diamond_norm_distance

forest.benchmarking.distance_measures.diamond_norm_distance(choi0: numpy.ndarray, choi1: numpy.ndarray) → float

Return the diamond norm distance between two completely positive trace-preserving (CPTP) superoperators, represented as Choi matrices.

The calculation uses the simplified semidefinite program of Watrous in [CBN]

Note

This calculation becomes very slow for 4 or more qubits.

[CBN]

Semidefinite programs for completely bounded norms. J. Watrous. Theory of Computing 5, 11, pp. 217-238 (2009). http://theoryofcomputing.org/articles/v005a011 http://arxiv.org/abs/0901.4709

Parameters:

• choi0 – A 4**N by 4**N matrix (where N is the number of qubits)
• choi1 – A 4**N by 4**N matrix (where N is the number of qubits)