bures_angle

forest.benchmarking.distance_measures.bures_angle(rho: numpy.ndarray, sigma: numpy.ndarray) → float

Computes the Bures angle (AKA Bures arc or Bures length) between two states rho and sigma:

\[D_A(\rho, \sigma) = \arccos(\sqrt{F(\rho, \sigma)})\]

where \(F(\rho, \sigma)\) is the fidelity.

The Bures angle is a measure of statistical distance between quantum states.

Parameters:

• rho – Is a dim by dim positive matrix with unit trace.
• sigma – Is a dim by dim positive matrix with unit trace.

Returns:

Bures angle which is a scalar.