%0 Journal Article %T Bayesian feedback control of a two-atom spin-state in an atom-cavity system %A Stefan Brakhane %A Wolfgang Alt %A Tobias Kampschulte %A Miguel Martinez-Dorantes %A Ren¨¦ Reimann %A Seokchan Yoon %A Artur Widera %A Dieter Meschede %J Physics %D 2012 %I arXiv %R 10.1103/PhysRevLett.109.173601 %X We experimentally demonstrate real-time feedback control of the joint spin-state of two neutral Caesium atoms inside a high finesse optical cavity. The quantum states are discriminated by their different cavity transmission levels. A Bayesian update formalism is used to estimate state occupation probabilities as well as transition rates. We stabilize the balanced two-atom mixed state, which is deterministically inaccessible, via feedback control and find very good agreement with Monte-Carlo simulations. On average, the feedback loops achieves near optimal conditions by steering the system to the target state marginally exceeding the time to retrieve information about its state. %U http://arxiv.org/abs/1206.3184v1