I recently read a paper, published last year, which suggests that the qubit concept is problematic and that a different processing model is needed for quantum computing:

On The Fundamental Flaws of Qubit Concept for General Purpose Quantum Computing

http://www.ijesi.org/papers/Vol%283%2910/F031059070.pdf

See also:

Quantum computing circuits

http://www.google.com/patents/US20130057314