{{Short description|Programming language for quantum algorithms}} {{Correct title|title=Q# (programming language)|reason=hash}} {{third-party|date=September 2018}} {{Infobox programming language | title = Q# | released = {{Start date|2017|12|11}}<ref name="AT Q#">{{Cite web|url=https://arstechnica.com/gadgets/2017/12/microsofts-q-quantum-programming-language-out-now-in-preview/|title=Microsoft's Q# quantum programming language out now in preview |website=Ars Technica |date=12 Dec 2017 |access-date=2024-09-04|language=en-US}}</ref> | developer = Microsoft | designer = Microsoft Research (quantum architectures and computation group; QuArC) | influenced by = C#, F#, Python | File extensions = .qs | platform = Common Language Infrastructure | paradigm = Quantum, functional, imperative | typing = Static, strong | license = MIT License<ref>{{cite web |title=Introduction to Q# |url=https://courses.cs.washington.edu/courses/cse490q/20au/hws/qsharp-intro.pdf |publisher=University of Washington}}</ref> | website = {{URL|https://learn.microsoft.com/en-us/azure/quantum/}} | repo = {{URL|[https://github.com/Microsoft/Quantum}} }} {{Portal|Computer programming|Free and open-source software}} '''Q#''' (pronounced ''Q sharp'') is a domain-specific programming language used for expressing quantum algorithms.<ref name=":1">{{Cite web|url=https://docs.microsoft.com/en-us/quantum/quantum-qr-intro?view=qsharp-preview|title=The Q# Programming Language|last=QuantumWriter|website=docs.microsoft.com|language=en-us|access-date=2017-12-11}}</ref> It was initially released to the public by Microsoft as part of the Quantum Development Kit.<ref name=":0">{{Cite news|url=https://cloudblogs.microsoft.com/quantum/2017/12/11/announcing-microsoft-quantum-development-kit/|title=Announcing the Microsoft Quantum Development Kit|access-date=2017-12-11|language=en-US}}</ref>
Q# works in conjunction with classical languages such as C#, Python and F#, and is designed to allow the use of traditional programming concepts in quantum computing, including functions with variables and branches as well as a syntax-highlighted development environment with a quantum debugger.<ref name="AT Q#"></ref><ref name="AT Ignite">{{Cite web|url=https://arstechnica.com/gadgets/2017/09/microsoft-quantum-toolkit/|title=Microsoft makes play for next wave of computing with quantum computing toolkit |date=25 Sep 2017 |website=Ars Technica |access-date=2024-09-04|language=en-US}}</ref><ref>{{Cite web|url=https://www.technologyreview.com/2017/12/22/3662/quantum-computers-barely-exist-heres-why-were-writing-languages-for-them-anyway/|title=Quantum Computers Barely Exist—Here's Why We're Writing Languages for Them Anyway |date=22 Dec 2017 |website=MIT Technology Review |access-date=2024-09-04|language=en-US}}</ref>
==History== Historically, Microsoft Research had two teams interested in quantum computing: the QuArC team based in Redmond, Washington,<ref>{{cite web |title=Solving the quantum many-body problem with artificial neural networks |url=https://cloudblogs.microsoft.com/quantum/2017/02/15/solving-the-quantum-many-body-problem-with-artificial-neural-networks/ |website=Microsoft Azure Quantum |date=15 February 2017}}</ref> directed by Krysta Svore, 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.<ref>Scott Aaronson's blog, 2013, 'Microsoft: From QDOS to QMA in less than 35 years', https://scottaaronson.blog/?p=1471</ref><ref>{{cite web |title=What are the Q# programming language & QDK? - Azure Quantum |url=https://learn.microsoft.com/en-us/azure/quantum/overview-what-is-qsharp-and-qdk |website=learn.microsoft.com |date=12 January 2024 |language=en-us}}</ref>
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.<ref>{{Cite news|url=https://cloudblogs.microsoft.com/quantum/2017/09/26/microsoft-announces-quantum-computing-programming-language/|title=Microsoft announces quantum computing programming language|access-date=2017-12-14|language=en-US}}</ref> On December 11, 2017, Microsoft released Q# as a part of the Quantum Development Kit.<ref name=":0" />
At Build 2019, Microsoft announced that it would be open-sourcing the Quantum Development Kit, including its Q# compilers and simulators.<ref>{{Cite web |url=https://venturebeat.com/2019/05/06/microsoft-open-sourcing-quantum-development-kit/ |title=Microsoft is open-sourcing its Quantum Development Kit |access-date=2020-12-12 |archive-date=2021-01-23 |archive-url=https://web.archive.org/web/20210123111336/https://venturebeat.com/2019/05/06/microsoft-open-sourcing-quantum-development-kit/ |url-status=dead }}</ref>
