Validity of the GGE for quantum quenches from interacting to noninteracting models

Understand

In the majority of the analytical verifications of the conjecture that the Generalised Gibbs Ensemble describes the large time asymptotics of local observables in quantum quench problems, both the post-quench and the pre-quench Hamiltonians are essentially noninteracting.

• We test this conjecture studying the field correlations in the more general case of an arbitrary pre-quench Hamiltonian, while keeping the post-quench one noninteracting.
• We first show that in the previously studied special case of a noninteracting pre-quench Hamiltonian, the validity of the conjecture is a consequence of Wick's theorem.
• We then show that it is also valid in the general case of an arbitrary interacting pre-quench Hamiltonian, but this time as a consequence of the cluster decomposition property of the initial state, which is a fundamental principle for generic physical states.