Generating Circuit using BQSKit

[manu123416]

Hi, I am trying to generate to quantum circuit using BQSKit. I want to generate circuit for 4, 6, and 8 qubits. Do you think, that the below approach can generate circuit quickly or do not I need to add some other passes?
I am ok even if circuit generated has a less precision. Thank you.

from bqskit.compiler import Compiler
from bqskit.ext import bqskit_to_qiskit
from bqskit.qis import UnitaryMatrix
from bqskit.ir import Circuit
from bqskit.passes import (
    QuickPartitioner,
    QSearchSynthesisPass,
    LEAPSynthesisPass,
    QFASTDecompositionPass,
    SetModelPass
)
from bqskit.compiler.machine import MachineModel
from bqskit.qis.graph import CouplingGraph

def bqskit_unitary_method(num_qubits, U_inv, qc):
    model = MachineModel(
        num_qudits=num_qubits,
        coupling_graph=CouplingGraph.all_to_all(num_qubits)
    )
    
    # Configure workflow based on qubit count
    if num_qubits <= 4:
        workflow = [
            SetModelPass(model),
            QSearchSynthesisPass(instantiate_options={
                'max_workers': 42,  # Use all cores
                'multistarts': 84   # Hyperthreading optimization
            })
        ]
    elif num_qubits <= 6:
        workflow = [
            SetModelPass(model),
            LEAPSynthesisPass(instantiate_options={
                'max_workers': 42,
                'min_iters': 5,
                'max_iters': 50
            })
        ]
    else:
        workflow = [
            QuickPartitioner(block_size=4),
            QFASTDecompositionPass(),
            SetModelPass(model),
            QSearchSynthesisPass(instantiate_options={'max_workers': 42})
        ]

    circuit_to_compile = Circuit.from_unitary(U_inv)
    compiler_instance = Compiler()
    generated_circuit = compiler_instance.compile(circuit_to_compile, workflow)

[edyounis]

Moving this to a discussion.

[edyounis]

The high-level idea here is good. Some technical changes are necessary tho:

• max_workers is not an instantiate option. There will be no errors. It will just not do anything. To set worker count, you set the num_workers parameter on the Compiler constructor. By default, this will use all logical threads, which will account for hyperthreading.
• I would be cautious using qsearch for 4-qubit circuits. If you expect them to be shallow, then it will be okay. Otherwise, leap is better for 4.
• 84 multistarts is also extreme; 8 would be a good starting point. Multistarts refer to how many times each candidate circuit is instantiated (with a different initial starting parameter guess) during the search. But, multiple candidate circuits are evaluated in parallel as well.
• Min and max iters is not an instantiate option for LEAP in the default configuration. If you use Qfactor as an instantiator (not recommended here), these are valid options. Instead, you should also set multistarts here. I would be more careful with multistarts for the 6-qubit run since higher numbers multiply the runtime.
• For the QFAST workflow, you will need to wrap the QSearch last step in a ForEachBlock clause. See how it's done in the QFAST example for reference.