qml.add_decomps

add_decomps(op_type, *decomps)

Globally registers new decomposition rules with an operator class.

Note

This function is only relevant when the new experimental graph-based decomposition system (introduced in v0.41) is enabled via enable_graph(). This new way of doing decompositions is generally more resource efficient and accommodates multiple alternative decomposition rules for an operator. In this new system, custom decomposition rules are defined as quantum functions, and it is currently required that every decomposition rule declares its required resources using register_resources()

In the new system of decompositions, multiple decomposition rules can be registered for the same operator class. The specified decomposition rules in add_decomps serve as alternative decomposition rules that may be chosen if they lead to a more resource-efficient decomposition.

Parameters

• op_type – the operator type for which new decomposition rules are specified.

• decomps (DecompositionRule) – new decomposition rules to add to the given op_type. A decomposition is a quantum function registered with a resource estimate using qml.register_resources.

See also

register_resources() and list_decomps

Example

This example demonstrates adding two new decomposition rules to the qml.Hadamard operator.

import pennylane as qml
import numpy as np

@qml.register_resources({qml.RZ: 2, qml.RX: 1, qml.GlobalPhase: 1})
def my_hadamard1(wires):
    qml.RZ(np.pi / 2, wires=wires)
    qml.RX(np.pi / 2, wires=wires)
    qml.RZ(np.pi / 2, wires=wires)
    qml.GlobalPhase(-np.pi / 2, wires=wires)

@qml.register_resources({qml.RZ: 1, qml.RY: 1, qml.GlobalPhase: 1})
def my_hadamard2(wires):
    qml.RZ(np.pi, wires=wires)
    qml.RY(np.pi / 2, wires=wires)
    qml.GlobalPhase(-np.pi / 2)

qml.add_decomps(qml.Hadamard, my_hadamard1, my_hadamard2)

These two new decomposition rules for qml.Hadamard will be subsequently stored within the scope of this program, and they will be taken into account for all circuit decompositions for the duration of the session. To add alternative decompositions for a particular circuit as opposed to globally, use the alt_decomps argument of the decompose() transform.

See also

decompose()

code/api/pennylane.add_decomps

 

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