Collapse and revival of entanglement between qubits coupled to a spin coherent state

TL;DR

This paper explores how entanglement between two qubits evolves when they interact with a spin coherent state, revealing collapse and revival phenomena and effects of imperfections, relevant for quantum systems like superconducting circuits and ion traps.

Contribution

It extends the Jaynes-Cummings model by replacing the field mode with a composite spin, analyzing entanglement dynamics and imperfections in this new setup.

Findings

Collapse and revival of entanglement observed

Imperfections suppress coherent dynamics

Increasing mismatch width enhances decoherence

Abstract

We extend study of the Jaynes-Cummings model involving a pair of identical two-level atoms (or qubits) interacting with a single mode quantized field. We investigate the effects of replacing the radiation field mode with a composite spin, comprising $N$ qubits, or spin-1/2 particles. This model is relevant for physical implementations in superconducting circuit QED, ion trap and molecular systems. For the case of the composite spin prepared in a spin coherent state, we demonstrate the similarities of this set-up to the qubits-field model in terms of the time evolution, attractor states and in particular the collapse and revival of the entanglement between the two qubits. We extend our analysis by taking into account an effect due to qubit imperfections. We consider a difference (or `mismatch') in the dipole interaction strengths of the two qubits, for both the field mode and composite spin cases. To address decoherence due to this mismatch, we then average over this coupling strength difference with distributions of varying width. We demonstrate in both the field mode and the composite spin scenarios that increasing the width of the `error' distribution increases suppression of the coherent dynamics of the coupled system, including the collapse and revival of the entanglement between the qubits.