QCOS Studio

A quantum programming language and its editor, inside VS Code.

QCOS Studio is the VS Code extension for the QCOS language. You write a quantum program as readable text, with named qubits and real control flow, and the editor helps you as you type. Through the QCOS API it checks the program, compiles it for a target and runs it on a simulator.

program prepare_one
qubits q
bits m

h q
measure q -> m

// Try again until the qubit reads 1, at most 16 times.
while !m budget 16 {
  reset q
  h q
  measure q -> m
}

Why install it

Read your circuit as a program. Qubits have names, loops and branches are part of the language, and routines let you reuse a piece of a circuit instead of copying it.
Learn the language as you write. Completion offers every gate and keyword. Hover shows how a keyword is used, and how many qubits and angles a gate takes. No account or API key is needed for this.
Limits are written in the source. A real-time loop must state its budget, so a program can't loop without bound.
See what the compiler did. Compile shows the circuit drawn for the target you chose, with its metrics, next to your source.
Clear refusals. When a target can't take your program, the extension says which target and why. It never shows a fake result or an invented price.
Evidence you can check. A run leaves a receipt, and you can verify it from the editor, including its signature with the local QuantumLock verifier.

What works today

This is a preview. The QCOS language service is not enabled on the production API yet.

Feature	Today	Needs
Highlighting, outline, completion, hover	Works	Nothing: no account, no key, no network
Problems, gate counts, control-flow view	Not yet in production	QCOS API with the language service enabled
Compile, Estimate Resources	Not yet in production	The same, and an API key with `qcos:execute`
Run on a simulator	Not yet in production	The same, and an available simulator
Run on a real quantum computer	Off	Real QPU execution is disabled

Until the service is enabled, those commands answer that the API does not offer them yet. If your organization has been given another QCOS API address, set it in qcos.apiUrl.

Who it is for

Researchers and developers who want quantum programs that a colleague can read and review.
Teams writing programs with measurement-driven control, such as repeat-until-success or error-correction routines.
Anyone learning the language: the editor features work from the first minute, with nothing to set up.

Getting started

Install the extension and create a file ending in .qcos. The imperative L2 form uses .qcos2.
Type a program. Use completion for gates and keywords, hover for their meaning, and the Outline view to move around.
When you have QCOS API access, run QCOS: Set API Key. The key is kept in VS Code's secret storage.
Save the file to check it. Problems appear in the editor.
Use Compile, Estimate Resources and Run above the program line, and choose where they go with Target.

Commands

Command	What it does
QCOS: Compile	Compiles for the chosen target and draws the result. Nothing runs on hardware
QCOS: Estimate Resources	Shows logical resources and the compiled metrics
QCOS: Run Program	Runs the program with the shots from `qcos.shots`, and shows the distribution and the receipt
QCOS: Select Target / Inspect Target	Chooses a target and shows what it offers
QCOS: Show Control Flow	Draws the branches and loops of the program
QCOS: Verify QuantumLock Receipt	Checks the evidence of a run
QCOS: Set API Key / Clear API Key	Stores or removes your key

Your code and your key

Your source leaves your machine only through the QCOS API. Each save sends it for checking, unless you turn off qcos.checkOnSave. Compile and Run happen only when you ask.
A repository can't redirect your key. qcos.apiUrl is a user setting that a workspace can't change, and it must be https, except on localhost.
A repository can't choose what runs on your machine. The verifier command is a user setting too.
Untrusted workspaces are not supported, because the extension sends source to the API with your key.

What it refuses, and why

Programs with real-time control (while, or if/match on a measurement) are checked, shown and compiled for a target that offers what they need; a target that does not is refused by name. No run route takes them yet, so Run refuses.
Cost. QCOS does not price. Quotes come from the Softquantus Research Platform.
Signature verification. QCOS confirms a receipt's hashes, at most "sealed, unsigned". Verified (ML-DSA-65) comes only from the local QuantumLock verifier (pip install "quantumlock[pqc]") against the trust root in qcos.quantumlock.trustRootPin. Without either, a claimed signature is shown as claimed, not confirmed.
Classical synthesis and the QUARTZ_6003 inspector have no backend yet.

Settings

qcos.apiUrl: API base URL; https only, except localhost. User setting only.
qcos.checkOnSave: check on save (default on). Each save sends the source to the API.
qcos.shots: shots for Run.
qcos.quantumlock.command: the local verifier command.
qcos.quantumlock.trustRootPin: the trust root you accept, as sha256:<hex>.

QCOS Studio — Quantum Development Environment

SoftQuantus