qp.transforms.disentangle_cnot

disentangle_cnot()

A peephole optimization for replacing CNOT gates with single-qubit gates.

Note

This transform requires decorating the workflow with qjit().

Parameters:

fn (QNode) – the QNode to apply the pass to

Returns:

QNode

Example

In the circuit below, the CNOT gate can be simplified to just a PauliX gate since the control qubit is always in the \(|1\rangle\) state.

import pennylane as qp

dev = qp.device("lightning.qubit", wires=2)

@qp.qjit(capture=True)
@qp.transforms.disentangle_cnot
@qp.qnode(dev)
def circuit():
    # first qubit in |1>
    qp.X(0)
    # second qubit in |0>
    # current state : |10>
    qp.CNOT([0, 1]) # state after CNOT : |11>
    return qp.state()

When inspecting the circuit resources, only PauliX gates are present.

>>> print(qp.specs(circuit, level=1)())
Device: lightning.qubit
Device wires: 2
Shots: Shots(total=None)
Level: disentangle-cnot

Wire allocations: 2
Total gates: 2
Gate counts:
- PauliX: 2
Measurements:
- state(all wires): 1
Depth: Not computed

code/api/pennylane.transforms.disentangle_cnot

 

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