Entanglement evolution after connecting finite to infinite quantum chains

Understand

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.