Enlargement of Calderbank-Shor-Steane quantum codes

It is shown that a classical error correcting code C = [n, k, d] which cont ains its dual, CI C C, and which can be enlarged to C' = [n, k' > k + 1, d' ], can be converted into a quantum code of parameters [[In, k+k' - n, min(d , [3d'/2])]]. This is a generalization of a previous construction, it enabl es many new codes of good efficiency to be discovered. Examples based on cl assical Bose-Chaudhuri-Hocquenghem (ECR) codes are discussed.