Entangling operations in nonlinear two-atom Tavis-Cummings models

TL;DR

This paper derives an analytical solution for a nonlinear two-atom Tavis-Cummings model, enabling the study of entanglement dynamics and the implementation of entangling operations, including Bell measurements and three-qubit gates, in various physical systems.

Contribution

It provides a new analytical approach to analyze entanglement and implement quantum gates in nonlinear matter-field interaction models, including ion-trap systems.

Findings

Analytical expressions for atomic concurrence and purity.

Implementation of Bell measurements through field measurement.

Proposal of a three-qubit gate generating GHZ and W states.

Abstract

We derive an analytical approximate solution of the time-dependent state vector in terms of material Bell states and coherent states of the field for a generalized two-atom Tavis-Cummings model with nonlinear intensity dependent matter-field interaction. Using this solution, we obtain simple expressions for the atomic concurrence and purity in order to study the entanglement in the system at specific interaction times. We show how to implement entangling atomic operations through measurement of the field. We illustrate how these operations can lead to a complete Bell measurement. Furthermore, when considering two orthogonal states of the field as levels of a third qubit, it is possible to implement a unitary three-qubit gate capable of generating authentic tripartite entangled states such as the Greenberger-Horne-Zeilinger (GHZ) state and the W-state. As an example of the generic model, we present an ion-trap setting employing the quantized mode of the center of mass motion instead of the photonic field, showing that the implementation of realistic entangling operations from intrinsic nonlinear matter-field interactions is indeed possible.