Enlargement of Calderbank-Shor-Steane quantum codes

It is shown that a classical error correcting code C=[n,k,d] which contains its dual, C/sup /spl perp///spl sube/C, and which can be enlarged to C'=[n,k'>k+1,d'], can be converted into a quantum code of parameters [[n,k+k'-n,min(d,[3d'/2])]]. This is a generalization of a previous construction, it enables many new codes of good efficiency to be discovered. Examples based on classical Bose-Chaudhuri-Hocquenghem (BCH) codes are discussed.