Entanglement detection in postquench nonequilibrium states: thermal Gibbs vs. generalized Gibbs ensemble

We use entanglement witnesses related to the entanglement negativity of the state to detect entanglement in the XY chain in the postquench states in the thermodynamic limit after a quench when the parameters of the Hamiltonian are changed suddenly. The entanglement negativity is related to correlations, which in the postquench stationary state are described by a generalized Gibbs ensemble, in the ideal case. If, however, integrability breaking perturbations are present, the system is expected to thermalize. Here, we compare the nearest-neighbor entanglement in the two circumstances.

Postquench states after a sudden quench protocol \((h_0, \gamma ) \rightarrow (h, \gamma )\) in the XY chain.