Quantum Limit on Computational Time and Speed
  We investigate if physical laws can impose limit on computational time and speed of a quantum computer built from elementary particles. We show that the product of the speed and the running time of a quantum computer is limited by the type of fundamental interactions present inside the system. This will help us to decide as to what type of interaction should be allowed in building quantum computers in achieving the desired speed. 
A.K. Pati, S.R. Jain, A. Mitra and R. Ramanna