Robust solid-state qubits based on nuclear quadrupole resonance technique

Advances in quantum information processing can open a way for their numerous applications in various fields of science and technology: communication, precision measurement, computing, nano-scale detectors, and sensors. Solid state with nucleus spins-1/2 is one of the natural bases for creation of a system of the interacting qubits. It was theoretically predicted and experimentally confirmed that logical gates can be realized using quantum states of a single nucleus with a spin I > 1/2. In the present paper we consider representation of a quadrupole spin-3/2 and 7/2 as well as a diatomic molecule as systems of interacting fictitious spins-1/2. It is shown that the Hamiltonians of these systems contain terms describing multi-body interactions and constants of these interactions depend on the applied magnetic field. Considering the fictitious spins as qubits influence of the unique properties of the systems on concurrence is analyzed. The representation of the molecule as a fictitious spin-1/2 system allows us to consider the bipartite concurrences between qubits formatted by the molecule states. The dependence of the concurrences on the magnetic field and its frequency can be used at development of methods to control qubit states and to realize computing protocols. Representation of spins I > 1/2 and their systems as systems of interacting fictitious spins-1/2 can be used at the investigation of properties of complex systems and realization of quantum computation.