catalyst.passes.t_layer_reduction¶

t_layer_reduction(qnode)[source]¶

Specify that the``–t-layer-reduction`` MLIR compiler pass, which reduces the depth and count of non-Clifford PPRs by commuting adjacent PPRs and merging compatible ones. For details, see the Figure 6 of [A Game of Surface Code](https://arXiv:1808.02892v3) paper.

A layer is a set of PPRs that mutually commute or act on disjoint qubits.

Parameters:: fn (QNode) – QNode to apply the pass to.
Returns:: Returns decorated QNode.
Return type:: QNode

Example

In example below, after performing the to_ppr to merge_ppr_ppm passes, the circuit contains a four depth of Non-Clifford PPRs. The t_layer_reduction pass move the PPR(“X”) on qubit Q1 to first layer, which results in a three depth of Non-Clifford PPRs.

In the example below, after applying the to_ppr, commute_ppr, and merge_ppr_ppm passes, the circuit has four layers of non-Clifford PPRs. The t_layer_reduction pass moves the PPR(“X”) on qubit 1 into the first layer, reducing the non-Clifford depth from four to three.

import pennylane as qml
from catalyst import qjit, measure
from catalyst.passes import to_ppr, commute_ppr, t_layer_reduction, merge_ppr_ppm

pips = [("pipe", ["enforce-runtime-invariants-pipeline"])]


@qjit(pipelines=pips, target="mlir")
@t_layer_reduction
@merge_ppr_ppm
@commute_ppr
@to_ppr
@qml.qnode(qml.device("null.qubit", wires=3))
def circuit():
    n = 3
    for i in range(n):
        qml.H(wires=i)
        qml.S(wires=i)
        qml.CNOT(wires=[i, (i + 1) % n])
        qml.T(wires=i)
        qml.H(wires=i)
        qml.T(wires=i)

    return [measure(wires=i) for i in range(n)]


print(circuit.mlir_opt)

catalyst.passes.t_layer_reduction¶

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