Getting started#

Installation#

For installation a UNIX-like system is currently needed due to PyMetis being used for automatic cut finding. On Windows use WSL.

Pip#

Installation should be done via uv:

uv pip install QCut
#or
uv add QCut

If using other than the default Qiskit version (newest) it is recommended to install Qiskit first before installing QCut.

QCut does not install a simulator. The examples run on Qiskit Aer, which needs uv pip install qiskit-aer. For drawing circuits you might also need uv pip install pylatexenc.

uv itself can be installed with:

#Linux / mac
curl -LsSf https://astral.sh/uv/install.sh | sh

IQM hardware and fake backends#

QCut ships an extra for this, so the adapter comes with it:

uv pip install "QCut[iqm]"
#or
uv add "QCut[iqm]"

That installs IQM client with its Qiskit adapter, which covers Qiskit 1.0 up to but not including 2.2. Installing the extra will therefore hold Qiskit below 2.2, put it in an environment whose Qiskit is already in range if you would rather the resolver left it alone.

After installation just import the backend you want to use:

from iqm.qiskit_iqm import IQMFakeAdonis
backend = IQMFakeAdonis()

Install from source#

It is also possible to use QCut by cloning the repository and including it in your project folder:

cd QCut
uv pip install .
#or
uv sync --no-dev

#or with dev deps
uv sync

Quick start#

Mark where to cut, split the circuit, build the experiment for the observables wanted, run it, and put the expectation values back together:

import QCut as ck
from QCut import cut, cutGate
from qiskit import QuantumCircuit
from qiskit.circuit.library import CXGate
from qiskit_aer import AerSimulator

circuit = QuantumCircuit(5)
for qubit in range(5):
    circuit.ry(0.4 + 0.3 * qubit, qubit)
circuit.cx(0, 1)
circuit.append(**cutGate(CXGate(), 1, 2))  # a gate cut
circuit.cx(2, 3)
circuit.append(cut(), [3])  # a wire cut
circuit.cx(3, 4)

observables = ["IIIIZ", "IIZII", "ZZIII"]

cut_circuit = ck.get_locations_and_subcircuits(circuit)
# On a device with a coupling map, transpile the subcircuits for it here:
# cut_circuit = ck.transpile_subcircuits(cut_circuit, backend)
experiment = ck.get_experiment_circuits(cut_circuit, observables)

job = ck.submit_experiments(experiment, backend=AerSimulator(), shots=4096)
print(ck.estimate_expectation_values(job.result()))

[0.9204 0.3866 -0.0315]

against exact values of [0.9211 0.3806 -0.0292] for the uncut circuit.

User guide goes through each step, Primitives runs several cut circuits in one call, and Options lists what can be configured.

Getting started

Contents