projekter
commented
3 years ago Please always submit some example code, so that I know what you do, expect and what does not work. I tried to reproduce this problem, but for me, it works:
\documentclass{article}
\usepackage[compat=0.4]{yquant}
\usepackage{braket}
\begin{document}
\begin{tikzpicture}
\begin{yquant}
qubit a[3];
h a;
[name=sub]
subcircuit {
qubit q;
[ancilla]
qubit {$\ket0$} r;
qubit s;
cnot q | r;
[name=inner]
cnot r | s;
} (a[1, 2]);
[name=outer]
h a;
\end{yquant}
\draw (sub-0-inner-p0) to[in=20, out=50] (outer-0);
\end{tikzpicture}
\end{document}
Here, TikZ is perfectly able to draw the line between the first positive control (-p0) of the CNOT named inner (so the "local" name within the subcircuit is inner-p0) and the first target register (-0) in the outer circuit (which gives the name outer-0).
To make the step from the inner name inner-p0 to the outer name, you prepend the name of the subcircuit. Maybe here was the problem, and I should probably make this more explicit in the manual. The name of the subcircuit is sub. However, whenever you use a gate - and a subcircuit is a gate, though a pretty special one - and assign a name, then there are lots of possible nodes that could receive the name, which is why yquant introduces all those suffixes. So in general, the name sub will not be the actual name, but sub-0, sub-1, ... for the targets, sub-p0, ... for the positive and sub-n0, ... for the negative controls. So the actual name of your subcircuit is sub-0, not sub. Whenever there is just a single (target|positive control|negative control) present, yquant additionally creates an alias of the zero-suffixed node to the name without the suffix. This is why you can refer to the target of the CNOT as inner-0 or just inner, or its positive control as inner-p0 or just inner-p. However, this aliasing behavior is not aware of the fact that subcircuits are special, it just aliases the "outer" enclosing subcircuit node itself (so the rectangle with the name sub-0 is also available as sub), not all the included nodes (which would potentially be a lot of aliases). Hence, you must always specify the full name. In this case, it is sub-0-inner-p0 (or just sub-0-inner-p).
engeljh
This is probably not a bug, but I don't know how to give a name to a subcircuit so that tikz can access it with (subcircuit name-node name). Tikz says that no shape with that name is available. What do I have to do to properly name the subcircuit? Thanks.