I had to look up partial trace
<http://en.wikipedia.org/wiki/Partial_trace> (this
is a new concept for me). After reading this I'm inclined to separate Trace
and PartialTrace classes in an effort to optimize/simplify for the common
case (at least the common case as I see it).

The idea of a trace of a tensor product still sounds strange to me. I'm
inclined to call this a tensor contraction. As I said though I'm not
familiar with this specific notion of trace.

On Thu, Jul 12, 2012 at 12:49 PM, Brian Granger <[email protected]> wrote:

> One thing to be aware of is that the general Trace has to be able to
> handle partial traces of tensor products.  This logic is implemented
> in this branch:
>
> https://github.com/sympy/sympy/pull/1396
>
> And is somewhat specialized to the stuff in quantum, although it
> doesn't *depend* on quantum.
>
> Cheers,
>
> Brian
>
>
>
> On Thu, Jul 12, 2012 at 12:33 PM, Matthew Rocklin <[email protected]>
> wrote:
> >> So do you think that the same object should trace over MatrixExpr,
> Matrix,
> >> and the physics classes?  It seems to me that it should.
> >
> >
> > Yes. I think that we can easily write a sufficiently general version of
> > Trace, something like the Transpose object in this branch
> >
> https://github.com/mrocklin/sympy/blob/transpose-decentralize/sympy/matrices/expressions/transpose.py
>
>
>
> --
> Brian E. Granger
> Cal Poly State University, San Luis Obispo
> [email protected] and [email protected]
>

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