# Equatorial plane intersecting a Bloch sphere

I have created a Bloch sphere and I would like to show the equatorial plane intersecting the sphere. I have tried the following but I am sure there is room for improvement.

\documentclass[border=5pt]{standalone}
\usepackage{blochsphere}
\usepackage{tikz-3dplot}
\begin{document}
\begin{blochsphere}[radius = 1.5 cm, tilt = 15, rotation = -45, opacity = 0.20]
% Drawing the equatorial plane
\tdplotsetmaincoords{5}{0}
\tdplotsetrotatedcoords{0}{0}{0}
\begin{scope}[tdplot_rotated_coords]
\draw[fill=blue,opacity=0.2, scale=3] (-0.5,0,-0.5) -- (-1,0,1) -- (1,0,1) -- (0.5,0,-1) -- cycle;
\end{scope}
% Draw the ball and grid
\drawBallGrid[style={opacity=0.5, color = blue, loosely dashed}]{180}{180}
% Axes (X, Y, Z)
\drawStatePolar[axisarrow = true, statewidth = 0.5, scale = 1.50]{x}{90}{90}
\drawStatePolar[axisarrow = true, statewidth = 0.5, scale = 1.50]{y}{90}{00}
\drawStatePolar[axisarrow = true, statewidth = 0.5, scale = 1.15]{z}{00}{00}
\end{blochsphere}
\end{document}


I take that you wish to use tikz-3dplot combined with blochsphere. These packages have different means in order to set the view angles. So one needs to adjust the theta angle in tikz-3dplot to match the projection used by blochsphere.

\documentclass[border=5pt]{standalone}
\usepackage{blochsphere}
\usepackage{tikz-3dplot}
\begin{document}
\begin{blochsphere}[radius = 1.5 cm, tilt = 15, rotation = -45, opacity = 0.20]
% Drawing the equatorial plane
\tdplotsetmaincoords{105}{45}
\tdplotsetrotatedcoords{0}{0}{0}
\begin{scope}[tdplot_main_coords,canvas is xy plane at z=0,on layer=back]
\fill[blue!40,opacity=0.5] (-6,-6) -- (225:1.5) arc(225:45:1.5)
-- (6,6) -- (6,-6) --cycle;
\end{scope}
% Draw the ball and grid
\drawBallGrid[style={opacity=0.5, color = blue, loosely dashed}]{180}{180}
% Axes (X, Y, Z)
\drawStatePolar[axisarrow = true, statewidth = 0.5, scale = 1.50]{x}{90}{90}
\drawStatePolar[axisarrow = true, statewidth = 0.5, scale = 1.50]{y}{90}{00}
\drawStatePolar[axisarrow = true, statewidth = 0.5, scale = 1.15]{z}{00}{00}
\begin{scope}[tdplot_main_coords,canvas is xy plane at z=0,on layer=front]
\fill[blue!40,opacity=0.5] (-6,-6) -- (225:1.5) arc(225:45:1.5)
-- (6,6) -- (-6,6) --cycle;
\end{scope}
\end{blochsphere}
\end{document}


• Nice to see you are back! I was already missing your expertise... :-) Maybe you could have a look here? tex.stackexchange.com/questions/501307/… Thanks a lot in advance! :-) – Dave Jul 25 '19 at 19:11
• @Dave Thanks! But I am not unretiring. There is no protection against rogue users on this site. – user121799 Jul 25 '19 at 22:06
• Yeah, that is unfortunately true. :-( Nevertheless, do you have any ideas how I could solve my issue to get the data from the current table format into the plot? – Dave Jul 28 '19 at 21:13
• Thank you @marmot for the superb answer! Very impressive as usual :) – M. Al Jumaily Jul 30 '19 at 17:55