to-all models or regular structures which have a small, simple unit cell and where a vanishingly small number of pairs of the constituents directly interact. Motivated by advances in control over the pairwise interactions in many-body simulators, I will discuss the fate of many-body systems on more general, arbitrary graphs. In the spin case, I will present recent results which prove, when placing the minimum possible constraints on the underlying graph, such systems behave like a single collective spin in the thermodynamic limit. I will discuss the constraints necessary to violate these results and introduce hitherto unknown dense graphs where complex many-body physics emerges in the form of entanglement and highly non-uniform correlation functions. |
Wednesday, March 8, 2023 8:48AM - 9:00AM |
M61.00003: Simulating plasmonic behaviors in large fermionic arrays Keyi Liu, Garnett W Bryant, Emily A Townsend It is known that interesting plasmonic behavior can arise from small fermionic systems with Coulomb interactions. With techniques such as the Density Matrix Renormalization Group (DMRG), we explored the possibility of simulating 1-D fermionic systems with dimensions well beyond the limits of Exact Diagonalization (ED), and observing plasmonic behaviors, such as the asymptotically perfect quantization of plasmonic excitations, on scales that were previously numerically infeasible. With possible imperfect lattice realization in experiments in mind, we also studied the effects of disorder on these system, through combination of machine learning techniques and data from both ED and advanced tensor network algorithms. We observed the power of Convolutional Neural Network (CNN) in learning about the distribution of various localization metrics, as well as important many-body physical quantities such as the Generalized Plasmonicity Index. We concluded by comments on our current efforts in simulating larger 2-D fermionic systems as well as open systems. |
Wednesday, March 8, 2023 9:00AM - 9:12AM |
M61.00004: Learning Feynman Diagrams with Tensor Trains Olivier P Parcollet, Yuriel Nunez-Fernandez, Matthieu Jeannin, Philipp Dumitrescu, Thomas Kloss, Jason Kaye, Xavier Waintal We use tensor network techniques to obtain high order perturbative diagrammatic expansions for the quantum many-body problem at very high precision. The approach is based on a tensor train parsimonious representation of the sum of all Feynman diagrams, obtained in a controlled and accurate way with the tensor cross interpolation algorithm. It yields the full time evolution of physical quantities in the presence of any arbitrary time dependent interaction. Our benchmarks on the Anderson quantum impurity problem, within the real time non-equilibrium Schwinger-Keldysh formalism, demonstrate that this technique supersedes diagrammatic Quantum Monte Carlo by orders of magnitude in precision and speed, with convergence rates 1/N2 or faster, where N is the number of function evaluations. The method also works in parameter regimes characterized by strongly oscillatory integrals in high dimension, which suffer from a catastrophic sign problem in Quantum Monte-Carlo. Finally, we also present two exploratory studies showing that the technique generalizes to more complex situations: a double quantum dot and a single impurity embedded in a two dimensional lattice. |
Wednesday, March 8, 2023 9:12AM - 9:24AM |
M61.00005: Hyper-optimized compressed contraction of tensor networks with arbitrary geometry Johnnie Gray Tensor network contraction is central to problems ranging from many-body physics to computer science. We describe how to approximate tensor network contraction through bond compression on arbitrary graphs. In particular, we introduce a hyper-optimization over the compression and contraction strategy itself to minimize error and cost. We demonstrate that our protocol outperforms both hand-crafted contraction strategies as well as recently proposed general contraction algorithms on a variety of synthetic problems on regular lattices and random regular graphs. We further showcase the power of the approach by demonstrating compressed contraction of tensor networks for frustrated three-dimensional lattice partition functions, dimer counting on random regular graphs, and to access the hardness transition of random tensor network models, in graphs with many thousands of tensors. |
Wednesday, March 8, 2023 9:24AM - 9:36AM |
M61.00006: Reduced basis modeling for quantum spin systems based on DMRG Paul Brehmer, Michael Herbst, Matteo Rizzi, Benjamin Stamm, Stefan Wessel Within the reduced basis modeling approach, an effective low-dimensional subspace of a quantum many-body Hilbert space is constructed in order to investigate, e.g., the ground-state phase diagram. The basis of this subspace is built from solutions of snapshots, i.e., ground states corresponding to particular and well-chosen parameter values. Here, we show how a greedy-strategy to assemble the reduced basis and thus to select the parameter points can be implemented based on density-matrix-renormalization-group (DMRG) calculations. Once the reduced basis is computed, observables required for the computation of phase-diagrams can be computed with a computational complexity independent of the underlying Hilbert space for any parameter value. We illustrate the efficiency and accuracy of this approach for different one-dimensional quantum spin-S models with both S=1/2 and S=1, including anisotropic as well as biquadratic exchange interactions, leading to rich quantum phase diagrams. |
Wednesday, March 8, 2023 9:36AM - 9:48AM |
