Coherence time in the presence of dipole–dipole interactions. We plotted the 1/ e coherence time measured with spin echo as a function of the effective laboratory-frame dipole moment, tuned by changing the states used in the spin-echo sequence. The combinations used were (i) 1/sqrt(2)(|1> + |-2>) , (ii) 1/sqrt(2)(|0> + |-1>) and (iii) 1/sqrt(2)(|0> + |1>) . The fringe contrast as a function of time for each state combination is shown in the top-right inset. The wavefunctions are illustrated with (i) and (ii) yielding dipoles rotating around the quantization axis and (iii) resulting in a dipole that oscillates up and down. The bottom-left inset shows the coherence time plotted as a function of the inverse of the dipole–dipole interaction strength proportional to 1/ d 2 . Error bars in all plots indicate 1 sigma standard error in the measurements, and the 1 sigma uncertainties in the fits and simulations are shown by the shaded regions.
