catalyst.passes.merge_rotations

merge_rotations(fn=None)

Specify that the -merge-rotations MLIR compiler pass for merging roations (peephole) will be applied.

The full list of supported gates are as follows:

qml.RX, qml.CRX, qml.RY, qml.CRY, qml.RZ, qml.CRZ, qml.PhaseShift, qml.ControlledPhaseShift, qml.MultiRZ.

Note

Unlike PennyLane circuit transformations, the QNode itself will not be changed or transformed by applying these decorators.

As a result, circuit inspection tools such as draw() will continue to display the circuit as written in Python.

To instead view the optimized circuit, the MLIR must be viewed after the "QuantumCompilationPass" stage via the get_compilation_stage() function.

Parameters

fn (QNode) – the QNode to apply the cancel inverses compiler pass to

Return type

QNode

Example

In this example the three qml.RX will be merged in a single one with the sum of angles as parameter.

from catalyst.debug import get_compilation_stage
from catalyst.passes import merge_rotations

dev = qml.device("lightning.qubit", wires=1)

@qjit(keep_intermediate=True)
@merge_rotations
@qml.qnode(dev)
def circuit(x: float):
    qml.RX(x, wires=0)
    qml.RX(0.1, wires=0)
    qml.RX(x**2, wires=0)
    return qml.expval(qml.PauliZ(0))

>>> circuit(0.54)
Array(0.5965506257017892, dtype=float64)

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