openqasm/README.md

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# OpenQASM
OpenQASM is an imperative programming language for describing quantum circuits. It is capable of
describing universal quantum computing using the circuit model, measurement-based model,
and near-term quantum computing experiments.
This repo contains the OpenQASM specification, examples, and tools for the OpenQASM intermediate representation.
OpenQASM is a [Qiskit project](https://qiskit.org).
## :bangbang: Call for Applicants for TSC Secreatary! :bangbang:
We are searching for candidates for the role of [TSC Secretary](governance.md#tsc-secretary).
The TSC will select a new Secretary during a TSC meeting in April, 2025.
Candidates should familiarize themselves with the [responsibilties of the role](governance.md#tsc-secretary).
If you are interested in presenting yourself as a candidate, please contact Jack Woehr,
the current Secretary, at [jack.woehr@procern.com](mailto:jack.woehr@procern.com) before April, 2025.
## Current version: **3.1**
* Live language specification [**version 3.1**](https://openqasm.github.io/)
* The branch of this repository for the previous version: [OpenQASM 2.0](https://github.com/openqasm/openqasm/tree/OpenQASM2.x)
## About this project
In this repository, you'll find all the documentation related to OpenQASM, some useful OpenQASM examples, and [plugins for some text editors](#plugins).
### Language specs
The live [language documentation](https://openqasm.github.io/) specification.
### Examples
An example of OpenQASM 3.0 source code is given below. Several more examples may be found in the [examples folder](examples).
```text
/*
* Repeat-until-success circuit for Rz(theta),
* cos(theta-pi)=3/5, from Nielsen and Chuang, Chapter 4.
*/
OPENQASM 3;
include "stdgates.inc";
/*
* Applies identity if out is 01, 10, or 11 and a Z-rotation by
* theta + pi where cos(theta)=3/5 if out is 00.
* The 00 outcome occurs with probability 5/8.
*/
def segment qubit[2] anc, qubit psi -> bit[2] {
bit[2] b;
reset anc;
h anc;
ccx anc[0], anc[1], psi;
s psi;
ccx anc[0], anc[1], psi;
z psi;
h anc;
measure anc -> b;
return b;
}
qubit input;
qubit[2] ancilla;
bit[2] flags = "11";
bit output;
reset input;
h input;
// braces are optional in this case
while(int(flags) != 0) {
flags = segment ancilla, input;
}
rz(pi - arccos(3 / 5)) input;
h input;
output = measure input; // should get zero
```
## Citation format
For research papers, we encourage authors to reference.
- [Version 3.0] Andrew W. Cross, Ali Javadi-Abhari, Thomas Alexander, Niel de Beaudrap, Lev S. Bishop, Steven Heidel, Colm A. Ryan, John Smolin, Jay M. Gambetta, Blake R. Johnson "OpenQASM 3: A broader and deeper quantum assembly language" [[arxiv:2104.14722]](https://arxiv.org/abs/2104.14722).
- [Previous Version: 2.0] Andrew W. Cross, Lev S. Bishop, John A. Smolin, Jay M. Gambetta "Open Quantum Assembly Language" [[arXiv:1707.03429]](https://arxiv.org/abs/1707.03429).
## Governance
The OpenQASM project has a process for accepting changes to the language and making decisions codified in its [governance model](governance.md).
## License
This project is licensed under the Apache License 2.0 - see the [LICENSE](./LICENSE) file for details.
## Contributing
If you'd like to help please take a look to our [contribution guidelines](CONTRIBUTING.md). This project adheres to a [Code of Conduct](./CODE_OF_CONDUCT.md). By participating, you are expected to uphold this code.
## Release Notes
See the section on Release Notes [contribution guidelines](CONTRIBUTING.md#release-notes).