Decoherence-free quantum-information processing using dipole-coupled qubits

We propose a quantum-information processor that consists of decoherence-freelogical qubits encoded into arrays of dipole-coupled qubits. High-fidelitysingle-qubit operations are performed deterministically within adecoherence-free subsystem without leakage via global addressing of bichromaticlaser fields. Two-qubit operations are realized locally with four physicalqubits, and between separated logical qubits using linear optics. We show howto prepare cluster states using this method. We include allnon-nearest-neighbor effects in our calculations, and we assume the qubits arenot located in the Dicke limit. Although our proposal is general to any systemof dipole-coupled qubits, throughout the paper we use nitrogen-vacancy (NV)centers in diamond as an experimental context for our theoretical results.Comment: 7 pages, 5 figure