Fig. 1. (a) Generation of atomic entanglement in separated cavities coupled by a short optical fiber. Two-atom entanglement can be realized in a heralded way by detecting the transmission spectrum; (b) concrete atomic level structure and relevant transition.

Fig. 2. Transmission spectrum T as a function of the scanning frequency δ=ω−ωa. Spectral line A corresponds to the state |ψ〉A=|s1,s2〉, spectral line B corresponds to the state |ψ〉B=1/2(|g1,s2〉+|s1,g2〉), spectral line C corresponds to the state |ψ〉C=|g1,g2〉, and δω is the minimal shift of three spectral lines. Parameters are κ=γ, g=4κ^[36], J=100  g^[8], and Δ=15  g.

Fig. 3. Probability P of the atomic qubit loss as a function of the time t. Parameters are (g,κ,γ)/(2π)=(16,4.2,2.6)  MHz^[36], Ω/2π=4  MHz, J=100  g^[8], and Δ=15  g.