Entanglement storage by classical fixed points in the two-axis countertwisting model

TL;DR

This paper investigates a method to store entanglement in the two-axis countertwisting model by leveraging stable fixed points, with analysis of noise effects and optimal state manipulation for quantum information applications.

Contribution

It introduces a scheme for entanglement storage using fixed points in the two-axis countertwisting model, combining dynamical generation and stabilization of entangled states.

Findings

Entanglement can be generated from initial states near unstable saddle points.

Optimal timing and rotation can freeze the entangled state's properties.

Noise effects are often weak due to parity conservation.

Abstract

We analyze a scheme for storage of entanglement quantified by the quantum Fisher information in the two-axis countertwisting model. A characteristic feature of the two-axis countertwisting Hamiltonian is the existence of the four stable center and two unstable saddle fixed points in the mean-field phase portrait. The entangled state is generated dynamically from an initial spin coherent state located around an unstable saddle fixed point. At an optimal moment of time the state is shifted to a position around stable center fixed points by a single rotation, where its dynamics and properties are approximately frozen. We also discuss evolution with noise. In some cases the effect of noise turns out to be relatively weak, which is explained by parity conservation.