Quantum-as-a-Service for VS Code

Run OpenQASM 3 and Qiskit circuits on the VLQ quantum computer from VS Code, through LEXIS and HEAppE, using the qaas Python package (QHEAppE client).

Features and roadmap

Status: ✅ available and tested (live items verified on VLQ, 2026-11-11) · 🔶 available, not yet verified against live VLQ · ⚠️ available, blocked by a server-side issue · 🗓️ planned

Python environment

Login and backends

OpenQASM 3

Python scripts and notebooks

Job manager

Results and analysis

Billing estimate

Calibrations

Pulse-level operator catalog

Platform support

Developed and tested on macOS (Apple silicon, VS Code 1.145). Compatibility with Windows and Linux still has to be checked. Areas that differ per platform and need testing there:

Operator files

# .qaas/operators/hann_drag.yaml
schema: qaas-operator/v1
name: hann_drag                 # implementation name for the IQM compiler
gate: prx
description: Hann pulse with DRAG
parameters:                     # shared by I and Q; unit s = seconds, Hz, or dimensionless
  width: { default: 0.2 }
waveform:
  i: { type: expression, expression: "cos(pi * t) ** 2" }   # t in [-1/2, 1/2] of the pulse
  q: { type: derivative }                                    # or zero / builtin / expression / samples
calibrations:
  - calibrationSetId: 7f3c…      # calibration set the values were tuned on
    backend: VLQ
    status: calibrated          # or draft (seeded / migrated, not verified)
    verifiedLoci: [QB1]
    reference: { implementation: drag_crf, loci: { QB1: { duration: 4.0e-8, amplitude_i: 0.31 } } }
    loci:
      QB1: { duration: 4.0e-8, amplitude_i: 0.42, amplitude_q: 0.02 }

• Built-in shapes: { type: builtin, name: Gaussian } and other waveforms from iqm.models.playlist.waveforms. Their fields become parameters (time-like ones in seconds).
• Expressions: arithmetic, **, %, pi, e, comparisons inside where, and sin cos tan arcsin arccos arctan sinh cosh tanh exp log sqrt abs sign minimum maximum clip where heaviside.
• Samples: values in [-1, 1], linearly interpolated over the pulse.
• Values per qubit: duration, amplitude_i, amplitude_q, and any parameter to override for that qubit.
• OpenQASM 3: add // @qaas operator prx=hann_drag to run the file at pulse level with the operator.
• Calibration results from the Rabi notebook are written to .qaas/calibrations/*.json.

Billing estimate

Pulse-level operator catalog

Billing estimate

billed [s] = VLQ jobs × max(shots × (350 µs + circuit time), 0.9 s)      circuit time ≤ 50 µs

qaas sends every circuit of a batch as its own HEAppE task, so the extension counts each circuit as one VLQ job, each with the 0.9 s minimum. Unless the circuit time is known, estimates are shown as a range: 350 µs per shot (low) to 400 µs per shot (worst case, use for budgeting). Submission latency of 3–15 s is not billed.

Settings

Scripts started with Run Python File on VLQ get LEXIS_PROJECT, LEXIS_RESOURCE, QAAS_BACKEND, LEXIS_TOKEN and, for a non-production instance, PY4LEXIS_AAI_URL, PY4LEXIS_API_URL and PY4LEXIS_REALM as environment variables. LEXIS_TOKEN is always a short-lived access token issued by the bridge (also after a browser login), never the stored refresh token, because everything started in that terminal can read it. Scripts that still need LEXIS after it expires (usually minutes; the expiry is shown when the script starts) must be run again.

Testing against the LEXIS test instance

Run QaaS: Open Dev Connection File. It creates .qaas/dev.env (and adds it to .qaas/.gitignore) with these keys:

PY4LEXIS_AAI_URL=<login (Keycloak) URL of the instance>
PY4LEXIS_API_URL=<LEXIS Platform API URL of the instance>
PY4LEXIS_REALM=<Keycloak realm of the instance>
QAAS_LEXIS_PROJECT=<test project>
QAAS_LEXIS_RESOURCE=<test resource>
# QAAS_BACKEND_NAME=VLQ
QAAS_LEXIS_TOKEN=<refresh or offline token>

• Values in the file override the qaas.* settings and the stored token; changes apply to the next request, no reload needed. Delete or rename the file to go back to production.
• A refresh/offline token is exchanged for access tokens by py4lexis and renewed as they expire. An access token works too but expires within minutes. Without a token, the browser login opens on the test instance.
• The status bar shows e.g. VLQ · LEXIS test on a warning background while the file points at a non-production instance. Jobs record their instance, so test and production jobs can share the Jobs view and are always refreshed against the right one.
• QaaS: Test LEXIS Connection logs in, prints the user, token kind and expiry, and lists the backends in the QaaS output channel.
• Instead of the file, the URLs can be set with qaas.lexisAaiUrl, qaas.lexisApiUrl and qaas.lexisRealm (e.g. in workspace settings), and the token with Set LEXIS Token.
• A token is only ever sent to the instance it belongs to. Order: the dev file's token (when the file selects that instance), the token stored for that instance with Set LEXIS Token or Sign in, then the QAAS_LEXIS_TOKEN environment variable (production only). A workspace or dev file that points at another server therefore gets no stored token; sign in again there.
• The extension is disabled in untrusted (Restricted Mode) workspaces. In trusted ones, values a cloned repository could plant are used only after you allow them once per folder: a non-production LEXIS login set by workspace settings or the dev file (the browser login would show that server's page), qaas.pythonPath / qaas.condaPath from workspace settings, an interpreter inside the workspace picked by the Python extension, and a workspace qaas.resultsDirectory outside the workspace. Instances and paths from your user settings need no approval.

How it works

The extension does not reimplement the client. It starts python/qaas_bridge.py once with your interpreter and talks to it over stdin/stdout (one JSON request and response per line). The process keeps the LEXIS login and HEAppE clients alive, and calls qheappe_client (QProvider, QBackend, QJob). Library output goes to the QaaS output channel. py4lexis writes its log (no tokens) to lexis.log in the extension's log folder (Developer: Open Extension Logs Folder), readable by your user only.

Development

npm install
pip install -r requirements-dev.txt   # ruff
npm run compile        # or: npm run watch, then F5 for an Extension Development Host
npm run test:unit      # estimator, scanner, statistics, catalog model (node --test)
npm run test:py        # Python bridge and operator code generator (needs qaas[iqm_qiskit])
npm test               # integration tests in a downloaded VS Code
npm run lint           # Biome (TypeScript/JSON) + Ruff (Python)
npm run format         # format everything
npm run package        # build a .vsix

Formatting and linting: Biome for TypeScript, JavaScript and JSON; Ruff for Python. The workspace recommends both VS Code extensions and formats on save.

Authors

Developed at IT4Innovations National Supercomputing Center, VSB - Technical University of Ostrava.

• Ing. Jan Swiatkowski
• Ing. Jan Martinovič, Ph.D.

License

Apache-2.0