# cirq.kron_with_controls¶

cirq.kron_with_controls(*factors: Union[numpy.ndarray, complex, float]) → numpy.ndarray[source]

Computes the kronecker product of a sequence of values and control tags.

Use cirq.CONTROL_TAG to represent controls. Any entry of the output
corresponding to a situation where the control is not satisfied will
be overwritten by identity matrix elements.
The control logic works by imbuing NaN with the meaning “failed to meet one
or more controls”. The normal kronecker product then spreads the per-item
NaNs to all the entries in the product that need to be replaced by identity
matrix elements. This method rewrites those NaNs. Thus CONTROL_TAG can be
the matrix [[NaN, 0], [0, 1]] or equivalently [[NaN, NaN], [NaN, 1]].
Because this method re-interprets NaNs as control-failed elements, it won’t
propagate error-indicating NaNs from its input to its output in the way
you’d otherwise expect.

Examples

result = cirq.kron_with_controls(
cirq.CONTROL_TAG,
cirq.unitary(cirq.X))
print(result.astype(np.int32))

# prints:
# [[1 0 0 0]
#  [0 1 0 0]
#  [0 0 0 1]
#  [0 0 1 0]]

Parameters

*factors – The matrices, tensors, scalars, and/or control tags to combine together using np.kron.

Returns

The resulting matrix.