Code example#

Initialising the IQM client is simple, and in case you perform authentication as described below, requires only the URL of the IQM quantum computer.

from iqm.iqm_client import IQMClient

server_url = "https://IQM_SERVER_URL"

iqm_client = IQMClient(server_url)

To submit a quantum circuit for execution, it has to be specified using the Circuit class. The available native instructions are documented in the Instruction class.

from iqm.iqm_client import Circuit, Instruction

instructions = (
    Instruction(
        name="prx", qubits=("QB1",), args={"phase_t": 0.7, "angle_t": 0.25}
    ),
    Instruction(name="cz", qubits=("QB1", "QB2"), args={}),
    Instruction(name="measure", qubits=("QB2",), args={"key": "Qubit 2"}),
)

circuit = Circuit(name="quantum_circuit", instructions=instructions)

Then the circuit can be submitted, and its status and result can be queried with the job id.

job_id = iqm_client.submit_circuits([circuit])

job_status = iqm_client.get_run_status(job_id)

job_result = iqm_client.wait_for_results(job_id)

A dict containing arbitrary metadata can be attached to the circuit before submitting it for execution. The attached metadata should consist only of values of JSON serializable datatypes. A utility function to_json_dict() can be used to convert supported datatypes, e.g. numpy.ndarray, to equivalent JSON serializable types.

The progress of the job can be followed with IQMClient.get_run_status(). Once the job is ready, the results can be read with IQMClient.get_run(). Both of these actions are combined in IQMClient.wait_for_results() which waits until the job is ready and then returns the result.

In addition to the actual results, job result contains also metadata of the job execution. The metadata includes the original request, ID of the calibration set used in the execution, and a collection of timestamps describing the duration of the execution.

Job phases and related timestamps#

The timestamps returned with job results are stored as an optional dict called timestamps in the metadata of RunResult of the job. Each timestamp is stored in the dict with a key describing the point in job processing where the timestamp was stored. For example, the timestamp stored at the start of circuit compilation step is stored with key compile_start. Other timestamps are stored in the same way, with keys containing the step name, compile, submit or execution, and either a _start or _end suffix. In addition, there are also timestamps for starting and ending the job itself, job_start and job_end. If the job processing is terminated before it is complete the timestamps of steps not processed will not be present in the dict.

The first timestamp stored is the job_start timestamp. It is stored when the server receives the job request.

The job processing starts with compilation step where the circuits are converted to pulse schedules that can be sent for execution. Compilation step produces timestamps compile_start and compile_end.

The pulse schedules are then submitted for execution. This step produces timestamps submit_start and submit_end.

After submitting the pulse schedules the server waits for the execution results. This step produces timestamps execution_start and execution_end.

Finally, when job processing is complete, regardless whether the job was successful or not, the timestamp job_end is stored.

Authentication#

IQM uses bearer token authentication to manage access to quantum computers. Currently, there are three mutually exclusive ways of providing an authentication token to IQM client:

1. The recommended way is to use Cortex CLI to manage the authentication tokens and store them into a file. IQM client can then read the token from the file and use it for authentication. The file path can be provided to IQM client in environment variable IQM_TOKENS_FILE. Alternatively, the tokens file path can be provided as argument tokens_file to IQMClient constructor.

2. It is also possible to use plaintext token obtained from a server dashboard. These tokens may have longer lifespan than access tokens generated by Cortex CLI, and thus IQM client won’t attempt to refresh them. The generated token can be provided to IQM client in environment variable IQM_TOKEN. Alternatively, the token can be provided as argument token to IQMClient constructor.

3. The third way is to provide server URL, username and password for obtaining the token from an authentication server. IQM client will maintain a login session with the authentication server and read and refresh the token as needed. The server URL, username and password can be provided to IQM client in environment variables IQM_AUTH_SERVER, IQM_AUTH_USERNAME and IQM_AUTH_PASSWORD. Alternatively, the values can be provided as arguments auth_server_url, username and password to IQMClient constructor. Note, that all the values must be provided as either environment variables or as constructor arguments, not mixed.

Circuit transpilation#

IQM does not provide an open source circuit transpilation library, so this will have to be supplied by the quantum computing framework or a third party library. To obtain the necessary information for circuit transpilation, IQMClient.get_dynamic_quantum_architecture() returns the names of the QPU components (qubits and computational resonators), and the native operations available in the given calibration set. This information should enable circuit transpilation for the IQM Crystal quantum architectures.

The notable exception is the transpilation for the IQM Star quantum architectures, which have computational resonators in addition to qubits. Some specialized transpilation logic involving the MOVE gates specific to these architectures is provided, in the form of the fuctions transpile_insert_moves() and transpile_remove_moves(). See iqm.iqm_client.transpile for the details.

A typical Star architecture use case would look something like this:

from iqm.iqm_client import Circuit, IQMClient, simplify_architecture, transpile_insert_moves, transpile_remove_moves

client = IQMClient(URL_TO_STAR_SERVER)
dqa = client.get_dynamic_quantum_architecture()
simplified_dqa = simplify_architecture(dqa)

# circuit valid for simplified_dqa
circuit = Circuit(name="quantum_circuit", instructions=[...])

# intended use
circuit_with_moves = transpile_insert_moves(circuit, dqa)
client.submit_circuits([circuit_with_moves])

# back to simplified dqa
circuit_without_moves = transpile_remove_moves(circuit_with_moves)
assert circuit == circuit_without_moves

Note on qubit mapping#

We encourage to transpile circuits to use the physical IQM qubit names before submitting them to IQM quantum computers. In case the quantum computing framework does not allow for this, providing a qubit mapping can do the translation from the framework qubit names to IQM qubit names. Note, that qubit mapping is not supposed to be associated with individual circuits, but rather with the entire job request to IQM server. Typically, you would have some local representation of the QPU and transpile the circuits against that representation, then use qubit mapping along with the generated circuits to map from the local representation to the IQM representation of qubit names. We discourage exposing this feature to end users of the quantum computing framework.

Note on circuit duration check#

Before performing circuit execution, IQM server checks how long it would take to run each circuit. If any circuit in a job would take too long to execute compared to the T2 time of the qubits, the server will disqualify the job, not execute any circuits, and return a detailed error message. In some special cases, it makes sense to adjust or disable this check using the max_circuit_duration_over_t2 attribute of CircuitCompilationOptions, and then passing the options to IQMClient.submit_circuits().

Note on environment variables#

Set IQM_CLIENT_REQUESTS_TIMEOUT environment variable to override the network requests default timeout value. The default value is 60 seconds and might not be sufficient when fetching run results of larger circuits via slow network connections.

On Linux:

$ export IQM_CLIENT_REQUESTS_TIMEOUT=120

On Windows:

set IQM_CLIENT_REQUESTS_TIMEOUT=120

Once set, this environment variable will control network request timeouts for IQMClient methods abort_job, get_quantum_architecture, get_dynamic_quantum_architecture, get_run, and get_run_status.

Set IQM_CLIENT_SECONDS_BETWEEN_CALLS to control the polling frequency when waiting for compilation and run results with the IQMClient.wait_for_compilation() and IQMClient.wait_for_results() methods. The default value is set to 1 second.

Set IQM_CLIENT_DEBUG=1 to print the run request when it is submitted for execution in IQMClient.submit_circuits() or IQMClient.submit_run_request(). To inspect the run request without sending it for execution, use IQMClient.create_run_request().

Integration testing#

IQM provides a demo environment to test the integration against a mock quantum computer. If you’d like to request access to that environment, please contact IQM.