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OpenQASM is an imperative programming language for describing quantum circuits. It is capable to describe universal quantum computing using the circuit model, measurement-based model, and near-term quantum computing experiments.

Specs, examples and tools for the OpenQASM intermediate representation.

Current version: 3.0

Live doc: version 3.0

For previous version see: 2.0

About this project

On this repository, you'll find all the documentation related to OpenQASM and some useful OpenQASM examples.

Language specs

The live language documentation specification.


The examples can be found under the examples folder.

They are OpenQASM files, i.e.:

 * Repeat-until-success circuit for Rz(theta),
 * cos(theta-pi)=3/5, from Nielsen and Chuang, Chapter 4.
include "";

 * 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].
  • [Previous Version: 2.0] Andrew W. Cross, Lev S. Bishop, John A. Smolin, Jay M. Gambetta "Open Quantum Assembly Language" [arXiv:1707.03429].


This project is licensed under the Apache License 2.0 - see the [LICENSE] file for details.


If you'd like to help please take a look to our contribution guidelines.