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A tool for classical quantum circuit simulation developed as part of theMunich Quantum Toolkit (MQT).It builds uponMQT Core, which forms the backbone of the MQT.

• Decision-diagram–based circuit simulation:Circuit Simulator—strong (statevector) and weak (sampling), incl. mid‑circuit measurements and resets; Qiskit backends (qasm_simulator andstatevector_simulator).Quickstart •API
• Unitary simulation:Unitary Simulator with an optionalalternative recursive construction for improved intermediate compactness.
• Hybrid Schrödinger–Feynman simulation:Hybrid simulator trading memory for runtime with DD and amplitude modes plus multithreading; also available as a statevector backend.
• Simulation Path Framework:Path-based simulation with strategiessequential,pairwise_recursive,bracket, andalternating.
• Noise-aware simulation:Stochastic and deterministic noise (amplitude damping, depolarization, phase flip; density-matrix mode) for global decoherence and gate errors.
• Qiskit-native API: Provider backends and Primitives (Sampler andEstimator) for algorithm-friendly workflows.API
• Decision-diagram visualization: inspect states/unitaries via Graphviz export; seeCircuit Simulator andUnitary Simulator.
• Standalone CLI: fast C++ executables with JSON output; e.g.,ddsim_simple.
• Efficient and portable: C++20 core with DD engines; prebuilt wheels for Linux/macOS/Windows viaPyPI.

If you have any questions, feel free to create adiscussion or anissue onGitHub.

TheMunich Quantum Toolkit (MQT) is developed by theChair for Design Automation at theTechnical University of Munich and supported by theMunich Quantum Software Company (MQSC).Among others, it is part of theMunich Quantum Software Stack (MQSS) ecosystem, which is being developed as part of theMunich Quantum Valley (MQV) initiative.

Thank you to all the contributors who have helped make MQT DDSIM a reality!

The MQT will remain free, open-source, and permissively licensed—now and in the future.We are firmly committed to keeping it open and actively maintained for the quantum computing community.

To support this endeavor, please consider:

• Starring and sharing our repositories:https://github.com/munich-quantum-toolkit
• Contributing code, documentation, tests, or examples via issues and pull requests
• Citing the MQT in your publications (seeCite This)
• Citing our research in your publications (seeReferences)
• Using the MQT in research and teaching, and sharing feedback and use cases
• Sponsoring us on GitHub:https://github.com/sponsors/munich-quantum-toolkit

MQT DDSIM bundled with the provider and backends for Qiskit is available viaPyPI.

(venv) $ pip install mqt.ddsim

The following code gives an example on the usage:

fromqiskitimportQuantumCircuitfrommqtimportddsimcirc=QuantumCircuit(3)circ.h(0)circ.cx(0,1)circ.cx(0,2)print(circ.draw(fold=-1))backend=ddsim.DDSIMProvider().get_backend("qasm_simulator")job=backend.run(circ,shots=10000)counts=job.result().get_counts(circ)print(counts)

Detailed documentation and examples are available atReadTheDocs.

Building the project requires a C++ compiler with support for C++20 and CMake 3.24 or newer.For details on how to build the project, please refer to thedocumentation.Building (and running) is continuously tested under Linux, macOS, and Windows using thelatest available system versions for GitHub Actions.MQT DDSIM is compatible with allofficially supported Python versions.

Please cite the work that best fits your use case.

When citing the software itself or results produced with it, cite the original DD simulation paper:

@article{zulehner2019advanced,title        ={Advanced Simulation of Quantum Computations},author       ={Zulehner, Alwin and Wille, Robert},year         =2019,journal      ={tcad},volume       =38,number       =5,pages        ={848--859},doi          ={10.1109/TCAD.2018.2834427}}

When discussing the overall MQT project or its ecosystem, cite the MQT Handbook:

@inproceedings{mqt,title        ={The {{MQT}} Handbook: {{A}} Summary of Design Automation Tools and Software for Quantum Computing},shorttitle   ={{The MQT Handbook}},author       ={Wille, Robert and Berent, Lucas and Forster, Tobias and Kunasaikaran, Jagatheesan and Mato, Kevin and Peham, Tom and Quetschlich, Nils and Rovara, Damian and Sander, Aaron and Schmid, Ludwig and Schoenberger, Daniel and Stade, Yannick and Burgholzer, Lukas},year         =2024,booktitle    ={IEEE International Conference on Quantum Software (QSW)},doi          ={10.1109/QSW62656.2024.00013},eprint       ={2405.17543},eprinttype   ={arxiv},addendum     ={A live version of this document is available at \url{https://mqt.readthedocs.io}}}

When citing the underlying methods and research, please reference the most relevant peer-reviewed publications from the list below:

[1]A. Zulehner and R. Wille. Advanced Simulation of Quantum Computations.IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems (TCAD), 2019.

[2]S. Hillmich, I. L. Markov, and R. Wille. Just Like the Real Thing: Fast Weak Simulation of Quantum Computation.InDesign Automation Conference (DAC), 2020.

[3]S. Hillmich, R. Kueng, I. L. Markov, and R. Wille. As Accurate as Needed, as Efficient as Possible: Approximations in DD-based Quantum Circuit Simulation.InDesign, Automation and Test in Europe (DATE), 2021.

[4]L. Burgholzer, H. Bauer, and R. Wille. Hybrid Schrödinger–Feynman Simulation of Quantum Circuits with Decision Diagrams.InIEEE International Conference on Quantum Computing and Engineering (QCE), 2021.

[5]L. Burgholzer, A. Ploier, and R. Wille. Exploiting Arbitrary Paths for the Simulation of Quantum Circuits with Decision Diagrams.InDesign, Automation and Test in Europe (DATE), 2022.

[6]T. Grurl, J. Fuß, and R. Wille. Noise-aware Quantum Circuit Simulation with Decision Diagrams.IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems (TCAD), 2022.

The Munich Quantum Toolkit has been supported by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 101001318), the Bavarian State Ministry for Science and Arts through the Distinguished Professorship Program, as well as the Munich Quantum Valley, which is supported by the Bavarian state government with funds from the Hightech Agenda Bayern Plus.