We improve performance of the asymptotically good quantum codes constructed by Ashikhmin, Litsyn, and Tsfasman (see Phys. Rev. A, vol.63, no.3, p.032311, Mar. 2001), by using more rational points on algebraic curves.
It is known that quantum error correction can be achieved using classical binary codes or additive codes over F/sub 4/. Asymptotically good quantum codes have been constructed from algebraic-geometry codes and a bound on (/spl delta/, R) was computed from the Tsfasman-Vladut-Zink bound of the theory of classical algebraic-geometry codes. In this correspondence, by the use of a concatenation technique we construct a family of asymptotically good quantum codes exceeding the bound in a small interval.