| Abstract: | The existence of decoherence-free subspace (DFS) has been discussedwidely. In this paper, we propose an alternative scheme forgenerating the four-atom $W$ states by manipulating DF qubits. Theatoms are divided into two pairs and trapped in two separate opticalcavities. Manipulation of atoms within DFS may generate a two-atommaximally entangled state in an individual cavity, which is a stablestate. After driving the system out of DFS, the atoms will interactresonantly with the cavity field. The photons leaking from thecavities interfere at the beamsplitter, which destroys which-pathinformation, and are finally detected by one of the detectors,leading to the generation of a $W$ state. In addition, the numericalsimulation indicates that the fidelity of the prepared state can, fora very wide parameter regime, be very close to unity. |
