On the universality of almost every quantum logic gate
Nik Weaver · Journal of Mathematical Physics · 2000
Lloyd [Phys. Rev. Lett. 75, 346 (1995)] showed that almost every quantum logic gate is universal in the sense that it can be used to approximate any unitary transformation. The argument relied on a more general fact whose proof was not given in detail. We give a complete proof of this more general fact.