We currently use transistors for switching voltage levels which are equivalent to a '1' and a '0'. So the fundamental aspect of current computing are transistors (correct me if this is not so). For quantum computing, are we dealing with single atoms. I would like to know what the equivalent of the transistor would be in the quantum side.

I respect that quantum computing is still in research but I would like to know what is actually being investigated.An abrupt phrase that i would like answered is 'what is so great about quantum computing'?

Thanks!