vectorize

vectorize(density_matrix, method='col')

Flatten an operator to a vector in a specified basis.

Parameters

• density_matrix (ndarray) – a density matrix.

• method (str) –

  the method of vectorization. Allowed values are:

  • ’col’ (default) flattens to column-major vector.

  • ’row’ flattens to row-major vector.

  • ’pauli’ flattens in the n-qubit Pauli basis.

  • ’pauli-weights’: flattens in the n-qubit Pauli basis ordered by

    weight.

Returns

the resulting vector.

Return type

ndarray

Raises

Exception – if input state is not a n-qubit state