qml.capture.expand_plxpr_transforms

expand_plxpr_transforms(f)

Function for applying transforms to plxpr.

Currently, when program capture is enabled, transforms are used as higher-order primitives. These primitives are present in the program, but their respective transform is not applied when a transformed function is called. expand_plxpr_transforms further “transforms” the input function to apply any transform primitives that are present in the program being run.

Example

In the below example, we can see that the qml.transforms.cancel_inverses transform has been applied to a function. However, the resulting program representation leaves the cancel_inverses transform as a primitive without actually transforming the program.

qml.capture.enable()

@qml.transforms.cancel_inverses
def circuit():
    qml.X(0)
    qml.S(1)
    qml.X(0)
    qml.adjoint(qml.S(1))
    return qml.expval(qml.Z(1))

>>> qml.capture.make_plxpr(circuit)()
{ lambda ; . let
    a:AbstractMeasurement(n_wires=None) = cancel_inverses_transform[
    args_slice=slice(0, 0, None)
    consts_slice=slice(0, 0, None)
    inner_jaxpr={ lambda ; . let
        _:AbstractOperator() = PauliX[n_wires=1] 0
        _:AbstractOperator() = S[n_wires=1] 1
        _:AbstractOperator() = PauliX[n_wires=1] 0
        b:AbstractOperator() = S[n_wires=1] 1
        _:AbstractOperator() = Adjoint b
        c:AbstractOperator() = PauliZ[n_wires=1] 1
        d:AbstractMeasurement(n_wires=None) = expval_obs c
      in (d,) }
    targs_slice=slice(0, None, None)
    tkwargs={}
    ]
  in (a,) }

To apply the transform, we can use expand_plxpr_transforms as follows:

>>> transformed_circuit = qml.capture.expand_plxpr_transforms(circuit)
>>> qml.capture.make_plxpr(transformed_circuit)()
{ lambda ; . let
    a:AbstractOperator() = PauliZ[n_wires=1] 1
    b:AbstractMeasurement(n_wires=None) = expval_obs a
  in (b,) }

As seen, the transform primitive is no longer present, but it has been applied to the original program, indicated by the inverse operators being cancelled.

Parameters

f (Callable) – The callable to which any present transforms should be applied.

Returns

Callable with transforms applied.

Return type

Callable

code/api/pennylane.capture.expand_plxpr_transforms

 

Download Python script

 

Download Notebook

 

View on GitHub