Strong many-particle localization is studied in a 1D array of perpetually coupled qubits and an equivalent 1D system of interacting fermions. We construct a bounded sequence of the on-site fermion energies, or qubit transition frequencies, that suppresses resonant hopping between both nearest and remote neighbors. Besides quasi-exponential decay of the single-particle transition amplitude,it leads to long lived strongly localized many-particle states. This makes quantum computing with time-independent qubit coupling viable.
We analyze localization of interacting excitations in a system of qubits or spins. The system is modeled by a spin chain with an anisotropic (XXZ) exchange coupling in a magnetic field. Localization occurs on a defect with an excess on-site spin-flip energy. Such a defect corresponds to a qubit with the level spacing different from other qubits. Because of the interaction, a single defect may lead to multiple localized states. We find energy spectra and localization lengths of the two-excitation states. An excitation remains localized on the defect even where energy conservation allows scattering into extended states. This is due to destructive quantum interference in the two-excitation scattering channels, and it facilitates the operation of a quantum computer. Analytical results are obtained for strong anisotropy and are confirmed by numerical studies.