Feature: Bures angle

[vprusso]

Calculate the Bures angle is a measure of distance between two quantum states [1].

The Bures angle can be computed as follows:

def bures_angle(rho: np.ndarray, sigma: np.ndarray) -> float:
    """Returns the Bures angle between two density operators."""
    return np.real(np.arccos(np.sqrt(fidelity(rho, sigma))))

As this is a metric, the location for this should be in state_metrics/bures_angle.py. Ensure that proper tests in tests/test_state_metrics/test_bures_angle.py and documentation in docs/state_metrics.rst are included.

[1]: Wikipedia: Bures angle

[epelaaez]

Hey! Are you looking for people to work on this?

[vprusso]

Hi @epelaaez. Yes, by all means, if you'd like to go ahead and attempt this issue, by all means!

Thank you for your interest in toqito, and if you enjoy the project, give it a star and let me know if I can help out with using or contributing! Cheers!