Driving atoms into decoherence-free states

Summary form only given. Quantum computing has attracted much interest since it became clear that quantum computers are in principle able to solve hard computational problems more efficiently than present classical computers. The main obstacle inhibiting realizations is decoherence and for this reason error correction schemes have been invented. Recently it has become clear that there may exist states in the Hilbert space that are in principle free from decoherence. These states arise if the coupling to the environment possesses a certain symmetry and form a decoherence-free subspace (DFS). If one uses only these states as the qubits for quantum computing the dependence on error correction codes may be much reduced. In this paper we propose an example of a DFS and show that the interaction with the environment may actually be exploited to confine the system to a DFS when operations are performed.