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Returns a list of matrices describing the channel for the given value.
cirq.protocols.channel(
val: Any,
default: Any = RaiseTypeErrorIfNotProvided
) -> Union[Tuple[np.ndarray, ...], TDefault]
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:
$$
\rho \rightarrow \sum_{k=0}^{r-1} A_k \rho A_k^\dagger
$$
These matrices are required to satisfy the trace preserving condition
$$
\sum_{k=0}^{r-1} A_k^\dagger A_k = I
$$
where $I$ is the identity matrix. The matrices $A_k$ are sometimes called Kraus or noise operators.
Args | |
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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 _mixture_ method
and its results is not NotImplement a tuple made up of channel
corresponding to that mixture being a probabilistic mixture of unitaries
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.
|