Decoherence and energy flow in the sunburst quantum Ising model

Abstract

We study the post-quench unitary dynamics of a quantum sunburst spin model, composed of a transverse-field quantum Ising ring which is suddenly coupled to a set of independent external qubits along the longitudinal direction, in a way to respect a residual translation invariance and the Ising symmetry. Starting from the different equilibrium quantum phases of the system, we characterize the decoherence and the energy storage in the external qubits, which may be interpreted as a probing apparatus for the inner Ising ring. Our results show that, in proximity of the quantum transitions of the Ising ring, either first-order or continuous, it is possible to put forward dynamic finite-size scaling frameworks which unveil peculiar scaling regimes, depending on the way in which the large-size limit is taken: either by fixing the number n of probing qubits, or their interspace distance b. In any case, the dependence of the various observables on n can be reabsorbed into a redefinition of the quench parameter by a prefactor. We also address the role of a nearest-neighbor coupling between the external qubits.