Circuit Complexity in Topological Quantum Field Theory

TL;DR

This paper introduces a novel approach to quantifying circuit complexity in Euclidean topological quantum field theories using pants decomposition, bridging concepts from quantum mechanics and topology.

Contribution

It proposes a new framework for defining circuit complexity in Euclidean TQFTs, diverging from traditional Lorentzian approaches, and applies pants decomposition to 2D bordisms.

Findings

Pants decomposition serves as a natural measure of circuit complexity in 2D TQFTs.

The formalism draws analogies with tensor networks and second quantization.

Provides a new perspective on complexity in Euclidean quantum field theories.

Abstract

Quantum circuit complexity has played a central role in recent advances in holography and many-body physics. Within quantum field theory, it has typically been studied in a Lorentzian (real-time) framework. In a departure from standard treatments, we aim to quantify the complexity of the Euclidean path integral. In this setting, there is no clear separation between space and time, and the notion of unitary evolution on a fixed Hilbert space no longer applies. As a proof of concept, we argue that the pants decomposition provides a natural notion of circuit complexity within the category of 2-dimensional bordisms and use it to formulate the circuit complexity of states and operators in 2-dimensional topological quantum field theory. We comment on analogies between our formalism and others in quantum mechanics, such as tensor networks and second quantization.