Multiatomic entanglement in a decoherence free subspace

Subradiant states - as a special kind of entangled states of several two-le vel atoms - have recently gained wide attention because these states are ex ceptional in the sense that they dissipate energy much slower then other co llective states. This property implies also that their decoherence is slow, and henceforth they are promising candidates for registers of a quantum co mputer. Here we propose a scheme which can be used to prepare subradiant st ates in a cavity. We present perturbative and also exact results showing th at after a certain time the evolution of a multiatomic system in a detuned cavity leads to an appropriate entangled state. At this time instant it is sufficient to apply subsequent laser pulses on a control atom in order prep are a state in the subradiant, i.e., a decoherence free subspace.