We show that observations of high-redshift Ly \alpha emitters ( LAEs ) have the potential to provide definitive evidence for reionization in the near future .
Using 200 Mpc radiative transfer simulations , we calculate the effect that patchy reionization has on the line profile , on the luminosity function , and , most interestingly , on the clustering of emitters for several realistic models of reionization .
Reionization increases the measured clustering of emitters , and we show that this enhancement would be essentially impossible to attribute to anything other than reionization .
Our results motivate looking for the signature of reionization in existing LAE data .
We find that for stellar reionization scenarios the angular correlation function of the 58 LAEs in the Subaru Deep Field z = 6.6 photometric sample is more consistent with a fully ionized universe ( mean volume ionized fraction \bar { x } _ { i } \approx 1 ) than a universe with \bar { x } _ { i } < 0.5 at > 2 - \sigma confidence level .
Measurements in the next year on Subaru will increase their z = 6.6 LAE sample by a factor of five and tighten these limits .
If the clustering signature of reionization is detected in a LAE survey , a comparison with a Lyman-break or a H \alpha survey in the same field would confirm the reionization hypothesis .
We discuss the optimal LAE survey specifications for detecting reionization , with reference to upcoming programs .