Before revision:  We also obtain an adversarially robust algorithm for the L_2-heavy hitters problem using \frac{\log n{\epsilon^2}} bits of space. Our bounds are optimal up to \text{poly(\log\log n+\log(1/\epsilon)) factors, and improve the 1{\epsilon^3} dependence of }  Ben-Eliezer et  al.
After revision:  We also obtain an adversarially robust algorithm for the L_2-heavy hitters problem using \frac{\log n{\epsilon^2}} (\log\log n+\log(1/\epsilon)) factors, and improve the 1{\epsilon^3} dependence of } Ben-Eliezer et al.