Runtime

The runtime is the vendor’s service that accepts a circuit, fits it to a real chip, and runs the shots. FQkit keeps one interface in front of two runtimes: Qiskit Runtime for IBM, and Amazon Braket for IonQ, Rigetti, IQM, and AQT.

run() is not part of this. It never logs in, never queues, and never leaves your computer. Use it to check a circuit before you spend a queue slot or a billed task.

What happens on IBM

submit(qc, "ibm") does five things:

Export the circuit as OpenQASM 2.0, including a measurement of every qubit.
Load that text into Qiskit.
Ask IBM for a real device. With no backend, that is the least busy device that is operational and is not a simulator.
Transpile the circuit for that device. The transpiler rewrites gates into the chip’s own gate set and inserts swaps where two qubits are not neighbors.
Send the rewritten circuit to the Qiskit Runtime Sampler. The Sampler returns a job id. The job waits in the queue, then the chip measures it shots times.

job.status() calls the Runtime again and returns one word. It does not wait.

What happens on Braket

submit(qc, "ionq"), "rigetti", "iqm", or "aqt" does the matching work through Amazon Braket:

Write the circuit as OpenQASM 3.0. Braket does not take FQkit’s OpenQASM 2.0 string.
Open the device named by that machine. The built-in targets are IonQ Forte-1, Rigetti Ankaa-3, IQM Garnet, and AQT IBEX-Q1.
Call device.run. Braket compiles the program for that device and returns a task. The task ARN is job.job_id.
job.status() reads the task state. job.counts() waits until the task completes, then reads measurement_counts.

Status words

Every vendor’s private status is mapped onto the same five words:

Word	Meaning
`QUEUED`	Accepted, and waiting. IBM’s initializing state is included here.
`RUNNING`	The device is executing the shots.
`COMPLETED`	Results are ready. IBM calls this done.
`CANCELLED`	The job was cancelled before it finished.
`FAILED`	The vendor reported an error.

An unknown vendor word is returned unchanged, in uppercase, so a new status is still visible.

Checks before a job is sent

FQkit stops early when the circuit or the call cannot be sent:

An unbound Parameter raises ValueError. Bind it first.
shots below 1 raises ValueError.
An unknown machine name raises UnknownMachine. The message lists ibm, ionq, rigetti, iqm, and aqt.
A missing SDK raises ProviderNotInstalled with the pip install line.

The vendor can still reject the job after that. A circuit wider than the chip, or a compiled circuit past a device’s gate limit, fails in the runtime. Read job.status() if it becomes FAILED.

What is not a runtime target

Quantinuum uses its own account system and is not one of these extras. QuEra Aquila is an analog device, so an FQkit gate circuit is not sent there. backends("braket", live=True) also skips it when listing online QPUs.

Next: Job submission.