Decomposes a value into operations on the given qubits.

This method is used when decomposing gates, which don't know which qubits they are being applied to unless told. It decomposes the gate exactly once, instead of decomposing it and then continuing to decomposing the decomposed operations recursively until some criteria is met.

val The value to call ._decompose_(qubits) on, if possible.
qubits The value to pass into the named qubits parameter of val._decompose_.
default A default result to use if the value doesn't have a _decompose_ method or that method returns NotImplemented or None. If not specified, non-decomposable values cause a TypeError.
flatten If True, the returned OP-TREE will be flattened to a list of operations.
context Decomposition context specifying common configurable options for controlling the behavior of decompose.

The result of val._decompose_(qubits), if val has a _decompose_ method and it didn't return NotImplemented or None. Otherwise default is returned, if it was specified. Otherwise an error is raised.

val didn't have a _decompose_ method (or that method returned NotImplemented or None) and default wasn't set.