qml.transforms.merge_ppr_ppm¶

merge_ppr_ppm(tape=None, *, max_pauli_size=0)[source]¶

A quantum compilation pass that absorbs Clifford Pauli product rotation (PPR) operations, \(\exp{-iP\tfrac{\pi}{4}}\), into the final Pauli product measurements (PPMs).

Note

This transform requires decorating the workflow with @qml.qjit. In addition, the circuits generated by this pass are currently not executable on any backend. This pass is only for Pauli-based-computation analysis with the null.qubit device and potential future execution when a suitable backend is available.

Secondly, the merge_ppr_ppm transform does not currently affect terminal measurements. So, for accurate results, it is recommended to return nothing (i.e., a blank return statement) from the QNode.

Lastly, the pennylane.transforms.to_ppr() transform must be applied before merge_ppr_ppm.

For more information on PPRs and PPMs, check out the Compilation Hub.

Parameters:

fn (QNode) – QNode to apply the pass to
max_pauli_size (int) – The maximum size of Pauli strings resulting from merging. If a merge results in a PPM that acts on more than max_pauli_size qubits, that merge will not be performed. The default value is 0 (no limit).

Returns:

QNode

Note

For better compatibility with other PennyLane functionality, ensure that PennyLane program capture is enabled with pennylane.capture.enable().

Example

The merge_ppr_ppm compilation pass can be applied as a decorator on a QNode:

import pennylane as qml
import jax.numpy as jnp

qml.capture.enable()

@qml.qjit(target="mlir")
@qml.transforms.merge_ppr_ppm(max_pauli_size=2)
@qml.transforms.to_ppr
@qml.qnode(qml.device("null.qubit", wires=2))
def circuit():
    qml.PauliRot(jnp.pi / 2, pauli_word="Z", wires=0)
    qml.PauliRot(jnp.pi / 2, pauli_word="X", wires=1)

    ppm = qml.pauli_measure(pauli_word="ZX", wires=[0, 1])

    return

To inspect programs compiled with merge_ppr_ppm via specs(), ensure that target="mlir" is given in the qjit decorator.

>>> print(qml.specs(circuit, level=3)())
Device: null.qubit
Device wires: 2
Shots: Shots(total=None)
Level: 3

Resource specifications:
    Total wire allocations: 2
    Total gates: 1
    Circuit depth: Not computed

Gate types:
    PPM: 1

Measurements:
    No measurements.

If a merging resulted in a PPM acting on more than max_pauli_size qubits, that merging operation would be skipped.

code/api/pennylane.transforms.merge_ppr_ppm

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qml.transforms.merge_ppr_ppm¶

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