Support common notations in circuit_to_latex_using_qcircuit

[fedimser]

Is your feature request related to a use case or problem? Please describe.
There are common notations for some gates supported by QCircuit, but Cirq's circuit_to_latex_using_qcircuit doesn't use them. This includes:

• SWAP gate which rendered as rectangle with "SWAP" inside it, instead of two crosses connected by a line.
• Multi-controlled X gate, where some controls are "1" and some are "0". Conventional notation for "0" controls is unfilled circle.

Describe the solution you'd like
Add special handling for common conventional notations (supported by QCircuit) to circuit_to_latex_using_qcircuit.

[optional] Describe alternatives/workarounds you've considered
I wrote a find-and-replace post-processing script which produces desired result in my case:

def process_latex(s):
    s = s.replace('\\multigate{1}{\\text{SWAP}}', '\\qswap')
    s = s.replace('\\ghost{\\text{SWAP}}', '\\qswap\\qwx')
    s = s.replace('\\gate{\\text{@}}','\\control')
    s = s.replace('\\gate{\\text{(0)}}','\\ctrlo{}')
    s = s.replace('\\gate{\\text{X}}','\\targ')
    while '   ' in s:
        s = s.replace('   ', ' ')
    return s

[optional] Additional context (e.g. screenshots)
Example of circuit, its current rendering and desired rendering (which was obtained with a script above):

What is the urgency from your perspective for this issue? Is it blocking important work?
P3

[jay-tau]

I would like to attempt working on this, please.

[jay-tau]

Hi @tanujkhattar @fedimser,

I am still very very keen to work on this issue.
Would it be possible to assign it to me?

Cheers,
Joel

[vtomole]

@jay-tau I've assigned it to you.

[jay-tau]

Hello,
Unfortunately, I am unable to solve the issue. Thank you for giving me a chance to work on this issue.
Hopefully, this can be solved by someone else.

[NikolaiLong]

Hello @vtomole, @pavoljuhas, @fedimser I would like to work on this issue. Could someone please assign it to me.

Initial Completion Estimate ETA: 2/28/25

[NikolaiLong]

I was assigned this issue yesterday; therefore, I am pushing back my eta.

Completion Estimate ETA: 3/7/25

[NikolaiLong]

@fedimser is there a particular name for the diagram that contains all of the gates you've listed to be reformatted? For naming the testcase.

[NikolaiLong]

Successfully recreated desired circuit in testcase, does this look accurate @fedimser?

Will now begin work on circuit_to_latex_using_qcircuit method.

Spacing discrepancies addressed with the postprocessing function will most likely not be an issue after large swap boxes are not in use anymore.

[fedimser]

@NikolaiLong, the circuit is just an example, it has no particlar name.

[NikolaiLong]

Debugging of failing testcase complete -

• Modifications required to convert_text_diagram_info_to_qcircuit_diagram_info() for the \targ \control \ctrlo{} issues.
• Modifications required to multigate_qcircuit_diagram_info() to fix the multigate/swap/ ghost/swap issues.

ETA: On Track for 3/7/2025

[NikolaiLong]

I've been much busier with work this week than anticipated, pushing eta back:

Updated Completion ETA: 3/14/2025

[NikolaiLong]

All text conversions have been resolved

Will finish pdf validation tomorrow and hopefully submit a PR before Cirq-Sync on Wednesday.

[NikolaiLong]

PDF generation is accurate - testcase still needs additional validations added before this task is complete.

[NikolaiLong]

All tests passing locally, pdf test is out of scope for this issue and has been left commented out.
New PR Raised: #7151

[NikolaiLong]

I apologize for the in-activity on this issue. I have had to study for the past month and will need continue for potentially a couple months. I will try to work in some time to continue development of this solution in my free time.