mppovm.py 文件源码

def pauli_mpp(nr_sites, local_dim):
    r"""Pauli POVM tensor product as MP-POVM

    The resulting MP-POVM will contain all tensor products of the
    elements of the local Pauli POVM from :func:`mpp.pauli_povm()`.

    :param int nr_sites: Number of sites of the returned MP-POVM
    :param int local_dim: Local dimension
    :rtype: MPPovm

    For example, for two qubits the `(1, 3)` measurement outcome is
    `minus X` on the first and `minus Y` on the second qubit:

    >>> nr_sites = 2
    >>> local_dim = 2
    >>> pauli = pauli_mpp(nr_sites, local_dim)
    >>> xy = np.kron([1, -1], [1, -1j]) / 2
    >>> xyproj = np.outer(xy, xy.conj())
    >>> proj = pauli.get([1, 3], astype=mp.MPArray) \
    ...             .to_array_global().reshape((4, 4))
    >>> abs(proj - xyproj / 3**nr_sites).max() <= 1e-10
    True

    The prefactor `1 / 3**nr_sites` arises because X, Y and Z are in a
    single POVM.

    """
    from mpnum.povm import pauli_povm
    return MPPovm.from_local_povm(pauli_povm(local_dim), nr_sites)