Before you spend credits

Every simulator on Qollab is free and only the quantum computers spend credits, so the run that costs something is worth four checks first. IonQ publishes a submission checklist for their own users; this is the same sequence for a platform where the API key and the account belong to Qollab.

1. Get the circuit right on the built-in simulator

The built-in simulator is free, runs in your browser, and never queues. It catches the things that have nothing to do with quantum mechanics: a syntax error, a qubit index out of range, a measurement you forgot to add.

It also confirms the circuit compiles at all. IonQ's own first checklist item is to test on their ideal simulator for exactly this reason, and the built-in simulator fills that role here.

2. Size your shots on a noise-model simulator

Getting a correct circuit is not the same as knowing how many shots you need. That answer depends on noise, and the built-in simulator has none.

Run it again on an IonQ remote simulator, which carries the noise model of the machine you are aiming at. The distribution you get back is a realistic preview, and it tells you whether 100 shots resolves your answer or whether you need 1,000.

Two things to know before you do. It is slower than the built-in simulator, because noise-model simulation is shot-aware: IonQ runs one simulation for every shot you request, so a large shot count means many simulations. And it is still a model: IonQ is explicit that you should not expect QPU results to match noisy simulation results quantitatively. Those models are simplified approximations of what hardware would do, not a replacement for running on it. See Compute backends.

3. Check the machine is online

Hardware is not always available. A backend that is down shows as offline in the Select QPU dialog, and IonQ publishes maintenance and availability at status.ionq.co.

What the dialog does not tell you is how long the line is. It says a machine is available, not how many jobs are ahead of you, so the queue is invisible at the moment you are choosing.

It stops being invisible once you submit. While a hardware job waits, the run console prints IonQ's own predicted waiting time for that circuit, so the estimate arrives after the decision rather than before it. Plan for a hardware run to resolve on its own schedule, and see Running your code for the job states you will pass through.

4. Confirm the price

Qollab asks before it spends. The runner shows the cost in credits next to your balance and waits for you to approve; decline and nothing is charged.

Two details matter. The figure quoted before the run is usually an estimate, and once the job finishes the runner replaces it with the actual credits withdrawn, which can differ. And the allowance that decides whether you are asked at all lives in the runner, not in your profile settings, starting at a tenth of your balance and editable before you run.

If the estimate is higher than you expected, the usual causes are shot count and a circuit that compiled larger than you wrote it. See How credits work and How your circuit is compiled.

Related

• How credits work
• Compute backends
• Running your code
• How your circuit is compiled

The checklist this page adapts is IonQ's QPU submission checklist, and the simulation caveats are from their noise model guide. Both are the source of truth. Crawled 2026-09-09.