A comparison of decoherence-free subsystem/subspace for partially broken symmetry
S. Siddiqui, Julio R. Gea-Banacloche · Quantum Information and Computation · 2005
We study the performance of the 3-qubit decoherence-free subsystem and the 4-qubit decoherence-free subspace in the presence of partially correlated noise. We characterize their performance in terms of the average and worst-case fidelity, as a function of the ratio of the interqubit distance to the correlation length of the noise, and find that, in general, more symmetric arrangements (triangles or squares) lead to better performance. Overall, we find the 3-qubit code to perform better than the 4-qubit code by about a factor of 2 in the average infidelity. We observe that this is related to the greater robustness of this code against uncorrelated (independent) errors.