Fix two latex issues in docs

[Eric-Arellano]

These cause the docs app to crash.

[qiskit-bot]

One or more of the following people are relevant to this code:

• @Qiskit/terra-core

[Eric-Arellano]

The comma is only to make the two equations render more nicely.

[jakelishman]

You might want to put an enforced space after the comma to improve it - probably one of \ or \quad depending on how much you want. I'm fine to just merge if this is already good enough for you.

[jakelishman]

Thanks for this. Any chance you know a simple way to get Sphinx to attempt the renders server side, so we can put the checks in our CI?

For my own website, I run KaTeX deployment-side as part of the page-build operation, but since we're not already running any Node-based stuff here, it'd be a bit of a faff if we had to do that via Node, especially for local contributors.

[Eric-Arellano]

Any chance you know a simple way to get Sphinx to attempt the renders server side, so we can put the checks in our CI?

I don't know of anything off the top of my head, but I added that we should investigate this as part of Qiskit/documentation#2228. I know Kevin Sung had switched Qiskit to Katex with Sphinx, so I'm surprised the Sphinx build pass - I have not yet tried triaging what went wrong. I only just found the issue to begin with.

For what it's worth, qiskit/documentation should have caught this issue much sooner. We have a check that every changed page renders, but it didn't correctly run. That's tracked by Qiskit/documentation#2228. So, I didn't notice the issue until doing an open-source sync in the closed source repository. We recently got the nightly dev docs job working, so qiskit/documentation in theory will catch Latex issues every night. That might be sufficient.

[coveralls]

Pull Request Test Coverage Report for Build 11635261948

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 36 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.004%) to 88.721%

---

Files with Coverage Reduction	New Missed Lines	%
crates/accelerate/src/two_qubit_decompose.rs	1	92.09%
crates/qasm2/src/lex.rs	8	91.98%
crates/circuit/src/circuit_data.rs	27	95.55%

Totals
Change from base Build 11634403304:	0.004%
Covered Lines:	76366
Relevant Lines:	86074

---

💛 - Coveralls

[jakelishman]

KaTeX is also client-side JS-based rendering by default like MathJax, and our Sphinx output is certainly set up for client-side rendering, which is why it's not getting caught here.

Looks like sphinxcontrib-katex does have a way of doing the pre-rendering if Node is installed, so maybe there's a sensible path through. I wouldn't want to do that as part of the actual build, though, since we don't want to be making the HTML rendering decisions in this repo.