> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ionq.com/llms.txt
> Use this file to discover all available pages before exploring further.

# API v0.4 Reference

> The IonQ Quantum Cloud API lets you submit quantum circuits, manage jobs, and access quantum computing resources programmatically. 

## Quick Start

* **New to IonQ?** Most users start with an [SDK like Qiskit](/sdks) rather than calling the API directly.
* **Migrating from v0.3?** Check our [migration guide](/api-reference/v0.4/migration-from-v0.3) for breaking changes and new features.
* **Need help?** Join our [community Slack](https://join.slack.com/t/ionqcommunity/shared_invite/zt-2ohj4fkvb-ErVKebhkwaP7S~lt2Gq0_w) or contact [support@ionq.com](mailto:support@ionq.com).

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## What's New in v0.4

* **Enhanced cost tracking** - New dedicated endpoint for job billing details
* **Improved results structure** - Cleaner separation of job metadata and probability data
* **Better backend organization** - Characterizations now nested under backends
* **Streamlined pagination** - Consistent filtering across list endpoints

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## System Status

Check real-time API and hardware status at [status.ionq.co](https://status.ionq.co) or view backend availability in the [Quantum Cloud console](https://cloud.ionq.com/backends).