Effects of Imperfect Gate Operations in Shor's Prime Factorization   Algorithm
  The effects of imperfect gate operations in implementation of Shor's prime factorization algorithm are investigated. The gate imperfections may be classified into three categories: the systematic error, the random error, and the one with combined errors. It is found that Shor's algorithm is robust against the systematic errors but is vulnerable to the random errors. Error threshold is given to the algorithm for a given number $N$ to be factorized. 
Hao Guo, Gui-Lu Long and Yang Sun