Additional information

• Images
• Videos
• Documents
• Books
• Articles

History

Historically, Microsoft Research had two teams interested in quantum computing: the QuArC team based in Redmond, Washington,⁵ 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.⁶⁷

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.⁸ On December 11, 2017, Microsoft released Q# as a part of the Quantum Development Kit.⁹

At Build 2019, Microsoft announced that it would be open-sourcing the Quantum Development Kit, including its Q# compilers and simulators.¹⁰

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#.¹¹

Bettina Heim currently leads the Q# language development effort.¹²¹³

Usage

Q# is available as a separately downloaded extension for Visual Studio,¹⁴ 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.¹⁵

The Quantum Development Kit includes a quantum simulator capable of running Q# and simulated 30 logical qubits.¹⁶¹⁷

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.¹⁸

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).

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.¹⁹

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, called 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 namespace 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 Int Double String and Bool are similar, although capitalised (and Int is 64-bit)²⁰
• Qubits are allocated and disposed inside a using block.
• Lambda functions are defined using the => operator.
• Results are returned using the return keyword.

Similarities with F#

• Variables are declared using either let or mutable²¹
• First-order functions
• Modules, which are imported using the open keyword
• The datatype is declared after the variable name
• The range operator ..
• for … in loops
• Every operation/function has a return value, rather than void. Instead of void, an empty Tuple () is returned.
• Definition of record datatypes (using the newtype keyword, instead of type).

Differences

• Functions are declared using the function keyword
• Operations on the quantum computer are declared using the operation 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 { 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)); } } }

External links

• Official website
• qsharp-language on GitHub

References

1. QuantumWriter. "The Q# Programming Language". docs.microsoft.com. Retrieved 2017-12-11. https://docs.microsoft.com/en-us/quantum/quantum-qr-intro?view=qsharp-preview ↩

2. "Announcing the Microsoft Quantum Development Kit". Retrieved 2017-12-11. https://cloudblogs.microsoft.com/quantum/2017/12/11/announcing-microsoft-quantum-development-kit/ ↩

3. "Microsoft makes play for next wave of computing with quantum computing toolkit". Ars Technica. 25 Sep 2017. Retrieved 2024-09-04. https://arstechnica.com/gadgets/2017/09/microsoft-quantum-toolkit/ ↩

4. "Quantum Computers Barely Exist—Here's Why We're Writing Languages for Them Anyway". MIT Technology Review. 22 Dec 2017. Retrieved 2024-09-04. https://www.technologyreview.com/2017/12/22/3662/quantum-computers-barely-exist-heres-why-were-writing-languages-for-them-anyway/ ↩

5. "Solving the quantum many-body problem with artificial neural networks". Microsoft Azure Quantum. 15 February 2017. https://cloudblogs.microsoft.com/quantum/2017/02/15/solving-the-quantum-many-body-problem-with-artificial-neural-networks/ ↩

6. Scott Aaronson's blog, 2013, 'Microsoft: From QDOS to QMA in less than 35 years', https://scottaaronson.blog/?p=1471 /wiki/Scott_Aaronson ↩

7. "What are the Q# programming language & QDK? - Azure Quantum". learn.microsoft.com. 12 January 2024. https://learn.microsoft.com/en-us/azure/quantum/overview-what-is-qsharp-and-qdk ↩

8. "Microsoft announces quantum computing programming language". Retrieved 2017-12-14. https://cloudblogs.microsoft.com/quantum/2017/09/26/microsoft-announces-quantum-computing-programming-language/ ↩

9. "Announcing the Microsoft Quantum Development Kit". Retrieved 2017-12-11. https://cloudblogs.microsoft.com/quantum/2017/12/11/announcing-microsoft-quantum-development-kit/ ↩

10. Microsoft is open-sourcing its Quantum Development Kit https://venturebeat.com/2019/05/06/microsoft-open-sourcing-quantum-development-kit/ ↩

11. Krill, Paul (29 Sep 2020). "Microsoft taps LLVM for quantum computing". InfoWorld. Retrieved 2024-09-04. https://www.infoworld.com/article/2260508/microsoft-taps-llvm-for-quantum-computing.html ↩

12. "The Women of QuArC". 30 March 2019. https://devblogs.microsoft.com/qsharp/the-women-of-quarc/ ↩

13. "Intro to Q# - Intro to Quantum Software Development". stem.mitre.org. https://stem.mitre.org/quantum/software-tools/intro-qsharp.html ↩

14. QuantumWriter. "Setting up the Q# development environment". docs.microsoft.com. Retrieved 2017-12-14. https://docs.microsoft.com/en-us/quantum/quantum-installconfig?view=qsharp-preview ↩

15. Coppock, Mark (26 Feb 2018). "Microsoft's quantum computing language is now available for MacOS". Digital Trends. Retrieved 2024-09-04. https://www.digitaltrends.com/computing/microsoft-quantum-computing-q-available-macos-linux/ ↩

16. Akdogan, Erman (23 October 2022). "Quantum computing is coming for finance & crypto". Medium. https://medium.datadriveninvestor.com/quantum-computing-is-coming-for-finance-crypto-b56c0255cb09 ↩

17. Melanson, Mike (16 Dec 2017). "This Week in Programming: Get Quantum with Q Sharp". The New Stack. Retrieved 2024-09-04. https://thenewstack.io/week-programming-get-quantum-q-sharp/ ↩

18. "This Week in Programming: Get Quantum with Q Sharp". The New Stack. 16 December 2017. https://thenewstack.io/week-programming-get-quantum-q-sharp/ ↩

19. "Microsoft previews quantum computing development kit". CIO. https://www2.cio.com.au/article/631142/microsoft-previews-quantum-computing-development-kit/ ↩

20. "Types in Q# - Microsoft Quantum". docs.microsoft.com. 27 July 2022. https://docs.microsoft.com/en-us/quantum/user-guide/language/types ↩

21. QuantumWriter. "The Q# Programming Language". docs.microsoft.com. Retrieved 2017-12-11. https://docs.microsoft.com/en-us/quantum/quantum-qr-intro?view=qsharp-preview ↩