Stabilization of product states and excited-state quantum phase transitions in a coupled qubit-field system

Abstract

We study a system of a single qubit (or a few qubits) interacting with a soft-mode bosonic field. Considering an extended version of the Rabi model with both parity-conserving and parity-violating interactions, we disclose a complex arrangement of quantum phase transitions in the ground- and excited-state domains. An experimentally testable signature of some of these transitions is a dynamical stabilization of a fully factorized qubit-field state involving the field vacuum. It happens in the ultrastrong coupling regime where the superradiant field equilibrium is far from the vacuum state. The degree of stabilization varies abruptly with interaction parameters and increases with the softness of the field mode. We analyze semiclassical origins of these effects and show their connection to various forms of excited-state quantum phase transitions.

16 pages, 9 figures

References in corpus (17)

• Beyond the Jaynes-Cummings model: circuit QED in the ultrastrong coupling regime
• Observation of the Bloch-Siegert Shift in a Qubit-Oscillator System in the Ultrastrong Coupling Regime
• Excited state quantum phase transitions in many-body systems
• Observation of a quantum phase transition in the quantum Rabi model with a single trapped ion
• Excited-state quantum phase transitions
• Observation of Dynamical Quantum Phase Transition with Correspondence in Excited State Phase Diagram
• Spin-motion entanglement and state diagnosis with squeezed oscillator wavepackets
• Impact of Quantum Phase Transitions on Excited Level Dynamics
• Excited-state quantum phase transition in the Rabi model
• A robust scheme for the implementation of the quantum Rabi model in trapped ions
• Excited-state quantum phase transitions in systems with two degrees of freedom: III. Interacting boson systems
• Excited-state quantum phase transitions in spinor Bose-Einstein condensates
• Unconditional preparation of squeezed vacuum from Rabi interactions
• Dynamical preparation of stripe states in spin-orbit coupled gases
• Quasiclassical approach to quantum quench dynamics in the presence of an excited-state quantum phase transition
• Deterministic nonlinear gates with oscillators mediated by a qubit
• Continuum analogues of excited-state quantum phase transitions