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Usage

Authentication

QaaS requires a valid LEXIS access token. The recommended approach is automatic retrieval via py4lexis:

from py4lexis.session import LexisSession

token = LexisSession().get_access_token()

token = "your_lexis_access_token"

Connecting to a backend

from qaas import QProvider

provider = QProvider(token, project_name="my_lexis_project")
backend  = provider.get_backend("EQE1-CZ-P0001")

The resource_name string (e.g. "EQE1-CZ-P0001") maps to a specific quantum backend. Contact your LEXIS project manager 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(2, 2)
qc.h(0)
qc.cx(0, 1)
qc.measure_all()

qc_transpiled = 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

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

Retrieving results

result = job.result()
counts = 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 import QProvider
from qiskit import QuantumCircuit

token    = LexisSession().get_access_token()
provider = QProvider(token, "vlq_demo_project")
backend  = provider.get_backend("qaas_user")

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

job    = backend.run(backend.transpile(qc, optimize_single_qubits=False), shots=1000)
counts = job.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 import QProvider, QException

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

Common failure modes:

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