Probing the diamagnetic term in light-matter interaction

Understand

We address the quantum estimation of the diamagnetic, or $A^2$, term in an effective model of light-matter interaction featuring two coupled oscillators.

• First, we calculate the quantum Fisher information of the diamagnetic parameter in the interacting ground state.
• Then, we find that typical measurements on the transverse radiation field, such as homodyne detection or photon counting, permit to estimate the diamagnetic coupling constant with near-optimal efficiency in a wide range of model parameters.
• Should the model admit a critical point, we also find that both measurements would become asymptotically optimal in its vicinity.