matplotlib 3.4 has begun issuing some new deprecation warnings against some of the stuff we do in bloch.py.

Simple reproducer from within ipython --matplotlib:

In [1]: import qutip
   ...: b = qutip.Bloch()
   ...: b.add_vectors([0, 1, 0])
   ...: b.render()

produces

/Users/jake/.anaconda3/envs/qutip/lib/python3.9/site-packages/qutip/bloch.py:451: MatplotlibDeprec

#660 introduces defaults for layer stacking, such that the user only need specify QINTERFACE_OPTIMAL if they wish to construct the optimal stack, (or QINTERFACE_OPTIMAL_MULTI). To solve the problem of arbitrary depth of QInterface layer stacking, potentially forever, all constructors should take simply an arbitrary length vector of layer types, via the enum we currently have.

All layers

There currently exists a function schmidt_decomposition.py. Given a vector, the function provides the Schmidt decomposition.

Ideally, this function should include the ability to provide not just the Schmidt decomposition of a vector as input, but be robust enough to handle inputs provided as density matrices as well.

Consulting and enhancing the schmidt_decomposition.py file should be w

Is your feature request related to a problem? Please describe.

Now that we have some foundational testing framework in place, we need to augment it to better catch edge cases as well as prevent regressions or new errors popping up when changes are made in related sections of the code. One way of making the test suite broader and more robust is [Property Based Testing](https://fsharpforfunandpr

Need more tutorials contributed by the community