Adaptive measurement of spin decoherence time $T_{2}$

Spin decoherence time $T_{2}$ is an important parameter in quantum mechanics. In order to estimate it accurately and efficiently, we propose a scheme for spin decoherence time $T_{2}$ estimation of a single spin using adaptive measurement. While the ordinary scheme of measuring $T_{2}$ yield an estimate precision scales with mean-square error $\sim 1/\sqrt{N}$ ($N$ is the number of measurements). We present some simulated measurement which shows that the adaptive scheme, that is, the time between measurements was depended on the prior measurement results, will give a better scaling than MSE.