M61.00007: Extracting Off-Diagonal Order from Diagonal Basis Measurements Ehsan Khatami, Bo Xiao, Javier Robledo Moreno, Matthew Fishman, Dries Sels, Richard T Scalettar Quantum gas microscopy has developed into a powerful tool to explore strongly correlated quantum systems. However, discerning phases with topological or off-diagonal long range order requires the ability to extract these correlations from site-resolved measurements. In this talk, we show that a multi-scale complexity measure can pinpoint the transition to and from the bond ordered wave phase of the one-dimensional extended Hubbard model with an off-diagonal order parameter, sandwiched between diagonal charge and spin density wave phases, using only diagonal descriptors. We study the model directly in the thermodynamic limit using the recently developed variational uniform matrix product states algorithm, and draw our samples from degenerate ground states related by global spin rotations, emulating the projective measurements that are accessible in experiments. We discuss the implications of our results for the study of exotic phases using optical lattice experiments. |
Wednesday, March 8, 2023 9:48AM - 10:00AM |
M61.00008: Auxiliary-Field Quantum Monte Carlo for Calculating the Renyi and Accessible Entanglement Entropies Tong Shen, Hatem N Barghathi, Adrian G Del Maestro, Brenda M Rubenstein In this work, we introduce an Auxiliary-Field Quantum Monte Carlo algorithm to measure the Renyi and accessible entanglement entropy (EE) for systems of interacting fermions in both the canonical and grand canonical ensembles. This approach generalizes a recursive method we recently developed for performing AFQMC in the canonical ensemble to enable replica sampling for systems and subsystems with a fixed particle number, which allows for the measurement of the Renyi and particle-number-resolved accessible EEs. We present comparisons of the EEs in the two different ensembles as a function of the interaction strength and temperature to illustrate how the entanglements can be affected by explicit particle number constraints. Furthermore, we demonstrate how the EEs can be used as accurate probes of first-order phase transitions. |
Wednesday, March 8, 2023 10:00AM - 10:12AM Author not Attending |
M61.00009: The Singular Euler-Maclaurin expansion on finite crystals Kirill Serkh, Andreas A Buchheit, Torsten Keßler In this work, we show how boundary effects in long-range interacting lattice systems can be efficiently computed. We generalize the recently developed Singular Euler-Maclaurin expansion to crystals with boundaries, where the lattice contribution on top of the integral approximation is given in terms of truncated Epstein zeta functions. We present a new, exponentially convergent algorithm for the computation of the arising truncated Epstein zeta functions, and apply our approach to several physically relevant examples. |
Wednesday, March 8, 2023 10:12AM - 10:24AM |
M61.00010: Robust analytic continuation methods for Green's functions via projection, pole estimation, and semidefinite relaxation Zhen Huang, Lin Lin, Emanuel C Gull Green's functions of fermions are described by matrix-valued Herglotz-Nevanlinna functions. Since analytic continuation is fundamentally an ill-posed problem, the causal space described by the matrix-valued Herglotz-Nevanlinna structure can be instrumental in improving the accuracy and in enhancing the robustness with respect to noise. We demonstrate a three-pronged procedure for robust analytic continuation called PES: (1) Projection of data to the causal space. (2) Estimation of pole locations. (3) Semidefinite relaxation within the causal space. We compare the performance of PES with the recently developed Nevanlinna and Carathéodory continuation methods and find that PES is more robust in the presence of noise and does not require the usage of extended precision arithmetics. We also demonstrate that a causal projection improves the performance of the Nevanlinna and Carathéodory methods. The PES method is generalized to bosonic response functions, for which the Nevanlinna and Carath´eodory continuation methods have not yet been developed. It is particularly useful for studying spectra with sharp features, as they occur in the study of molecules and band structures in solids. |
Wednesday, March 8, 2023 10:24AM - 10:36AM |
M61.00011: Non-linear response of interacting bosons in a quasiperiodic potential Kush Saha, Debamalya Dutta, Arko Roy We theoretically study the electric pulse-driven non-linear response of interacting bosons loaded in an optical lattice in the presence of an incommensurate superlattice potential. In the non-interacting limit (U=0), the model admits both localized and delocalized phases depending on the strength of the incommensurate potential V0. We show that the particle current contains only odd harmonics in the delocalized phase in contrast to the localised phase where both even and odd harmonics are identified. The relative magnitudes of these even and odd harmonics and sharpness of the peaks can be tuned by varying frequency and the number of cycles of the applied pulse, respectively. In the presence of repulsive interactions, the amplitudes of the even and odd harmonics further depend on the relative strengths of the interaction U and the potential V0. We illustrate that the disorder and interaction-induced phases can be distinguished and characterized through the particle current. Finally, we discuss the dynamics of field induced excitation responsible for exhibiting higher harmonics in the current spectrum. |
Wednesday, March 8, 2023 10:36AM - 10:48AM |
M61.00012: Abstract Submitted for the DAMOP23 Meeting of The American Physical Society Peng Du Benchmarking a high-precision quantum operation is a big challenge for many quantum systems in the presence of various noises as well as control errors. Here we propose an $O(1)$ benchmarking of a dynamically corrected rotation by taking the quantum advantage of a squeezed spin state in a spin-1 Bose-Einstein condensate. Our analytical and numerical results show that tiny rotation infidelity, defined by $1-F$ with $F$ the rotation fidelity, can be calibrated in the order of $1/N^2$ by only several measurements of the rotation error for $N$ atoms in an optimally squeezed spin state. Such an $O(1)$ benchmarking is possible not only in a spin-1 BEC but also in other many-spin or many-qubit systems if a squeezed or entangled state is available. |
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