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catalyst.passes.ppm_compilation

ppm_compilation(qnode=None, *, decompose_method='pauli-corrected', avoid_y_measure=False, max_pauli_size=0)[source]

A quantum compilation pass that transforms Clifford+T gates into Pauli product measurements (PPMs).

Note

For improved integration with the PennyLane frontend, including inspectability with pennylane.specs(), please use pennylane.transforms.ppm_compilation().

This pass combines multiple sub-passes:

The avoid_y_measure and decompose_method arguments are passed to the ppr_to_ppm() pass. The max_pauli_size argument is passed to the commute_ppr() and merge_ppr_ppm() passes.

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

Parameters:

  • qnode (QNode, optional) – QNode to apply the pass to. If None, returns a decorator.

  • decompose_method (str, optional) – The method to use for decomposing non-Clifford PPRs. Options are "pauli-corrected", "auto-corrected" and "clifford-corrected". Defaults to "pauli-corrected". "pauli-corrected" uses a reactive measurement for correction. "auto-corrected" uses an additional measurement for correction. "clifford-corrected" uses a Clifford rotation for correction.

  • avoid_y_measure (bool) – Rather than performing a Pauli-Y measurement for Clifford rotations (sometimes more costly), a \(Y\) state (\(Y\vert 0 \rangle\)) is used instead (requires \(Y\) state preparation). Defaults to False.

  • max_pauli_size (int) – The maximum size of the Pauli strings after commuting or merging. Defaults to 0 (no limit).

Returns:

QNode

Example

If a merging resulted in a PPM acting on more than max_pauli_size qubits (here, max_pauli_size = 2), that merging would be skipped. However, when decomposed into PPMs, at least one qubit will be applied, so the final PPMs will act on at least one additional qubit.

import pennylane as qml
import catalyst

p = [("my_pipe", ["quantum-compilation-stage"])]
method = "clifford-corrected"

@qml.qjit(pipelines=p, target="mlir")
@catalyst.passes.ppm_compilation(decompose_method=method, max_pauli_size=2)
@qml.qnode(qml.device("null.qubit", wires=2))
def circuit():
    qml.CNOT([0, 1])
    qml.CNOT([1, 0])
    qml.adjoint(qml.T)(0)
    qml.T(1)
    return catalyst.measure(0), catalyst.measure(1)

print(circuit.mlir_opt)

Because Catalyst does not currently support execution of Pauli-based computation operations, we must halt the pipeline after quantum-compilation-stage. This ensures that only the quantum passes will be applied to the initial MLIR, without attempting to further compile for execution.

Example MLIR Representation:

. . .
%3 = qec.fabricate  magic : !quantum.bit
%mres, %out_qubits:3 = qec.ppm ["Z", "Z", "Z"] %1, %2, %3 : i1, !quantum.bit, !quantum.bit, !quantum.bit
%4 = quantum.alloc_qb : !quantum.bit
%mres_0, %out_qubits_1:3 = qec.ppm ["Z", "Z", "Y"](-1) %out_qubits#0, %out_qubits#1, %4 cond(%mres) : i1, !quantum.bit, !quantum.bit, !quantum.bit
%mres_2, %out_qubits_3 = qec.ppm ["X"] %out_qubits_1#2 cond(%mres) : i1, !quantum.bit
%5 = arith.xori %mres_0, %mres_2 : i1
%6:2 = qec.ppr ["Z", "Z"](2) %out_qubits_1#0, %out_qubits_1#1 cond(%5) : !quantum.bit, !quantum.bit
quantum.dealloc_qb %out_qubits_3 : !quantum.bit
%mres_4, %out_qubits_5 = qec.ppm ["X"] %out_qubits#2 : i1, !quantum.bit
%7:2 = qec.ppr ["Z", "Z"](2) %6#0, %6#1 cond(%mres_4) : !quantum.bit, !quantum.bit
quantum.dealloc_qb %out_qubits_5 : !quantum.bit
%8 = qec.fabricate  magic_conj : !quantum.bit
%mres_6, %out_qubits_7:2 = qec.ppm ["Z", "Z"] %7#1, %8 : i1, !quantum.bit, !quantum.bit
%9 = quantum.alloc_qb : !quantum.bit
%mres_8, %out_qubits_9:2 = qec.ppm ["Z", "Y"](-1) %out_qubits_7#0, %9 cond(%mres_6) : i1, !quantum.bit, !quantum.bit
%mres_10, %out_qubits_11 = qec.ppm ["X"] %out_qubits_9#1 cond(%mres_6) : i1, !quantum.bit
%10 = arith.xori %mres_8, %mres_10 : i1
%11 = qec.ppr ["Z"](2) %out_qubits_9#0 cond(%10) : !quantum.bit
quantum.dealloc_qb %out_qubits_11 : !quantum.bit
%mres_12, %out_qubits_13 = qec.ppm ["X"] %out_qubits_7#1 : i1, !quantum.bit
%12 = qec.ppr ["Z"](2) %11 cond(%mres_12) : !quantum.bit
quantum.dealloc_qb %out_qubits_13 : !quantum.bit
%mres_14, %out_qubits_15:2 = qec.ppm ["Z", "Z"] %7#0, %12 : i1, !quantum.bit, !quantum.bit
%mres_16, %out_qubits_17 = qec.ppm ["Z"] %out_qubits_15#1 : i1, !quantum.bit
. . .
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