How to plot an ellipsoid inside a Bloch sphere

[yes...@gmail.com]

How to plot an ellipsoid inside a Bloch sphere?  We know that we plot Bloch sphere using QuTip in python. But, I wanted to plot an ellipsoid (inside this Bloch sphere) centered on (0,0,1/2) with its minor axis along the z-direction. Do anyone know how to do it?

[Simon Cross]

Hello!

You appear to have asked this question three times (possibly by
accident). I will just reply to this instance. :)

Answering this question fully is somewhat outside the scope of QuTiP,
but one approach you can try is:

1. Supply your own matplotlib axes and figure when creating the Bloch
sphere with Bloch(axes=axes, fig=fig).
2. After calling Bloch.render(), draw whatever extra elements you'd
like to have on the figure.

The matplotlib documentation, https://matplotlib.org/, and Bloch
sphere documentation,
https://qutip.org/docs/latest/apidoc/classes.html#bloch-sphere, might
be helpful in this regard.

If there is a common reason why one might want to draw such an
ellipsoid on the Bloch sphere, we could consider adding a feature that
does this (e.g. Bloch.add_dm) but this is a separate discussion.

- Simon