Bang-Bang control of a qubit coupled to a quantum critical spin bath
  We analytically and numerically study the effects of pulsed control on the decoherence of a qubit coupled to a quantum spin bath. When the environment is critical, decoherence is faster and we show that the control is relatively more effective. Two coupling models are investigated, namely a qubit coupled to a bath via a single link and a spin star model, yielding results that are similar and consistent. 
Davide Rossini, Paolo Facchi, Rosario Fazio, Giuseppe Florio, Daniel   A. Lidar, Saverio Pascazio, Francesco Plastina, Paolo...