Lattice Gauge Theories and String Dynamics in Rydberg Atom Quantum Simulators

Abstract

Gauge theories are the cornerstone of our understanding of fundamental interactions among elementary particles. Their properties are often probed in dynamical experiments, such as those performed at ion colliders and high-intensity laser facilities. Describing the evolution of these strongly coupled systems is a formidable challenge for classical computers and represents one of the key open quests for quantum simulation approaches to particle physics phenomena. In this work, we show how recent experiments done on Rydberg atom chains naturally realize the real-time dynamics of a lattice gauge theory at system sizes at the boundary of classical computational methods. We prove that the constrained Hamiltonian dynamics induced by strong Rydberg interactions maps exactly onto the one of a U(1) lattice gauge theory. Building on this correspondence, we show that the recently observed anomalously slow dynamics corresponds to a string-inversion mechanism, reminiscent of the string breaking typically observed in gauge theories. This underlies the generality of this slow dynamics, which we illustrate in the context of one-dimensional quantum electrodynamics on the lattice. Within the same platform, we propose a set of experiments that generically show long-lived oscillations, including the evolution of particle-antiparticle pairs, and discuss how a tunable topological angle can be realized, further affecting the dynamics following a quench. Our work shows that the state of the art for quantum simulation of lattice gauge theories is at 51 qubits and connects the recently observed slow dynamics in atomic systems to archetypal phenomena in particle physics.

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Plain Language Summary

Gauge theories describe the fundamental forces of nature, from the electromagnetic interactions among charged particles to the strong interactions among quarks in nucleons. Despite the conceptual elegance of these theories, probing their predictions is a formidable task: Experiments require gigantic facilities such as the Large Hadron Collider at CERN, while numerical simulations demand extreme computational resources. To improve our understanding of fundamental forces, researchers are looking for tools to probe extreme regimes of matter in tabletop experiments. Promising candidates for such experiments include quantum simulators, for which cold-atom gases trapped by laser light are an ideal platform for implementation. Here, we show that an array of Rydberg atoms emulates a lattice gauge theory at system sizes that are difficult for classical computational methods.

The gauge theory in question is the Schwinger model, a theory for the quantum electrodynamics in one spatial dimension. In light of the connection between atomic physics experiments and gauge theories, we interpret the dynamics of Rydberg atoms observed in a recent experiment as a string inversion mechanism. This paradigmatic phenomenon represents a close counterpart of string breaking and describes how the dynamics of electrons and positrons is drastically affected by their interactions mediated by the electric field. We also propose a set of new experiments to simulate the dynamics of particle-antiparticle pairs and to dynamically observe the effects of confinement in gauge theories.

Our work points to a generic strategy that may soon be applied to the study of considerably more complex gauge theories such as those with “non-Abelian gauge symmetries,” akin to those describing strong nuclear forces—a grand challenge for quantum simulators.