qml.transforms.zx.reduce_non_clifford¶

reduce_non_clifford(tape)[source]¶

Reduce the number of non-Clifford gates by applying a combination of phase gadgetization strategies and Clifford gate simplification rules.

This transform performs the following simplification/optimization steps:

Apply the full_reduce simplification pipeline to the pyzx graph representation (see to_zx()) of the given input circuit.
Use the extract_circuit function to extract the equivalent sequence of gates and build a new optimized circuit.
Apply the basic_optimization pass to further optimize the phase-polynomial blocks in the circuit.

This pipeline does not run the Third Order Duplicate and Destroy (TODD) algorithm and thus is not restricted to Clifford + T circuits.

Note

The transformed output circuit is equivalent to the input up to a global phase.

Parameters:: tape (QNode or QuantumScript or Callable) – the input circuit to be transformed.
Returns:: the transformed circuit as described in qml.transform.
Return type:: qnode (QNode) or quantum function (Callable) or tuple[List[QuantumScript], function]
Raises:: ModuleNotFoundError – if the required pyzx package is not installed.

Example:

import pennylane as qml
import pennylane.transforms.zx as zx

dev = qml.device("default.qubit")

@zx.reduce_non_clifford
@qml.qnode(dev)
def circuit(x, y):
    qml.T(0)
    qml.Hadamard(0)
    qml.Hadamard(0)
    qml.CNOT([0, 1])
    qml.T(0)
    qml.RX(x, 1)
    qml.RX(y, 1)
    return qml.state()

>>> print(qml.draw(circuit)(3.2, -2.2))
0: ──S─╭●─────────────────┤  State
1: ────╰X──H──RZ(1.00)──H─┤  State

Note

This transform is designed to minimize non-Clifford phase gates (e.g. T, RZ), and is not as effective at reducing the number of two-qubit gates (e.g. CNOT). For example, you might see a substantial increase in CNOT gates when optimizing a circuit composed primarily of Toffoli gates. Conversely, it tends to perform quite well on Trotterized chemistry circuits.

For more details about ZX calculus-based simplification of quantum circuits, see the following papers:

Ross Duncan, Aleks Kissinger, Simon Perdrix, John van de Wetering (2019), “Graph-theoretic Simplification of Quantum Circuits with the ZX-calculus”, arXiv:1902.03178;
Aleks Kissinger, John van de Wetering (2020), “Reducing T-count with the ZX-calculus”, arXiv:1903.10477.

code/api/pennylane.transforms.zx.reduce_non_clifford

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qml.transforms.zx.reduce_non_clifford¶

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