Article Open access Published: 14 February 2012 CMOS-based carbon nanotube pass-transistor logic integrated circuits Li Ding, Zhiyong Zhang, Shibo Liang, Tian Pei, Sheng Wang, Yan Li, Weiwei Zhou ...

The adder looks complicated, but it really is just a half-adder and full-adder piped together in exactly the same way it would be wired up with CMOS or TTL gates. The video below shows it in action.