Survey parameters for detecting 21-cm-Ly alpha emitter cross-correlations with the Square Kilometre Array

Detections of the cross-correlation signal between the 21 cm signal during reionization and high-redshift Lyman-alpha (Ly alpha) emitters (LAEs) are subject to observational uncertainties which mainly include systematics associated with radio interferometers and LAE selection. These uncertainties can be reduced by increasing the survey volume and/or the survey luminosity limit, i.e. the faintest detectable Ly a luminosity. We use our model of high-redshift LAEs and the underlying reionization state to compute the uncertainties of the 21-cm-LAE cross-correlation function at z similar or equal to 6.6 for observations with SKA1-Low and LAE surveys with Delta z = 0.1 for three different values of the average inter-galactic medium (IGM) ionization state ( similar or equal to 0.1, 0.25, 0.5). At z similar or equal to 6.6, we find SILVERRUSH type surveys, with a field of view of 21 deg(2) and survey luminosity limits of L-alpha = 7.9 x 10(42) erg s(-1), to be optimal to distinguish between an IGM that is 50, 25, and 10 per cent neutral, while surveys with smaller fields of view and lower survey luminosity limits, such as the 5 and 10 deg(2) surveys with WFIRST, can only discriminate between a 50 and 10 per cent neutral IGM.