Architecture¶

Layer design¶

QaaS is structured as three layers:

graph TD
    User["User code\n(Qiskit circuits)"]
    P["Provider layer\nprovider.py"]
    C["Client layer\nclient.py"]
    B["Backend layer\nbackend_iqm.py"]
    HEAppE["HEAppE\n(job scheduler)"]
    IQM["IQM hardware"]

    User --> P
    P --> C
    P --> B
    C --> HEAppE
    B --> IQM
    HEAppE --> IQM

Provider layer (provider.py)¶

Authenticates against the LEXIS platform using the supplied token and project name, then resolves the requested resource to a concrete backend implementation. This is the only layer the user interacts with directly.

Client layer (client.py)¶

Handles HEAppE job lifecycle: submission, polling, result retrieval, and error propagation back to the caller. Internally manages encrypted credentials and accounting information.

Backend layer (backend_iqm.py)¶

Creates IQM-specific QBackend instances. Fetches real-time hardware calibration data, drives circuit transpilation through the IQM gate set, and wraps raw IQM results into the QJob/result abstraction.

HEAppE execution flow¶

Jobs travel through the following steps once backend.run() is called:

1. Submission — circuit and parameters are packaged into a HEAppE command template and submitted.
2. Initialisation (run_init.sh) — the remote environment is set up; hardware availability and system information are verified.
3. Execution (run_execution.sh) — the quantum circuit is dispatched to IQM hardware and run for the requested number of shots.
4. Result retrieval — measurement counts are collected by HEAppE and streamed back to the QaaS client, which surfaces them via job.result().get_counts().

Key design decisions¶

• Hardware-specific transpilation is performed client-side before submission so that the backend always receives a valid native-gate circuit.
• Real-time calibration is fetched at backend creation time, ensuring transpilation targets the current hardware state.
• IQM pulse-level optimisation (iqm-pulla) is available as an optional post-transpilation step for advanced users.

Roadmap¶