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Quantum Information Science Kit (QISKit)

Swift software development kit (SDK) for working with OpenQASM and the IBM Q experience (QX).


The basic concept of our quantum program is an array of quantum circuits. The program workflow consists of three stages: Build, Compile, and Run. Build allows you to make different quantum circuits that represent the problem you are solving; Compile allows you to rewrite them to run on different backends (simulators/real chips of different quantum volumes, sizes, fidelity, etc); and Run launches the jobs. After the jobs have been run, the data is collected. There are methods for putting this data together, depending on the program. This either gives you the answer you wanted or allows you to make a better program for the next instance.


Swift example programs can be found in the examples directory, and test scripts are located in test. The qiskit directory is the main module of the SDK.


Programming interface

The qiskit directory is the main Swift Framework and contains the programming interface objects QuantumProgram, QuantumRegister, ClassicalRegister, and QuantumCircuit.

At the highest level, users construct a QuantumProgram to create, modify, compile, and execute a collection of quantum circuits. Each QuantumCircuit has a set of data registers, each of type QuantumRegister or ClassicalRegister. Methods of these objects are used to apply instructions that define the circuit. The QuantumCircuit can then generate OpenQASM code that can flow through other components in the qiskit directory.

The extensions directory extends quantum circuits as needed to support other gate sets and algorithms. Currently there is a standard extension defining some typical quantum gates.

Internal modules

The directory also contains internal modules that are still under development:

  • a qasm module for parsing OpenQASM circuits
  • an unroll module to interpret and "unroll" OpenQASM to a target

gate basis (expanding gate subroutines and loops as needed) - a circuit module for working with circuits as graphs - a mapper module for mapping all-to-all circuits to run on devices with fixed couplings

Quantum circuits flow through the components as follows. The programming interface is used to generate OpenQASM circuits. OpenQASM source, as a file or string, is passed into a Qasm object, whose parse method produces an abstract syntax tree (AST). The AST is passed to an Unroller that is attached to an UnrollerBackend. There is a PrinterBackend for outputting text, a JsonBackend for outputting JSON data, a CircuitBackend for constructing QuantumCircuit objects and a DAGBackend for constructing DAGCircuit objects. The DAGCircuit object represents an "unrolled" OpenQASM circuit as a directed acyclic graph (DAG). The DAGCircuit provides methods for representing, transforming, and computing properties of a circuit and outputting the results again as OpenQASM. The whole flow is used by the mapper module to rewrite a circuit to execute on a device with fixed couplings given by a CouplingGraph.

The four circuit representations and how they are currently transformed into each other are summarized in this figure:


Installation and setup

1. Get the tools

You'll need:

2. Get the code

Clone the QISKit SDK repository and navigate to its folder on your local machine:

  • If you have Git installed, run the following commands:
git clone
cd qiskit-sdk-swift
  • If you don't have Git installed, click the "Clone or download" button at the URL shown in the git clone command, unzip the file if needed, then navigate to that folder in a terminal window.

3. Alternatively install using Carthage

4. Configure your API token

  • Create an IBM Quantum Experience account if you haven't already done so
  • Get an API token from the Quantum Experience website under “My Account” > “Personal Access Token”
  • When developing your own project, you will pass your API token to the QuantumProgram instance set_api method. Please see the examples under Sources/examples/ or the playground tutorial.

5. Build and run the Swift Playground Tutorial

  • Run carthage update to pull the latest Swift qiskit:
  • Open the QisSwiftPlayground.xcodeproj
  • Compile the qiskit framework
  • Add your API token to the file "QisSwiftDeveloperTutorial.playground"
  • Swift Playgrounds run automatically

6. Using Swift Package Manager (OSX and Ubuntu)

  • For Ubuntu download and install the latest Swift runtime from
  • From the top folder, run "swift build" or "swift test" to run the Unit tests
  • Once "swift build" is run, you can try the command line examples from .build/debug/qiskitexamples program. If you run without options, it will show correct usage.

Authors (alphabetical)

Jim Challenger, Andrew Cross, Ismael Faro, Jay Gambetta, Juan Gomez, Joe Ligman, Manoel Marques, Paco Martin, Antonio Mezzacapo, Jesus Perez, and John Smolin, Erick Winston, Chris Wood.

In future releases, anyone who contributes code to this project can include their name here.

Other QISKit projects


QISKit is released under the Apache license, version 2.0.

Do you want to help?

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

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