Qiskit-terra: Jupyter Notebook: Stretched Bloch and Q-Spheres

[splch]

Information

• Qiskit Terra version: 14.2
• Matplotlib version: 3.3.0
• Python version: 3.7.7
• Operating system: macOS

What is the current behavior?

When I create a Bloch or Q-Sphere, the drawing displayed is horizontally stretched.

Steps to reproduce the problem

1. Open a Jupyter Notebook
2. Type the following into a cell:

from numpy import sqrt
from qiskit.visualization import plot_bloch_multivector

plot_bloch_multivector([1/sqrt(2), 1/sqrt(2)])

1. Run the cell

What is the expected behavior?

I would expect the spheres to be shaped like spheres instead of ellipsoids.

Suggested solutions

Is it possible the backend (matplotlib?) needs to be updated?

[obliviateandsurrender]

What's your matplotlib version? Cause mine is 3.2.2 and Bloch shpere is fine for me.
Additionally, did you try adding %matplotlib inline or infact, try adding figsize param: plot_bloch_multivector([1/sqrt(2), 1/sqrt(2)], figsize=(10,10))?

[splch]

@obliviateandsurrender I'm running matplotlib version 3.3.0 (so this might be a version issue?) and neither figsize=(10,10) nor %matplotlib inline fixed the drawing.

[gschaffner]

I can also replicate the issue with matplotlib 3.3.0 but not with 3.2.2.

Likely due to https://matplotlib.org/3.3.0/users/whats_new.html#axes3d-no-longer-distorts-the-3d-plot-to-match-the-2d-aspect-ratio

[splch]

@gschaffner Do you think creating a default argument for set_box_aspect would fix the distortion?

[e-eight]

Hey, looks like this has not been fixed yet. Mind if I take a look at this?

[splch]

@e-eight yes please do! i hope you can figure it out but let me know if i can help with anything

[e-eight]

Cool. I'll let you know what I find.