Enhancement of spin coherence in a spin-1 Bose condensate by dynamical   decoupling approaches
  We present a theoretical investigation on the enhancement of the spin coherence with periodic, concatenated, or Uhrig dynamical decoupling $N$-pulse sequences in a $^{87}$Rb spin-1 Bose condensate, where the intrinsic dynamical instability in such a ferromagnetically interacting condensate causes spin decoherence and eventually leads to a multiple spatial-domain structure or a spin texture. Our results show that all the three sequences successfully enhance the spin coherence by pushing the wave vector of the most unstable mode in the condensate to a larger value. Among the three sequences with the same number of pulses, the concatenated one shows the best performance in preserving the spin coherence. Interestingly, we find that all the three sequences exactly follow the same enhancement law, $k_- T^{1/2} = c$, with $k_-$ the wave vector of the most unstable mode, $T$ the sequence period, and $c$ a sequence-dependent constant. Such a law between $k_-$ and $T$ is also derived analytically for an attractive scalar Bose condensate subjecting to a periodic dynamical decoupling sequence. 
Bo-Yuan Ning, Jun Zhuang, J.Q.You and Wenxian Zhang
cond-mat.quant-gas