Condition-number minimization for passive Fisher matrices

Determine the squeezing spectrum that minimizes the condition number of the passive Fisher matrix at fixed mean photon number.

Background

The paper establishes an E-optimal probe design that maximizes the smallest passive Fisher eigenvalue at fixed mean photon number. Along this family, however, the Fisher condition number grows with the photon budget, indicating an increasingly broad hierarchy between the largest and smallest sensitivities. The authors explicitly distinguish this objective from E-optimality and leave the fixed-resource condition-number minimization unresolved.