Comment on "Extension of the adiabatic theorem"

TL;DR

This paper challenges a previous conjecture about quantum quenches, providing a counterexample that shows the overlap between initial and postquench states is not always maximal for the ground state.

Contribution

It presents a specific counterexample in free-fermion systems that disproves the conjecture for quantum quenches within the same phase.

Findings

Counterexample in free-fermion systems disproves the conjecture

Overlap is not always maximal for the postquench ground state

Conjecture does not hold in general for quantum quenches within the same phase

Abstract

Phys. Rev. B 113, 165102 (2026) proposed the conjecture that, for quantum quenches within the same phase, the overlap between the initial ground state and postquench eigenstates is maximal for the postquench ground state. We show that this conjecture is not valid in general. An explicit local, translationally invariant, gapped free-fermion counterexample exists even though the pre- and postquench Hamiltonians are connected by a symmetry-preserving gapped path and the thermodynamic-limit spectrum is continuous.