support for multiple toffoli gate decompositions

[alexandrupaler]

There are various (relative phase) Toffoli gate decompositions, each having its own advantage with respect to (at least) quantum arithmetic [1]. It would be great if Qualtran would support various Toffoli decompositions.

[1] https://arxiv.org/pdf/2101.04764.pdf

[mpharrigan]

Thanks for flagging this. I know @NoureldinYosri has thought about the best way to toggle between different decompositions.

[mpharrigan]

In the standard library of bloqs, we're going to make toffoli a "leaf bloq" #873 , but these circuits can be added as additional information. And there's been a long-time discussion about whether we need different toffolis for if one does or does not care about phases