To support Q#, Microsoft developed Quantum Intermediate Representation (QIR) in 2023 as a common interface between programming languages and target quantum processors. The company also announced a compiler extension that generates QIR from Q#.<ref name="QIR">{{Cite web |title=Microsoft taps LLVM for quantum computing |url=https://www.infoworld.com/article/2260508/microsoft-taps-llvm-for-quantum-computing.html |access-date=2024-09-04 |date=29 Sep 2020 |last1=Krill |first1=Paul |website=InfoWorld |language=en-US}}</ref>
Bettina Heim used to lead the Q# language development effort.<ref>{{cite web | url=https://devblogs.microsoft.com/qsharp/the-women-of-quarc/ | title=The Women of QuArC | date=30 March 2019 }}</ref><ref>{{cite web |title=Intro to Q# - Intro to Quantum Software Development |url=https://stem.mitre.org/quantum/software-tools/intro-qsharp.html |website=stem.mitre.org}}</ref>
==Usage== Q# is available as a separately downloaded extension for Visual Studio,<ref>{{Cite web|url=https://docs.microsoft.com/en-us/quantum/quantum-installconfig?view=qsharp-preview|title=Setting up the Q# development environment|last=QuantumWriter|website=docs.microsoft.com|language=en-us|access-date=2017-12-14}}</ref> but it can also be run as an independent tool from the command line or Visual Studio Code. Q# was introduced on Windows and is available on MacOS and Linux.<ref>{{cite web |last1=Coppock |first1=Mark |title=Microsoft's quantum computing language is now available for MacOS |url=https://www.digitaltrends.com/computing/microsoft-quantum-computing-q-available-macos-linux/ |website=Digital Trends |access-date=2024-09-04 |language=en |date=26 Feb 2018}}</ref>
The Quantum Development Kit includes a quantum simulator capable of running Q# and simulated 30 logical qubits.<ref>{{cite web |last1=Akdogan |first1=Erman |title=Quantum computing is coming for finance & crypto |url=https://medium.datadriveninvestor.com/quantum-computing-is-coming-for-finance-crypto-b56c0255cb09 |website=Medium |language=en |date=23 October 2022}}</ref><ref>{{cite web |last1=Melanson |first1=Mike |title=This Week in Programming: Get Quantum with Q Sharp |url=https://thenewstack.io/week-programming-get-quantum-q-sharp/ |website=The New Stack |access-date=2024-09-04 |language=en |date=16 Dec 2017}}</ref>
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.<ref>{{cite web |title=This Week in Programming: Get Quantum with Q Sharp |url=https://thenewstack.io/week-programming-get-quantum-q-sharp/ |website=The New Stack |date=16 December 2017}}</ref>
==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 quantum logic gates).{{fact|date=January 2025}}
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 Azure.<ref>{{cite web |title=Microsoft previews quantum computing development kit |url=https://www2.cio.com.au/article/631142/microsoft-previews-quantum-computing-development-kit/ |website=CIO |access-date=2022-10-30 |archive-date=2022-10-30 |archive-url=https://web.archive.org/web/20221030190417/https://www2.cio.com.au/article/631142/microsoft-previews-quantum-computing-development-kit/ |url-status=dead }}</ref>
==Documentation and resources== Currently, the resources available for Q# are scarce, but the official documentation is published: [https://docs.microsoft.com/en-us/quantum/?view=qsharp-preview Microsoft Developer Network: Q#]. [https://github.com/Microsoft/Quantum/ 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, called [https://web.archive.org/web/20181119064628/https://codeforces.com/msqs2018 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: [https://github.com/Microsoft/QuantumKatas 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 {{Code|namespace}} for code isolation * All statements end with a {{Code|;}} * Curly braces are used for statements of scope * Single line comments are done using {{Code|//}} * Variable data types such as {{Code|Int}} {{Code|Double}} {{Code|String}} and {{Code|Bool}} are similar, although capitalised (and Int is 64-bit)<ref>{{Cite web|url=https://docs.microsoft.com/en-us/quantum/user-guide/language/types|title=Types in Q# - Microsoft Quantum|website=docs.microsoft.com|date=27 July 2022 }}</ref> * Qubits are allocated and disposed inside a {{Code|using}} block. * Lambda functions are defined using the <code>=></code> operator. * Results are returned using the {{Code|return}} keyword.
