Tutorial qrack

[WrathfulSpatula]

Title: The Qrack device back end (with Catalyst)

Summary: In this tutorial you will learn how to use the Qrack device back end for PennyLane and Catalyst, and you'll learn certain suggested cases of use where Qrack might particularly excel at delivering lightning-fast performance or minimizing required memory resources.

Relevant references: https://github.com/unitaryfund/qrack https://github.com/unitaryfund/pyqrack https://arxiv.org/abs/2304.14969

Possible Drawbacks: Not all users might have Catalyst installed, and this tutorial will require Catalyst v0.7 or later.

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If you are writing a demonstration, please answer these questions to facilitate the marketing process.

• GOALS — Why are we working on this now?

  The Catalyst and Unitary Fund teams are working together to update the Qrack PennyLane device back end (based on open-source code reuse from the Qulacs device and original work with Qrack and Catalyst) to make use of the Catalyst compiler and potentially achieve leading performance on a wide range of qml.qnode subroutine qubit widths and applications. Notably, Qrack automatically switches between CPU-based and GPU-used based simulation methods as appropriate to maximize overall performance, whether circuits are wide enough to benefit from thousands of parallel work items in a job dispatched to a GPU. The Qrack device back end is also open source and can serve as an example or basis for other simulator device back ends that may reuse its code.

• AUDIENCE — Who is this for?

  The potential audience includes researchers, educators, students, hobbyists, and anyone with an interest in faster and more efficient quantum computer simulation in PennyLane.

• KEYWORDS — What words should be included in the marketing post?

  GPU, high-performance computing (HPC), hybrid CPU/GPU, near-Clifford simulation, quantum binary decision diagrams (QBDD), vendor-agnostic GPU support (OpenCL), optional CUDA

• Which of the following types of documentation is most similar to your file? (more details here)

• [ ] Tutorial

• [x] Demo

• [ ] How-to

[josh146]

Thanks for submitting this @WrathfulSpatula! Note: if you make this PR against the dev branch of the QML repo, it will automatically use the latest development version of Catalyst, which may allow the checks to pass.

[WrathfulSpatula]

@josh146 I don't know why rebasing had this effect on this PR, but I'm closing it in favor of copying the single tutorial file into dev branch.