Q# (pronounced as ''Q sharp'') is a domain-specific programming language used for expressing quantum algorithms. It was initially released to the public by Microsoft as part of the Quantum Development Kit.

History

Historically,

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had two teams interested in quantum computing, the QuArC team based in Redmond, directed by

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, that explored the construction of quantum circuitry, and Station Q initially located in Santa Barbara and directed by Michael Freedman, that explored topological quantum computing. During a Microsoft Ignite Keynote on September 26, 2017, Microsoft announced that they were going to release a new programming language geared specifically towards quantum computers. On December 11, 2017, Microsoft released Q# as a part of the Quantum Development Kit. At

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, Microsoft announced that it is open-sourcing the Quantum Development Kit, including its Q# compilers and simulators. Bettina Heim currently leads the Q# language development effort.

Usage

Q# is available as a separately downloaded extension for Visual Studio, but it can also be run as an independent tool from the Command line or Visual Studio Code. The Quantum Development Kit ships with a quantum simulator which is capable of running Q#. In order to invoke the quantum simulator, another .NET programming language, usually C#, is used, which provides the (classical) input data for the simulator and reads the (classical) output data from the simulator.

Features

A primary feature of Q# is the ability to create and use qubits for algorithms. As a consequence, some of the most prominent features of Q# are the ability to entangle and introduce superpositioning to qubits via Controlled NOT gates and Hadamard gates, respectively, as well as Toffoli Gates, Pauli X, Y, Z Gate, and many more which are used for a variety of operations; see the list at the article on quantum logic gates. The hardware stack that will eventually come together with Q# is expected to implement Qubits as topological qubits. The quantum simulator that is shipped with the Quantum Development Kit today is capable of processing up to 32 qubits on a user machine and up to 40 qubits on

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Documentation and resources

Currently, the resources available for Q# are scarce, but the official documentation is published
Microsoft Developer Network: Q#Microsoft Quantum Github repository
is also a large collection of sample programs implementing a variety of Quantum algorithms and their tests. Microsoft has also hosted a Quantum Coding contest on Codeforces here
Microsoft Q# Coding Contest - Codeforces
and also provided related material to help answer the questions in the blog posts, plus the detailed solutions in the tutorials. Microsoft hosts a set of learning exercises to help learn Q# on GitHub
microsoft/QuantumKatas
with links to resources, and answers to the problems.

Syntax

Q# is syntactically related to both C# and F# yet also has some significant differences.

Similarities with C#

* Uses for code isolation * All statements end with a * Curly braces are used for statements of scope * Single line comments are done using * Variable data types such as and are similar, although capitalised (and Int is 64-bit) * Qubits are allocated and disposed inside a block. * Lambda functions using the => operator. * Results are returned using the keyword.

Similarities with F#

* Variables are declared using either or * First-order functions * Modules, which are imported using the keyword * The datatype is declared after the variable name * The range operator * loops * Every operation/function has a return value, rather than . Instead of , an empty Tuple is returned. * Definition of record datatypes (using the keyword, instead of ).

Differences

* Functions are declared using the keyword * Operations on the quantum computer are declared using the keyword * Lack of multiline comments * Asserts instead of throwing exceptions * Documentation is written in Markdown instead of XML-based documentation tags

Example

The following source code is a multiplexer from the official Microsoft Q# library repository. // Copyright (c) Microsoft Corporation. // Licensed under the MIT License. namespace Microsoft.Quantum.Canon

References

External links

* * {{Microsoft development tools Free and open-source software Microsoft free software Microsoft programming languages Quantum programming Programming languages created in 2017 Software using the MIT license