Quantum-Non-Demolition Endoscopic Tomography
  We present a new indirect method to measure the quantum state of a single mode of the electromagnetic field in a cavity. Our proposal combines the idea of (endoscopic) probing and that of tomography in the sense that the signal field is coupled via a quantum-non-demolition Hamiltonian to a meter field on which then quantum state tomography is performed using balanced homodyne detection. This technique provides full information about the signal state. We also discuss the influence of the measurement of the meter on the signal field. 
Mauro Fortunato (1 and 2), Paolo Tombesi (1), and Wolfgang P. Schleich   (2) ((1) University of Camerino, (2) University of Ulm)