Practical approximation of single-qubit unitaries by single-qubit   quantum Clifford and T circuits
  We present an algorithm, along with its implementation that finds T-optimal approximations of single-qubit Z-rotations using quantum circuits consisting of Clifford and T gates. Our algorithm is capable of handling errors in approximation down to size $10^{-15}$, resulting in optimal single-qubit circuit designs required for implementation of scalable quantum algorithms. Our implementation along with the experimental results are available in the public domain. 
Vadym Kliuchnikov, Dmitri Maslov, and Michele Mosca
quant-ph cs.ET