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Q# and the Azure Quantum Development Kit

What is it​

Q# is a high-level, strongly typed quantum programming language created by Microsoft, paired with the Azure Quantum Development Kit (QDK). Unlike most frameworks, which are Python libraries, Q# is its own language designed specifically to express quantum algorithms, with classical control flow handled around quantum operations. You write Q# directly or drive it from Python via the qsharp package.

The modern QDK is a from-scratch rewrite (compiled to WebAssembly) that runs in VS Code, in Jupyter, and from Python. It includes a state-vector simulator, the Azure Quantum Resource Estimator (a standout feature for estimating the qubits and runtime a fault-tolerant algorithm would need), and submission to hardware through Azure Quantum.

Install​

pip install qsharp

For the full authoring experience, install the Azure Quantum Development Kit extension in VS Code, which provides syntax support, the local simulator, and resource estimation. The Python qsharp package lets you run Q# inline from notebooks and scripts.

Hello Quantum​

A Bell state 12(∣00⟩+∣11⟩)\frac{1}{\sqrt{2}}\left( \lvert 00 \rangle + \lvert 11 \rangle \right) written in Q#:

import Std.Diagnostics.*;

operation BellState() : (Result, Result) {
    // Allocate two qubits, initialized to |0>
    use (q0, q1) = (Qubit(), Qubit());

    H(q0);          // superposition
    CNOT(q0, q1);   // entangle

    // Measure and reset before release
    let r0 = M(q0);
    let r1 = M(q1);
    ResetAll([q0, q1]);
    return (r0, r1);
}

You can run this from Python with the modern QDK:

import qsharp

qsharp.eval(open("BellState.qs").read())
results = qsharp.run("BellState()", shots=1024)
print(results)   # pairs are correlated: (Zero, Zero) or (One, One)

Every shot returns matching results — both Zero or both One — confirming the qubits are entangled.

Strengths & use cases​

  • Algorithm-first language. Q#'s type system and abstractions are tailored to quantum logic, which is excellent for teaching and for expressing complex algorithms cleanly.
  • Resource estimation. The Azure Quantum Resource Estimator projects the physical/logical qubit counts and runtime for fault-tolerant implementations — useful well before such hardware exists.
  • Cloud hardware. Azure Quantum gives access to multiple vendors (IonQ, Quantinuum, Rigetti) behind one service.
  • Tooling. Tight VS Code integration with debugging, simulation, and circuit visualization.

Ecosystem​

  • Azure Quantum — cloud service for running Q# (and OpenQASM/Qiskit) on partner hardware.
  • Azure Quantum Resource Estimator — fault-tolerant resource analysis.
  • qsharp Python package — run Q# from Python/Jupyter.
  • OpenQASM and Qiskit interop — submit circuits authored in other formats through Azure Quantum.

Resources​

When you are ready to write Q#, see the labs; to plan your path, see the roadmaps.