Bulletin of the American Physical Society
2021 Fall Meeting of the APS Division of Nuclear Physics
Volume 66, Number 8
Monday–Thursday, October 11–14, 2021; Virtual; Eastern Daylight Time
Session JN: Mini-Symposium: Quantum Information Science and Nuclear Theory IV: Gauge Theories |
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Chair: Martin Savage, UW-Seattle Room: Studio 1 |
Wednesday, October 13, 2021 9:30AM - 9:42AM |
JN.00001: Staircase prethermalization and gauge stabilization in lattice gauge theories Jad C Halimeh The dynamics of lattice gauge theories is characterized by an abundance of local symmetry constraints. Although errors that break gauge symmetry appear naturally in modern quantum simulators, their influence on the gauge-theory dynamics is insufficiently investigated. In this talk, we show that a small gauge breaking of strength λ induces a staircase of long-lived prethermal plateaus. The number of prethermal plateaus increases with the number of matter fields L, with the last plateau being reached at a timescale λ-L/2, indicating an intimate relation of the concomitant slowing down of dynamics with the number of local gauge constraints. By means of a Magnus expansion, we demonstrate how exact resonances between different gauge-invariant supersectors are the main reason behind the emergence of staircase prethermalization. We then discuss experimentally feasible gauge protection schemes based on energy constraints for the stabilization of gauge invariance in the presence of such errors, showing numerically and analytically the emergence of exact gauge theories up to timescales polynomial and even exponential in a volume-independent protection strength. We showcase such schemes in an experimental realization of a U(1) lattice gauge theory on a 71-site Bose--Hubbard quantum simulator. |
Wednesday, October 13, 2021 9:42AM - 9:54AM |
JN.00002: Digitizing Gauge Invariant Interactions, II: Quantum Algorithms for SU(2) Gauge Fields and Matter in (1+1)D Alexander Shaw, Jesse Stryker, Zohreh Davoudi We present scalable quantum algorithms to simulate (1+1)D SU(2) lattice gauge theory in both near-term and far-term quantum resource scenarios. In these scenarios, we compare the cost of the algorithms, along with their development and analysis to that of algorithms for simulating U(1) lattice gauge theory in (1+1)D. This presentation focuses on the gauge-fermion interaction ("hopping") terms, for which the generalization from U(1) to SU(2) is the most involved. We use the block-diagonalized interaction terms for both U(1) and SU(2), as discussed in J. Stryker's presentation, and give quantum algorithms which implement them while conserving the largest possible set of commuting gauge constraints. |
Wednesday, October 13, 2021 9:54AM - 10:06AM |
JN.00003: High-energy physics at ultracold temperatures Daniel González-Cuadra, Maciej Lewenstein, Alejandro Bermudez, Alexandre Dauphin, Luca Tagliacozzo, Monika Aidelsburger Understanding the nature of confinement, as well as its relation with the spontaneous breaking of chiral symmetry, remains one of the long-standing questions in high-energy physics. The difficulty of these task stems from the limitations of current analytical and numerical techniques to address nonperturbative phenomena in non-Abelian gauge theories. The situation becomes particularly problematic when trying to analize the phase diagram of QCD at large Baryon densities, where a confinement-deconfinement transition between the hadronic and the quark-gluon plasma phases takes place. Recent progress with atomic quantum simulators indicates an alternative direction to overcome these limitations. In this talk, I will present two different approaches to address the physics of confinement using near-term quantum devices. In the first one, I will consider one of the simplest gauge theories in the presence of dynamical matter, and I will show how, using ideas drawn from topology, deconfinemened states can be prepared using less experimental resources [1]. In the second one, I will show how particle physics phenomenology emerges in even simpler models that do not possess gauge invariance [2], and are thus simpler to implement with atomic systems such as ultracold atoms in optical lattices. This would allow to study, for instance, confinement-deconfinement transitions and chiral symmetry restoration under controllable experimental conditions. |
Wednesday, October 13, 2021 10:06AM - 10:18AM |
JN.00004: Digitizing gauge invariant interactions, I: Conserving Abelian constraints with shears Jesse Stryker Universal quantum simulations of gauge field theories are exposed to the risk of gauge symmetry violations when it is not known how to compile the desired operations exactly using the available gate set. In this talk, we discuss how interactions can be compiled -- if only approximately -- without compromising Abelian constraints by graphically motivating a block-diagonalization procedure. When gauge invariant interactions can be associated with a "spatial network" in the space of discrete quantum numbers, it is seen that cyclically shearing the spatial network converts simultaneous updates to many quantum numbers into conditional updates of a single quantum number: ultimately, this eliminates any need to pass through (and acquire overlap onto) symmetry-violating intermediate configurations. As examples, we look at how shears can be applied to gauge-matter interactions in (1+1)-dimensional U(1) and SU(2) gauge theories. |
