Incorporating Wavefunction and DifferentialOperator into representations

This post is a bit late because I’ve been experiencing some computer troubles recently.

Since my last post, the represent branch has been merged into sympy master! There are still some issues with representing continuous bases that need to be ironed out, so I have started a represent2 branch to deal with some of these changes.

The first commits in the branch are some simple fixes to docstrings and cleanup of the interfaces of Wavefunction (Wf) and DifferentialOperator (DO). Of note are the addition of an _eval_expand to Wf and DO, so that we can do simplifications like expand(Wavefunction((x+y)**2, x, y)) == Wavefunction(x**2, x, y) + Wavefunction(y**2, x, y) + Wavefunction(2*x*y, x, y).

The biggest tasks for represent2 are to incorporate the new Wf and DO classes into the internal represent logic of classes in quantum. Another big task is to simplify the logic of represent. In particular, rep_innerproduct and rep_expectation will become helper functions rather than being called from the main represent logic. This simplifies the main logic, but retains these methods to be called from the internal _represent methods. This is important because these functions know about proper indexing to form representations in these very standard forms, and this means we don’t have to reproduce that logic internally.

Both of these tasks are proving to be quite tricky and time consuming. I hope to have them done in the next couple of days. If that is the case, I expect to be able to rapidly move on to implementing coordinate systems and finally getting some example textbook quantum systems up and running. With only a few weeks of GSoC left, I’ll have to work extra hard to make that happen. Modifying the represent logic is taking much longer than expected, but we’re dealing with very complicated logic here and we want to make sure its robust. I’m confident, though, that I can have a nice finished product by the end of GSoC.

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One Response

  1. Hi,

    I did not follow your work in detail nor the whole quantum stuff in sympy. But does this post mean that we can express raising/lowering
    operators symbolically? For analytical wavefunctions? (I do not speak
    about 2nd quantization which is already there I think but about the harmonic oscillator. And also more complex but similar wavefunctions I’m working on.)

    Raoul

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