Dynamical suppression of stochastic dephasing of a qubit

It is shown that the stochastic dephasing of a qubit caused by the random frequency modulation in which the stochastic variable obeys the stationary Gauss-Markov process can be suppressed by applying a sequence of π pulses to the qubit. It is found that the application of around ten π pulses within the correlation time of the stochastic variable is enough to suppress the decoherence of the qubit. The recovery of the entanglement of the Werner state by means of π pulses is also discussed