In mathematics, in the area of quantum information geometry, the Bures metric or Helstrom metric defines the infinitesimal distance between density matrix operators defining quantum states. It is a quantum generalization of the Fisher information metric, and is identical to the Fubini-Study metric (the Fubini-Study metric normally being written for pure states, not mixed states).
Read more about Bures Metric: Definition, Bures Distance, Quantum Fisher Information, Explicit Formulas, Two-Level System, See Also