High Fidelity Single Qubit Operations using Pulsed EPR
  Systematic errors in spin rotation operations using simple RF pulses place severe limitations on the usefulness of the pulsed magnetic resonance methods in quantum computing applications. In particular, the fidelity of quantum logic operations performed on electron spin qubits falls well below the threshold for the application of quantum algorithms. Using three independent techniques, we demonstrate the use of composite pulses to improve this fidelity by several orders of magnitude. The observed high-fidelity operations are limited by pulse phase errors, but nevertheless fall within the limits required for the application of quantum error correction. 
John J. L. Morton, Alexei M. Tyryshkin, Arzhang Ardavan, Kyriakos   Porfyrakis, S. A. Lyon, G. Andrew D. Briggs