Quantum arithmetic with the Quantum Fourier Transform
  The Quantum Fourier Transform offers an interesting way to perform arithmetic operations on a quantum computer. We review existing Quantum Fourier Transform adders and multipliers and propose some modifications that extend their capabilities. Among the new circuits, we propose a quantum method to compute the weighted average of a series of inputs in the transform domain. 
Lidia Ruiz-Perez and Juan Carlos Garcia-Escartin
quant-ph