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^⊥⊆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