# Dynamical Gauge Fields

Within the Standard Model of Particle Physics, the interaction between fundamental particles is described by gauge theories. These theories have an enormous predictive power, but to compute the dynamics they generate is an extremely hard task. As a consequence, high-energy physics contains many unsolved problems such as quark confinement or the dynamics of quarks and gluons during heavy-ion collisions. Instead of computing them in classical devices or investigating them in enormous accelerator facilities, we aim at implementing lattice gauge theories on the optical table by having atomic gases in optical lattices mimic the interplay between particles, anti-particles, and gauge bosons. In this way, experiments at temperatures just above absolute zero could give insights into unsolved phenomena that in Nature appear at very high energies.

### A short (mathy) introduction

We wrote a blog post to give an introduction into the ideas underlying dynamical gauge fields. If you feel like it please take a look.

more ...Philipp Hauke

Phone: +49 6221 54 5185

philipp.hauke@kip.uni-heidelberg.de

Michael Adrian Jendrusch

Phone: +49 6221 54 9176

michael.jendrusch@kip.uni-heidelberg.de

Fred Jendrzejewski

Phone: +49 6221 54 5182

fnj@kip.uni-heidelberg.de

Alexander Mil

Phone: +49 6221 54 5175

alexander.mil@kip.uni-heidelberg.de

Markus Oberthaler

Phone: +49 6221 54 5170

markus.oberthaler@kip.uni-heidelberg.de

Fabian Olivares

Phone: +49 6221 54 5175

fdolivar@kip.uni-heidelberg.de

## Recent publications

### Quantum simulation of lattice gauge theories using Wilson fermions

HD-KIP 18-09, 2018, Quantum Sci. Technol. (3) 034010 PDF-DateiQuantum simulators have the exciting prospect of giving access to real-time dynamics of lattice gauge theories, in particular in regimes that are difficult to compute on classical computers. Future progress towards scalable quantum simulation of lattice gauge theories, however, hinges crucially on the efficient use of experimental resources. As we argue in this work, due to the fundamental non-uniqueness of discretizing the relativistic Dirac Hamiltonian, the lattice representation of gauge theories allows for an optimization that up to now has been left unexplored. We exemplify our discussion with lattice quantum electrodynamics in two-dimensional space-time, where we show that the formulation through Wilson fermions provides several advantages over the previously considered staggered fermions. Notably, it enables a strongly simplified optical lattice setup and it reduces the number of degrees of freedom required to simulate dynamical gauge fields. Exploiting the optimal representation, we propose an experiment based on a mixture of ultracold atoms trapped in a tilted optical lattice. Using numerical benchmark simulations, we demonstrate that a state-of-the-art quantum simulator may access the Schwinger mechanism and map out its non-perturbative onset.

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### Implementing quantum electrodynamics with ultracold atomic systems

HD-KIP 17-10, 2017, New Journal of Physics (19) 023030 PDF-DateiWe discuss the experimental engineering of model systems for the description of QED in one spatial dimension via a mixture of bosonic

^{23}Na and fermionic^{6}Li atoms. The local gauge symmetry is realized in an optical superlattice, using heteronuclear boson-fermion spin-changing interactions which preserve the total spin in every local collision. We consider a large number of bosons residing in the coherent state of a Bose-Einstein condensate on each link between the fermion lattice sites, such that the behavior of lattice QED in the continuum limit can be recovered. The discussion about the range of possible experimental parameters builds, in particular, upon experiences with related setups of fermions interacting with coherent samples of bosonic atoms. We determine the atomic system's parameters required for the description of fundamental QED processes, such as Schwinger pair production and string breaking. This is achieved by benchmark calculations of the atomic system and of QED itself using functional integral techniques. Our results demonstrate that the dynamics of one-dimensional QED may be realized with ultracold atoms using state-of-the-art experimental resources. The experimental setup proposed may provide a unique access to longstanding open questions for which classical computational methods are no longer applicable.### Observation of the Phononic Lamb Shift with a Synthetic Vacuum

