A magnetic tomography of a cavity state

A method to determine the state of a single quantized cavity mode is proposed. By adiabatic passage, the quantum state of the field is transfered completely onto an internal Zeeman sub-manifold of an atom. Utilizing a method of Newton and Young, we can determine this angular momentum state uniquely, by a finite number of magnetic dipole measurements with Stern-Gerlach analyzers. An example illustrates the influence of dissipation.