Protected Rabi oscillation induced by natural interactions among physical qubits

For a system composed of nine qubits, we show that natural interactions among the qubits induce the time evolution that can be regarded, at discrete times, as the Rabi oscillation of a logical qubit. Neither fine tuning of the parameters nor switching of the interactions is necessary. Although straightforward application of quantum error correction fails, we propose a protocol by which the logical Rabi oscillation is protected against all single-qubit errors. The present method thus opens a simple and realistic way of protecting the unitary time evolution against noise.Comment: In this revised manuscript, new sections V, VI, VII and new appendices A, B, C have been added to give detailed discussions. 13 pages, 4 figure