Ladder of Loschmidt anomalies in the deep strong-coupling regime of a qubit-oscillator system

Abstract

We uncover a remarkably regular array of singularity-like structures within the deep strongcoupling limit of qubit-oscillator (e.g. light-matter) systems described by the quantum Rabi model, as a function of time and coupling strength. These non-analytic anomalies in the Loschmidt amplitude (echoes) suggest the existence of new forms of dynamical phase transition within this deep strong-coupling regime. The key feature whereby the initial state collapses into orthogonal states at select values of the interaction strength and select times, may be used to enhance -or attackquantum information processing or computation schemes that rely on removing -or retaining -a given quantum state.