Wednesday, October 13, 2021 10:18AM - 10:30AM |
JN.00005: Lattice QIS: Euclidean Methods for Minkowski Calculations Henry S Lamm The possibility for near-term quantum simulations in lattice field theory depends upon efficiently using the limited resources available. For the forseeable future, connecting toN large-scale classical simulations in Euclidean lattice field theory may prove invaluable. In this talk, we will discuss how approximating lattice gauge theories like SU(3) with discrete subgroups can be theoretically analyzed as a lattice effective field theory, and how the critical step of scale setting on quantum computers may be aided by Euclidean calculations. Methods for implementation upon quantum hardware will be covered. Numerical results for Euclidean and Minkowski calculation will be presented with modified and improved actions that relate to Hamiltonians other than Kogut and Susskind. |
Wednesday, October 13, 2021 10:30AM - 10:42AM |
JN.00006: Space-time symmetric qubit regularization of asymptotically freedom Tanmoy Bhattacharya, Shailesh Chandrasekharan, Rajan Gupta, Hersh Singh, Junzhe Zhou We explore if space-time symmetric lattice field theory models with a finite Hilbert space per lattice site can reproduce asymptotic freedom. To make things concrete we consider the continuum two dimensional O(4) model which is asymptotically free. Within a class of simple lattice models, we discover a model with a four dimensional local Hilbert space that can reproduce the step scaling function of the continuum model up to correlation lengths of about 50 lattice sites. As expected this requires some fine tuning, without which the correlation lengths reached are usually much smaller. On the other hand, using D-theory ideas we can reach systematically larger correlations, but this naturally increases the Hilbert space per site. We argue that while the D-theory approach increases the local Hilbert space, the complexity of quantum computation is likely to be manageable due to locality in the extra dimension. However, the search for a space-time symmetric lattice model with a finite fixed local Hilbert space that reproduces the step scaling function for arbitrarily large correlation lengths remains ongoing. |
Wednesday, October 13, 2021 10:42AM - 10:54AM |
JN.00007: Quantum Simulation of Light-Front Parton Correlators Enrique Rico Ortega, Gunar Schnell, Iñigo L Egusquiza, Miguel G Echevarria The physics of high-energy colliders relies on the knowledge of different non-perturbative parton correlators, such as parton distribution functions, that encode the information on universal hadron structure and are thus the main building blocks of any factorization theorem of the underlying process in such collision. These functions are given in terms of gauge-invariant light-front operators, they are non-local in both space and real-time, and are thus intractable by standard lattice techniques due to the well-known sign problem. In this paper, we propose a quantum algorithm to perform a quantum simulation of these type of correlators and illustrate it by considering a space-time Wilson loop. We discuss the implementation of the quantum algorithm in terms of quantum gates that are accessible within actual quantum technologies such as cold atoms setups, trapped ions or superconducting circuits. |
Wednesday, October 13, 2021 10:54AM - 11:06AM |
JN.00008: Overcoming the sign-problem with variational Monte-Carlo methods: a study of (2+1)-dimensional compact quantum electrodynamics Julian Bender, Patrick Emonts, Erez Zohar, J. Ignacio Cirac Studying lattice gauge theories with Monte-Carlo simulations based upon importance sampling has been a major success over several decades. Unfortunately, some theories of interest are affected by the sign problem which prevents the use of the aforementioned method so that certain questions cannot be addressed (e.g. finite chemical potential scenarios or real-time dynamics). Based on the Hamiltonian formulation of lattice gauge theory we develope a variational ansatz that is evaluated with Monte-Carlo methods but inherently sign problem free and study as a first step towards higher-dimensional gauge theories (2+1)-dimensional compact QED. First, we investigate real-time dynamics after various global quenches, with a focus on confinement and the equilibration of expectation values. To verify the ansatz, we benchmark for small system sizes against exact diagonalization. Secondly, we study (2+1)-dimensional compact QED with multiple flavors of massless fermions. We benchmark against standard Monte-Carlo simulations at an even number of fermion flavors where the sign problem is absent and then study the theory at an odd number of fermion flavors. We also discuss how these results can help in the design of future quantum simulators for gauge theories. |
Wednesday, October 13, 2021 11:06AM - 11:18AM |
JN.00009: Hamiltonian Simulation of Lattice Gauge Theories with Fermionic Tensor Networks and Monte Carlo Patrick Emonts, Mari Carmen Banuls, J. Ignacio Cirac, Erez Zohar Quantum simulation is based on the Hamiltonian formulation of lattice gauge theories. Classical Monte Carlo algorithms, however, mainly focus on the action formalism due to gains in computational efficiency. At the same time, they lose the possibility to describe real-time dynamics and may suffer from the sign problem. |
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