Non-Pauli Observables for CWS Codes
  It is known that nonadditive quantum codes are more optimal for error correction when compared to stabilizer codes. The class of codeword stabilized codes (CWS) provides tools to obtain new nonadditive quantum codes by reducing the problem to finding nonlinear classical codes. In this work, we establish some results on the kind of non-Pauli operators that can be used as decoding observables for CWS codes and describe a procedure to obtain these observables. 
Douglas F. G. Santiago, Renato Portugal, Nolmar Melo
quant-ph cs.IT math.IT