===Similarities with F#=== * Variables are declared using either {{Code|let}} or {{Code|mutable}}<ref name=":1" /> * First-order functions * Modules, which are imported using the {{Code|open}} keyword * The datatype is declared after the variable name * The range operator {{Code|..}} * {{Code|for … in}} loops * Every operation/function has a return value, rather than {{Code|void}}. Instead of {{Code|void}}, an empty Tuple {{Code|()}} is returned. * Definition of record datatypes (using the {{Code|newtype}} keyword, instead of {{Code|type}}).
===Differences=== * Functions are declared using the {{Code|function}} keyword * Operations on the quantum computer are declared using the {{Code|operation}} keyword * Lack of multiline comments * Asserts instead of throwing exceptions * Documentation is written in Markdown instead of XML-based documentation tags
==Example== {{Over-quotation|section|date=January 2025}} The following source code is a multiplexer from the official Microsoft Q# library repository.
<syntaxhighlight lang="fsharp"> // Copyright (c) Microsoft Corporation. // Licensed under the MIT License.
namespace Microsoft.Quantum.Canon { open Microsoft.Quantum.Intrinsic; open Microsoft.Quantum.Arithmetic; open Microsoft.Quantum.Arrays; open Microsoft.Quantum.Diagnostics; open Microsoft.Quantum.Math;
/// # Summary /// Applies a multiply-controlled unitary operation $U$ that applies a /// unitary $V_j$ when controlled by n-qubit number state $\ket{j}$. /// /// $U = \sum^{N-1}_{j=0}\ket{j}\bra{j}\otimes V_j$. /// /// # Input /// ## unitaryGenerator /// A tuple where the first element `Int` is the number of unitaries $N$, /// and the second element `(Int -> ('T => () is Adj + Ctl))` /// is a function that takes an integer $j$ in $[0,N-1]$ and outputs the unitary /// operation $V_j$. /// /// ## index /// $n$-qubit control register that encodes number states $\ket{j}$ in /// little-endian format. /// /// ## target /// Generic qubit register that $V_j$ acts on. /// /// # Remarks /// `coefficients` will be padded with identity elements if /// fewer than $2^n$ are specified. This implementation uses /// $n-1$ auxiliary qubits. /// /// # References /// - [ *Andrew M. Childs, Dmitri Maslov, Yunseong Nam, Neil J. Ross, Yuan Su*, /// arXiv:1711.10980](https://arxiv.org/abs/1711.10980) operation MultiplexOperationsFromGenerator<'T>(unitaryGenerator : (Int, (Int -> ('T => Unit is Adj + Ctl))), index: LittleEndian, target: 'T) : Unit is Ctl + Adj { let (nUnitaries, unitaryFunction) = unitaryGenerator; let unitaryGeneratorWithOffset = (nUnitaries, 0, unitaryFunction); if Length(index!) == 0 { fail "MultiplexOperations failed. Number of index qubits must be greater than 0."; } if nUnitaries > 0 { let auxiliary = []; Adjoint MultiplexOperationsFromGeneratorImpl(unitaryGeneratorWithOffset, auxiliary, index, target); } }
/// # Summary /// Implementation step of `MultiplexOperationsFromGenerator`. /// # See Also /// - Microsoft.Quantum.Canon.MultiplexOperationsFromGenerator internal operation MultiplexOperationsFromGeneratorImpl<'T>(unitaryGenerator : (Int, Int, (Int -> ('T => Unit is Adj + Ctl))), auxiliary: Qubit[], index: LittleEndian, target: 'T) : Unit { body (...) { let nIndex = Length(index!); let nStates = 2^nIndex;