HD-KIP 16-100, 2016, Physical Review X (6) 041041 PDF-DateiIn contrast to classical empty space, the quantum vacuum fundamentally alters the properties of embedded particles. This paradigm shift allows one to explain the discovery of the celebrated Lamb shift in the spectrum of the hydrogen atom. Here, we engineer a synthetic vacuum, building on the unique properties of ultracold atomic gas mixtures, offering the ability to switch between empty space and quantum vacuum. Using high-precision spectroscopy, we observe the phononic Lamb shift, an intriguing many-body effect originally conjectured in the context of solid-state physics. We find good agreement with theoretical predictions based on the Fröhlich model. Our observations establish this experimental platform as a new tool for precision benchmarking of open theoretical challenges, especially in the regime of strong coupling between the particles and the quantum vacuum.

### Schwinger pair production with ultracold atoms

HD-KIP 16-72, 2016, Physics Letters B (760) 742-746 PDF-DateiWe consider a system of ultracold atoms in an optical lattice as a quantum simulator for electron–positron pair production in quantum electrodynamics (QED). For a setup in one spatial dimension, we investigate the nonequilibrium phenomenon of pair production including the backreaction leading to plasma oscillations. Unlike previous investigations on quantum link models, we focus on the infinite-dimensional Hilbert space of QED and show that it may be well approximated by experiments employing Bose–Einstein condensates interacting with fermionic atoms. Numerical calculations based on functional integral techniques give a unique access to the physical parameters required to realize QED phenomena in a cold atom experiment. In particular, we use our approach to consider quantum link models in a yet unexplored parameter regime and give bounds for their ability to capture essential features of the physics. The results suggest a paradigmatic change towards realizations using coherent many-body states for quantum simulations of high-energy particle physics phenomena.

## Theses

- Nitrogen Vacancy Center Magnetometry as a New Approach for an Active Magnetic Field Control

Kerim Köster, Bachelorarbeit, 2018 PDF-File - Simulation and Measurements of Single and Coupled Coaxial Qubits

Tanja Behrle, Masterarbeit, 2018 PDF-File - Design and Implementation of a Versatile Imaging Objective for Imaging of Ultracold Mixtures of Sodium and Lithium

Alexander Mil, Masterarbeit, 2016 PDF-File - Spin Dynamics and Feshbach Resonances in Ultracold Sodium-Lithium Mixtures

Arno Trautmann, Dissertation, 2016 PDF-File - Observation of the Phononic Lamb Shift in a Synthetic Vacuum

Tobias Rentrop, Dissertation, 2016 PDF-File - Active Magnetic Field Stabilisation for Ultracold
Sodium Lithium Mixtures

Marcell Gall, Masterarbeit, 2015 PDF-File - Dynamics and Motional Coherence of Fermions Immersed in a Bose Gas

Raphael Scelle, Dissertation, 2013 PDF-File - Feshbach Resonances and Periodic Potentials in Ultracold Bose-Fermi Mixtures

Tobias Schuster, Dissertation, 2012 PDF-File - Immersed Quantum Systems: A Sodium Bose-Einstein Condensate for Polaron Studies

Jens Appmeier, Dissertation, 2010 PDF-File - Zeeman-Slower und Experimentsteuerung für das NaLi-Experiment

Jan Krieger, Diplomarbeit, 2008 PDF-File - Setup of a Laser System for Ultracold Sodium - Towards a Degenerate Gas of Ultracold Fermions

Stefan Weis, Diplomarbeit, 2007

DFG: Systematische Verbesserung von Atom Trap Trace Anlaysis für 39Ar und deren Anwendung zur Erstellung einer tausendjährigen Paläotemperaturzeitreihe aus Grundwasser

DFG: ArTTA-10mL: Ein Instrument für die 39Ar-Datierung von kleinen Eis- und Wasserproben