Direct measurement of the quantum state of the electromagnetic field in   a superconducting transmission line
  We propose an experimental procedure to directly measure the state of an electromagnetic field inside a resonator, corresponding to a superconducting transmission line, coupled to a Cooper-pair box (CPB). The measurement protocol is based on the use of a dispersive interaction between the field and the CPB, and the coupling to an external classical field that is tuned to resonance with either the field or the CPB. We present a numerical simulation that demonstrates the feasibility of this protocol, which is within reach of present technology. 
F. de Melo, L. Aolita, F. Toscano, L. Davidovich