cirq.channel

cirq.channel(val: Any, default: Iterable[TDefault] = (array([], dtype=float64), )) → Union[Tuple[numpy.ndarray], Iterable[TDefault]]

Returns a list of matrices describing the channel for the given value.

These matrices are the terms in the operator sum representation of
a quantum channel. If the returned matrices are {A_0,A_1,..., A_{r-1}},
then this describes the channel:

ho -> \sum_{k=0}^{r-1} A_0

ho A_0^\dagger

These matrices are required to satisfy the trace preserving condition

\sum_{k=0}^{r-1} A_i^\dagger A_i = I

where I is the identity matrix. The matrices A_i are sometimes called

Krauss or noise operators.

Args:
    val: The value to describe by a channel.
    default: Determines the fallback behavior when `val` doesn't have
        a channel. If `default` is not set, a TypeError is raised. If
        default is set to a value, that value is returned.

Returns:
    If `val` has a _channel_ method and its result is not NotImplemented,
    that result is returned. Otherwise, if `val` has a _unitary_ method and
    its result is not NotImplemented a tuple made up of that result is
    returned. Otherwise, if a default value was specified, the default
    value is returned.

Raises:
    TypeError: `val` doesn't have a _channel_ or _unitary_ method (or that
        method returned NotImplemented) and also no default value was
        specified.