“…However, noise and imperfections still stand in our way. While the active strategies to prevent errors, such as quantum error correcting codes [17,18,19,20] may, in principle, be universal as claimed, passive prevention methods have hardware resource advantages. For example, decoherence-free subspaces (DFS) and noiseless subsystems (NS) [21,22,23,24] are based on the symmetry of the system-bath interaction, so do not require active detection and correction of errors.…”