Usage¶

User needs to have a valid LEXIS Platform project with allocated VLQ resources (quantum resources in general). How to get allocation to use the VLQ quantum machine located at IT4Innovations, VSB -- Technical university of Ostrava, follow the instructions in IT4I official documentation. How to request the access to the LEXIS Platform project is described in the IT4I documentation as well, or one can use the LEXIS Platform documentation.

Authentication¶

QaaS requires a valid LEXIS Platform access token. The recommended approach is automatic retrieval via py4lexis which handles user's authentication

from py4lexis.session import LexisSession

token: str = LexisSession().get_access_token()

Connecting to a backend¶

from qaas.client import QProvider
from qaas.client.backend_iqm import QBackendIQM

provider: QProvider = QProvider(
    lexis_project="LEXIS_PLATFORM_PROJECT_IDENTIFIER", token="USER_ACCESS_TOKEN"
)
backend: QBackendIQM = provider.get_backend(lexis_resource="QUANTUM_RESOURCE")

The lexis_resource string (e.g. "EU-XX-XXXX") maps to a specific quantum backend. Contact your LEXIS Platform project manager (PI of the LEXIS Platform project) for the resource name available to your project.

Inspecting hardware¶

print("Qubits:", backend.architecture.qubits)
print("Gates: ", list(backend.architecture.gates.keys()))

Circuit transpilation¶

Qiskit circuits must be transpiled for the IQM gate set before submission:

from qiskit import QuantumCircuit

qc: QuantumCircuit = QuantumCircuit(2, 2)
qc.h(0)
qc.cx(0, 1)
qc.measure_all()

qc_transpiled: QuantumCircuit = backend.transpile(qc, optimize_single_qubits=False)

optimize_single_qubits (default False) enables single-qubit gate merging. Leave it disabled unless you have verified that the optimisation is safe for your circuit.

Running a job¶

from qaas.client.backend_iqm import QJob

job: QJob = backend.run(qc_transpiled, shots=1000)

Retrieving results¶

from qiskit.result import Result

result: Result = job.result()
counts: dict[str, int] | list[dict[str, int]] = result.get_counts()

for bitstring, count in counts.items():
    if count > 0:
        print(f"|{bitstring}⟩: {count}")

Full example¶

from py4lexis.session import LexisSession
from qaas.client import QProvider
from qaas.client.backend_iqm import QBackendIQM, QJob
from qiskit import QuantumCircuit
from qiskit.result import Result

token: str = LexisSession().get_access_token()
provider: QProvider = QProvider(token, "LEXIS_PLATFORM_PROJECT_IDENTIFIER")
backend: QBackendIQM = provider.get_backend("QUANTUM_RESOURCE")

qc: QuantumCircuit = QuantumCircuit(2, 2)
qc.h(0)
qc.cx(0, 1)
qc.measure_all()

qc_transpiled: QuantumCircuit = backend.transpile(qc, optimize_single_qubits=False)
job: QJob = backend.run(qc_transpiled, shots=1000)
result: Result = job.result()
counts: dict[str, int] | list[dict[str, int]] = result.get_counts()

for state, count in counts.items():
    if count > 0:
        print(f"State '{state}': {count} counts")

Error handling¶

All QaaS errors are raised as QException:

from qaas.client import QProvider
from qaas.client.backend_iqm import QBackendIQM
from qaas.client.utils import QException
from qiskit.result import Result

try:
    provider: QProvider = QProvider(project, token)
    backend: QBackendIQM = provider.get_backend(resource)
    result: Result = backend.run(circuit, shots=1000).result()
except QException as e:
    print(f"QaaS error: {e}")

Common failure modes:

LEXIS Platform authentication failures (expired/invalid token)
Invalid LEXIS Platform project or quantum resource name
Backend connectivity issues
Circuit transpilation errors (unsupported gates)
Job execution failures (hardware unavailable)