pauli_twirl_chi_matrix

forest.benchmarking.operator_tools.channel_approximation.pauli_twirl_chi_matrix(chi_matrix: numpy.ndarray) → numpy.ndarray

Implements a Pauli twirl of a chi matrix (aka a process matrix).

See [SPICC] for more details

[SPICC]Scalable protocol for identification of correctable codes. Silva et al. PRA 78, 012347 2008. http://dx.doi.org/10.1103/PhysRevA.78.012347 https://arxiv.org/abs/0710.1900

Note: Pauli twirling a quantum channel can give rise to a channel that is less noisy; use with care.

Parameters:chi_matrix – a dim**2 by dim**2 chi or process matrix
Returns:dim**2 by dim**2 chi or process matrix