  In Fourier restriction problems, a cone and a paraboloid are model surfaces.
The sharp bilinear cone restriction estimate was first shown by Wolff, and
later the endpoint was obtained by Tao. For a paraboloid, the sharp $L^2$
bilinear restriction estimate was obtained by Tao, but the endpoint was
remained open. In this paper we prove the endpoint $L^2$ bilinear restriction
estimate for a paraboloid.
