Troubleshooting¶

Authentication required¶

AuthenticationError: Authentication required. Provide a token or
client_id+client_secret (or OPENQUANTUM_TOKEN / OPENQUANTUM_CLIENT_ID +
OPENQUANTUM_CLIENT_SECRET / OPENQUANTUM_SDK_KEY).

No credentials were found. OpenQuantumSampler calls OpenQuantumClient.from_env(). Set OPENQUANTUM_CLIENT_ID and OPENQUANTUM_CLIENT_SECRET, set OPENQUANTUM_TOKEN or OPENQUANTUM_SDK_KEY, or pass token=, client_id= + client_secret=, or a pre-built client=. See Authentication.

`Circuit has no measurement gates`¶

CircuitValidationError: Circuit has no measurement gates; add cirq.measure(...)
before sampling on the Open Quantum platform.

The platform is shot-based and Cirq's QASM exporter does not add measurements. Append a measurement to your circuit:

circuit.append(cirq.measure(*cirq.LineQubit.range(2), key="m"))

`configuration_data validation failed: ... required property 'engine'`¶

The target backend requires extra configuration that was not supplied. The Quantum Rings simulator, for example, requires an engine:

sampler = OpenQuantumSampler(
    backend="qr:gpu-gb10",
    configuration_data={"engine": "amber_quantum_rings"},
)

`configuration_data validation failed: ... must match "else" schema`¶

A backend's configuration schema can be conditional. The Quantum Rings simulator only permits threshold when performance="CUSTOM". Send such fields only when they apply:

# Valid: no threshold unless performance is CUSTOM
configuration_data={"engine": "amber_quantum_rings"}

# Valid: threshold allowed because performance is CUSTOM
configuration_data={"engine": "amber_quantum_rings", "performance": "CUSTOM", "threshold": 128}

Results look bit-reversed¶

The platform returns counts little-endian (first classical bit rightmost), while Cirq is big-endian. The sampler reverses bitstrings by default (reverse_bits=True) so the mapping is correct. If a particular backend returns counts big-endian and your results look reversed, construct the sampler with reverse_bits=False. Confirm with an asymmetric state: apply X to one qubit and check which bit flips.

`to_qasm` raised on an unsupported gate¶

Cirq could not express an operation in OpenQASM. Decompose it before sampling:

circuit = cirq.Circuit(cirq.decompose(circuit))

Shots are required¶

Open Quantum is shot-based; analytic execution is not supported. Pass repetitions= to run / sample / run_sweep. For local state-vector simulation use cirq.Simulator instead.

Backend is offline or not accepting jobs¶

Pick another backend. List what is online with the Core SDK (client.backends(online=True)) or the Open Quantum Portal.

Organization could not be resolved¶

If your account belongs to more than one organization, pass an explicit organization_id to the sampler (discover it via client.organizations()).