let (nUnitaries, unitaryOffset, unitaryFunction) = unitaryGenerator;
let nUnitariesLeft = MinI(nUnitaries, nStates / 2); let nUnitariesRight = MinI(nUnitaries, nStates);
let leftUnitaries = (nUnitariesLeft, unitaryOffset, unitaryFunction); let rightUnitaries = (nUnitariesRight - nUnitariesLeft, unitaryOffset + nUnitariesLeft, unitaryFunction);
let newControls = LittleEndian(Most(index!));
if nUnitaries > 0 { if Length(auxiliary) == 1 and nIndex == 0 { // Termination case
(Controlled Adjoint (unitaryFunction(unitaryOffset)))(auxiliary, target); } elif Length(auxiliary) == 0 and nIndex >= 1 { // Start case let newauxiliary = Tail(index!); if nUnitariesRight > 0 { MultiplexOperationsFromGeneratorImpl(rightUnitaries, [newauxiliary], newControls, target); } within { X(newauxiliary); } apply { MultiplexOperationsFromGeneratorImpl(leftUnitaries, [newauxiliary], newControls, target); } } else { // Recursion that reduces nIndex by 1 and sets Length(auxiliary) to 1. let controls = [Tail(index!)] + auxiliary; use newauxiliary = Qubit(); use andauxiliary = Qubit[MaxI(0, Length(controls) - 2)]; within { ApplyAndChain(andauxiliary, controls, newauxiliary); } apply { if nUnitariesRight > 0 { MultiplexOperationsFromGeneratorImpl(rightUnitaries, [newauxiliary], newControls, target); } within { (Controlled X)(auxiliary, newauxiliary); } apply { MultiplexOperationsFromGeneratorImpl(leftUnitaries, [newauxiliary], newControls, target); } } } } } adjoint auto; controlled (controlRegister, ...) { MultiplexOperationsFromGeneratorImpl(unitaryGenerator, auxiliary + controlRegister, index, target); } adjoint controlled auto; }
/// # Summary /// Applies multiply-controlled unitary operation $U$ that applies a /// unitary $V_j$ when controlled by n-qubit number state $\ket{j}$. /// /// $U = \sum^{N-1}_{j=0}\ket{j}\bra{j}\otimes V_j$. /// /// # Input /// ## unitaryGenerator /// A tuple where the first element `Int` is the number of unitaries $N$, /// and the second element `(Int -> ('T => () is Adj + Ctl))` /// is a function that takes an integer $j$ in $[0,N-1]$ and outputs the unitary /// operation $V_j$. /// /// ## index /// $n$-qubit control register that encodes number states $\ket{j}$ in /// little-endian format. /// /// ## target /// Generic qubit register that $V_j$ acts on. /// /// # Remarks /// `coefficients` will be padded with identity elements if /// fewer than $2^n$ are specified. This version is implemented /// directly by looping through n-controlled unitary operators. operation MultiplexOperationsBruteForceFromGenerator<'T>(unitaryGenerator : (Int, (Int -> ('T => Unit is Adj + Ctl))), index: LittleEndian, target: 'T) : Unit is Adj + Ctl { let nIndex = Length(index!); let nStates = 2^nIndex; let (nUnitaries, unitaryFunction) = unitaryGenerator; for idxOp in 0..MinI(nStates,nUnitaries) - 1 { (ControlledOnInt(idxOp, unitaryFunction(idxOp)))(index!, target); } }
