I am wondering if anyone knows of any resources that take an elementary, undergraduate-friendly approach to the theorem, due (I believe) to Deutsch and Divincenzo, that two-qubit gates are universal for quantum computation. In other words, any unitary transformation $U \in SU(2^n)$ can be approximated arbitrarily well by a finite sequence $U = U_1 \cdots U_r$ of unitary transformations, each with the property $U_i = I_s \otimes U'_i \otimes I_{n-s-2}$, where $U'_i \in SU(2)$. I am aware that one proof is given in Nielsen & Chuang, and it is pitched at approximately the level I have in mind, but I would prefer a more streamlined source, if one exists.
Maybe these two requirements are contradictory. More streamlined sources, including Deutsch's and Divincenzo's original papers, may necessarily assume a familiarity with quantum mechanics and computing theory that make them uninviting for undergraduates. But if anyone knows of any sources that start from a place similar to Nielsen & Chuang but focus on universal quantum gate sets, I would be very interested. Sources may include textbooks, articles, and online notes.
It would be especially nice if a source related the result to geometric or Lie-theoretic properties of $SU(n)$, but that is absolutely not a necessity.