Capturing runs

Capture is how quantum jobs get into the ledger. It happens client-side in the open-source quantumledger SDK, works offline, and needs no account.

Three ways to capture

Pick whichever fits your code:

Decorator — wrap the function that submits the job. Cleanest for scripts.
Context manager — wrap just the submission block when you can't decorate.
CLI — run an existing callable under capture without editing its source.

When the wrapped code returns, the SDK intercepts the circuit, backend, calibration and result and writes an immutable run to your local ledger.

If a connector can't extract a field (e.g. live calibration is unavailable), it records a gap flag rather than fabricating data — honesty about missing data is part of the provenance guarantee.

import quantumledger as ql

@ql.capture(project="my-experiment")
def run():
    return backend.run(circuit, shots=4096)

import quantumledger as ql

with ql.capture(project="my-experiment"):
    result = backend.run(circuit, shots=4096)

ql capture-target mymod:run --project my-experiment

The local ledger

Captured runs land in a local SQLite store — the same schema the hosted server uses, so a run's run_hash is identical whether it lives locally or in the cloud.

ql list
ql show <run_id>

Vendor connectors

Extraction is pluggable: a connector knows how to pull the circuit, backend, calibration and result out of one vendor's native objects. Connectors are discovered as entry-point plugins, so installing a connector package makes it available automatically.

Connector	Vendor / SDK	Install extra
`simulator`	Qiskit Aer (local)	`quantumledger[aer]`
`qiskit_runtime`	IBM Quantum	`quantumledger[qiskit_runtime]`
`braket`	Amazon Braket	`quantumledger[braket]`
`azure_quantum`	Azure Quantum	`quantumledger[azure]`
`ionq`	IonQ	(bundled)

ql connectors          # list what's discovered in your environment

Writing a custom connector

Subclass quantumledger.connectors.base.Connector, implement extraction into a CaptureBundle, and register it under the quantumledger.connectors entry-point group. It's then discoverable by ql connectors and usable by @ql.capture with no further wiring.

Next: Reproduce & drift.