Continuum tensor network field states, path integral representations and the encoding of spatial symmetries

TL;DR

This paper develops a continuum tensor network framework for quantum field states, illustrating path integral representations, symmetry encoding, and the connection to entanglement entropy laws, bridging many-body physics, quantum field theory, and quantum information.

Contribution

It introduces a continuum tensor network approach for quantum fields, including a path integral representation and symmetry encoding, extending tensor network methods to quantum field theories.

Findings

All Fock space states can be represented as cMPS with infinite parameters.

A well-behaved field limit of PEPS in 2D provides a class of symmetric quantum field states.

Physical symmetries are encoded via auxiliary fields with Lorentz invariance.

Abstract

A natural way to generalise tensor network variational classes to quantum field systems is via a continuous tensor contraction. This approach is first illustrated for the class of quantum field states known as continuous matrix-product states (cMPS). As a simple example of the path-integral representation we show that the state of a dynamically evolving quantum field admits a natural representation as a cMPS. A completeness argument is also provided that shows that all states in Fock space admit a cMPS representation when the number of variational parameters tends to infinity. Beyond this, we obtain a well-behaved field limit of projected entangled pair states (PEPS) in two dimensions that provide an abstract class of quantum field states with natural symmetries. We demonstrate how symmetries of the physical field state are encoded within the dynamics of an auxiliary field system of one dimension less. In particular, the imposition of Euclidean symmetries on the physical system requires that the auxiliary system involved in the class' definition must be Lorentz-invariant. The physical field states automatically inherit entropy area laws from the PEPS class, and are fully described by the dissipative dynamics of a lower dimensional virtual field system. Our results lie at the intersection many-body physics, quantum field theory and quantum information theory, and facilitate future exchanges of ideas and insights between these disciplines.