Entanglement evolution after connecting finite to infinite quantum chains

TL;DR

This paper investigates how entanglement entropy evolves over time when finite quantum chains are connected to infinite chains, revealing universal behaviors and conformal field theory predictions in critical systems.

Contribution

It provides the first detailed analysis of entanglement dynamics after connecting finite and infinite quantum chains, including verification of conformal field theory predictions.

Findings

Entanglement entropy increases after connection, then slowly decays.

Conformal field theory accurately predicts early-time behavior in critical systems.

A step structure appears in entanglement at late times.

Abstract

We study zero-temperature XX chains and transverse Ising chains and join an initially separate finite piece on one or on both sides to an infinite remainder. In both critical and non-critical systems we find a typical increase of the entanglement entropy after the quench, followed by a slow decay towards the value of the homogeneous chain. In the critical case, the predictions of conformal field theory are verified for the first phase of the evolution, while at late times a step structure can be observed.