/// # Summary /// Returns a multiply-controlled unitary operation $U$ that applies a /// unitary $V_j$ when controlled by n-qubit number state $\ket{j}$. /// /// $U = \sum^{2^n-1}_{j=0}\ket{j}\bra{j}\otimes V_j$. /// /// # Input /// ## unitaryGenerator /// A tuple where the first element `Int` is the number of unitaries $N$, /// and the second element `(Int -> ('T => () is Adj + Ctl))` /// is a function that takes an integer $j$ in $[0,N-1]$ and outputs the unitary /// operation $V_j$. /// /// # Output /// A multiply-controlled unitary operation $U$ that applies unitaries /// described by `unitaryGenerator`. /// /// # See Also /// - Microsoft.Quantum.Canon.MultiplexOperationsFromGenerator function MultiplexerFromGenerator(unitaryGenerator : (Int, (Int -> (Qubit[] => Unit is Adj + Ctl)))) : ((LittleEndian, Qubit[]) => Unit is Adj + Ctl) { return MultiplexOperationsFromGenerator(unitaryGenerator, _, _); }
/// # Summary /// Returns a multiply-controlled unitary operation $U$ that applies a /// unitary $V_j$ when controlled by n-qubit number state $\ket{j}$. /// /// $U = \sum^{2^n-1}_{j=0}\ket{j}\bra{j}\otimes V_j$. /// /// # Input /// ## unitaryGenerator /// A tuple where the first element `Int` is the number of unitaries $N$, /// and the second element `(Int -> ('T => () is Adj + Ctl))` /// is a function that takes an integer $j$ in $[0,N-1]$ and outputs the unitary /// operation $V_j$. /// /// # Output /// A multiply-controlled unitary operation $U$ that applies unitaries /// described by `unitaryGenerator`. /// /// # See Also /// - Microsoft.Quantum.Canon.MultiplexOperationsBruteForceFromGenerator function MultiplexerBruteForceFromGenerator(unitaryGenerator : (Int, (Int -> (Qubit[] => Unit is Adj + Ctl)))) : ((LittleEndian, Qubit[]) => Unit is Adj + Ctl) { return MultiplexOperationsBruteForceFromGenerator(unitaryGenerator, _, _); }
/// # Summary /// Computes a chain of AND gates /// /// # Description /// The auxiliary qubits to compute temporary results must be specified explicitly. /// The length of that register is `Length(ctrlRegister) - 2`, if there are at least /// two controls, otherwise the length is 0. internal operation ApplyAndChain(auxRegister : Qubit[], ctrlRegister : Qubit[], target : Qubit) : Unit is Adj { if Length(ctrlRegister) == 0 { X(target); } elif Length(ctrlRegister) == 1 { CNOT(Head(ctrlRegister), target); } else { EqualityFactI(Length(auxRegister), Length(ctrlRegister)); let controls1 = ctrlRegister[0..0] + auxRegister; let controls2 = Rest(ctrlRegister); let targets = auxRegister + [target]; ApplyToEachA(ApplyAnd, Zipped3(controls1, controls2, targets)); } } } </syntaxhighlight>
==References== {{Reflist}}
==External links== *{{Official website|https://docs.microsoft.com/en-us/azure/quantum/}} *{{GitHub|microsoft/qsharp-language}} (now deprecated) *{{GitHub|microsoft/qsharp}} (Modern QDK repository)
{{quantum computing}} {{Common Language Infrastructure}} {{Microsoft FOSS}} {{Microsoft development tools}}
Category:Microsoft free software Category:Microsoft programming languages Category:Quantum programming Category:Programming languages created in 2017 Category:Software using the MIT license