The Reciprocal of the Mean Quantum Fisher Information per Particle in Generalized Two-Axis Twisting Model

We investigate the reciprocal of the mean quantum Fisher information per particle (RMQFI) in generalized two-axis twisting model; which generalizes the two-axis twisting model including a linear interaction controlled by an external field. In particular, we are interested in the dependence of RMQFI on the external field. By adopting frozen-spin approximation, we obtain the theoretical and numerical results for RMQFI, which is a periodical function. Except certain special conditions, the state is always entangled and the stronger external field induces to stronger entanglement and larger period of oscillation of RMQFI.