At time there are talks about quantum computers and lot of talks and discussion on its exponential speed. But studying in some more details it makes reference to "Heisenberg uncertainty principle", which simply says that either position or momentum can be calculated for any electron. If we already know the limitation, then in which direction this research is going?
Quantum Computers can process information in a different way then classical computers the main isuues is how to use classical input to "convince" the qbit to process what we are asking and then give an answer that we can use in a positive way. Research is progressing towards a quantum level interface that can account for decoherence between the information we give and a understandable answer coming out.
In other words the language barrier between classical people and quantum interpretation. There is no technical limitation to QC's at this time only a limit of our ability to minipulate qbit s the do What we want.
http://www.cra.org/ccc/docs/init/Quantum_Computing.pdf is a PDF document link to the currently imposed limitations of quantum computers.