New proposed tutorial on quantum phase transitions

[DamianPope]

Hello,
We’ve been using PennyLane (PL) for four years and love it. This tutorial came about when we realized that many researchers were interested in phase transitions and quantum computers. However, some of them don’t have backgrounds in quantum computing. We’d love for you to consider this as a PL demo.

This is only our second PR for PL. So, we hope that we followed the instructions correctly. Many thanks. Damian Pope & Tirth Shah.

Title: Seeing Quantum Phase Transitions with Quantum Computers

Summary
A phase transition is when some property of a physical system changes abruptly. A quantum phase transition is when this happens due to quantum fluctuations. Quantum phase transitions are widely studied in condensed matter physics and cosmology. Many recent papers and current research are investigating them.

This tutorial introduces the concept of a quantum phase transition and walks through the PennyLane code for simulating three well-known quantum phase transitions with a quantum computer. It uses PennyLane’s qubit.lighting simulator.

Relevant references
M. Heyl, A. Polkovnikov, and S. Kehrein, “Dynamical Quantum Phase Transitions in the Transverse-Field Ising Model”, Phys. Rev. Lett. 110, 135704 (2013)
https://arxiv.org/abs/1206.2505

Hashizume, Tomohiro 2022, “Dynamical phase transitions in the two-dimensional transverse-field Ising model”, Phys. Rev. Research 4, 013250 (2022) https://arxiv.org/abs/1811.09275

Reza Haghshenas et al. “Probing critical states of matter on a digital quantum computer” Phys. Rev. Lett. 133, 266502 (2024) arXiv:2305.01650 [quant-ph]

Possible Drawbacks:
The demo doesn’t directly relate to a recent paper. (But it is indirectly related to many recent papers.)

Related GitHub Issues:
N/A

If you are writing a demonstration, please answer these questions to facilitate the marketing process.
GOALS — Why are we working on this now?

Quantum phase transitions are a widely studied topic in multiple fields of physics. However, there are many cases where both analytic and classical computing techniques struggle to generate solutions. Quantum computers may be able to help where these other techniques fail. Simulating quantum phase transitions on quantum computers is currently a hot topic. Recently, there have been many papers on it including, for example, this Nature paper from February: https://www.nature.com/articles/s41567-024-02765-w

There are many researchers who are interested in quantum phase transitions but don’t have a background in quantum computing. An introductory tutorial on quantum phase transitions could be beneficial to these individuals.

PennyLane is well-suited to efficiently programming quantum computers to simulate quantum phase transitions. Its qml.spin module is especially useful for simulating phase transitions in the Ising model.

AUDIENCE — Who is this for?
Researchers interested in quantum phase transitions.
Quantum computing researchers who’d like to learn about quantum phase transitions.
Educators teaching phase transitions and condensed matter physics.

KEYWORDS — What words should be included in the marketing post?
quantum phase transition, condensed matter physics, many-body physics, Ising model, transverse Ising model

Which of the following types of documentation is most similar to your file?
(more details here note this requires a Xanadu email to view)
Tutorial
Demo -check
How-to

Notes:
The suggested thumbnail is a graphic showing an ice cube (i.e. solid water) melting into liquid water. This is a familiar visual cue for the general idea of a phase transition.

I suggest that the hero image conveys the idea of a group of qubits changing from one state (|0>) to another very different state (0> + |1>). This is a visual representation of a simple quantum phase transition. Below is a rough sketch of it.

[github-actions]

Your preview is ready 🎉!

You can view your changes here

[DamianPope]

Hello! Am I meant to flag that this PR is done & ready for review? This is our first demo submission. So, we’re unsure of the process.

Should we be requesting a review? Or tagging someone? I noticed that PennyLane’s website says:
“…and finally submit a pull request in which you can tag our team for review.”
https://pennylane.ai/qml/demos_submission

Before submitting this PR, we were in communication with someone on the PL team. We tried to follow all the other guidelines.

We’ve seen many recent papers on quantum phase transitions (the subject of our demo) & hope that our tutorial will be useful to a wide range of researchers. We also think that it links to & supports this recent PL tutorial: https://pennylane.ai/qml/demos/tutorial_annni

Many thanks.

Damian Pope & Tirth Shah

[CatalinaAlbornoz]

Hi @DamianPope , thanks for submitting this demo and for letting us know that it's ready for review!

It's true that the guidelines currently aren't super clear on how to indicate that it's ready. Thanks for the feedback.

For now rest assured that we've got your demo on our radar and will be assigning someone for review soon.

Do you have a specific urgency for this to get published? We have several demos in the pipeline so this can help us prioritize.

[DamianPope]

Thanks @CatalinaAlbornoz Not a problem, just wanted to check. No urgency with getting it published. Thanks for asking.

Damian & Tirth

[daniela-angulo]

Hi Damian, thanks for this submission!
Things had been pretty hectic for the content team lately, but now settling down. I will start reviewing this demo next week.
Expect to see the review then.
Have a nice week 😄

[DamianPope]

Hi Daniela,

Thank you! That's great news. Glad that things are settling down. We'll try our best to take in any feedback & make changes.
Have a nice week too.

Damian Pope & Tirth Shah

[daniela-angulo]

I started by switching the files to new demo pipeline (adding it to demonstrations_v2) so it can generate a preview. Now you can check the preview and edit accordingly.
The demo reads well, it is quite clear and gives interesting details!
I added a some comments for you to address and I'll review again after you are done with them.
Thanks for your contribution!

[DamianPope]

Thanks so much @daniela-angulo for your kinds words & such a detailed & helpful review. Much appreciated! We're working our way through your comments. We hope to get back to you shortly with a revised (and improved) demo. Thanks again.
Damian Pope & Tirth Shah.

[DamianPope]

Hello! I just have one question about the new demonstrations_v2 process. The documentation says that I need to add a requirements.in file. But, our demo doesn't need any special libraries like scipy etc.
Should I add a blank requirements.in file? Or do something else? Thanks!

[daniela-angulo]

Hi @DamianPope
No, at the moment, you don't need to do anything else. Since the demo doesn't need any other libraries, it is fine as is.
You can even check the preview in the link provided above by the git-hub bot. It is rendering well.
Let me take another look at it, with the changes and such and I think we will be almost done. Thanks!

[DamianPope]

Thanks @daniela-angulo ! That helps. And thanks for offering to look at our changes.

Damian

[DamianPope]

Thanks @daniela-angulo for all your changes. Thanks for cleaning up my demo & improving the language. Much better now.