Initial state preparation demo

[Chiffafox]

Title:

Initial state preparation for quantum chemistry

Summary:

This demo is explaining the concept of an initial state -- a primer for a quantum algorithm that improves its chances of success specifically for the task of obtaining the ground-state energy of a molecule. It showcases the newly built functionality in PennyLane for importing outputs from sophisticated computational chemistry methods to initialize better initial states. Finally, it shows how the choice of initial state affects the execution of VQE on a simple molecule, demonstrating the importance of initial state for quantum algorithms and that this can of algorithms R&D can be now performed in PennyLane.

Relevant references:

Possible Drawbacks:

Related GitHub Issues:

[github-actions]

Thank you for opening this pull request.

You can find the built site at this link.

Deployment Info:

• Pull Request ID: 950
• Deployment SHA: 0620b9099dd3e93531805eb8c6afa59571219a04
  (The Deployment SHA refers to the latest commit hash the docs were built from)

Note: It may take several minutes for updates to this pull request to be reflected on the deployed site.

[alvaro-at-xanadu]

Amazing improvement! Loved the plot at the end and the comparison between the convergence rates. Code is also much more friendly to read 🚀

Let me know if the suggestion for fixing the rendering error works. If it does, I'll approve 🎉

[KetpuntoG]

Great work here! Ready to merge, I'll take care of it tomorrow 😊

[soranjh]

Thanks @Chiffafox, left a mall comment on splinting the VQE code block.

[soranjh]

Great job @Chiffafox, left one final comment in Conclusions.