the repetitive N-qubit codes cannot be used for quantum error correction, but can be used for quantum error detection. In the latter case it is sufficient to use only two qubits for the encoding. In the analysis we demonstrate a useful technique of unraveling the qubit energy relaxation into „relaxation“ and „no relaxation“ scenarios. Also, we propose and numerically analyze several two-qubit algorithms for quantum error detection/correction, which can be readily realized at the present-day level of the phase qubit technology.