def aschannel(self) -> 'Channel':
"""Converts a Gate into a Channel"""
N = self.qubit_nb
R = 4
tensor = bk.outer(self.tensor, self.H.tensor)
tensor = bk.reshape(tensor, [2**N] * R)
tensor = bk.transpose(tensor, [0, 3, 1, 2])
return Channel(tensor, self.qubits)
def sharp(self) -> 'Channel':
r"""Return the 'sharp' transpose of the superoperator.
The transpose :math:`S^\#` switches the two covariant (bra)
indices of the superoperator. (Which in our representation
are the 2nd and 3rd super-indices)
If :math:`S^\#` is Hermitian, then :math:`S` is a Hermitian-map
(i.e. transforms Hermitian operators to hJrmitian operators)
Flattening the :math:`S^\#` superoperator to a matrix gives
the Choi matrix representation. (See channel.choi())
"""
N = self.qubit_nb
tensor = self.tensor
tensor = bk.reshape(tensor, [2**N] * 4)
tensor = bk.transpose(tensor, (0, 2, 1, 3))
tensor = bk.reshape(tensor, [2] * 4 * N)
return Channel(tensor, self.qubits)