Testing sequential quantum measurements: how can maximal knowledge be   extracted?
  The extraction of information from a quantum system unavoidably implies a modification of the measured system itself. It has been demonstrated recently that partial measurements can be carried out in order to extract only a portion of the information encoded in a quantum system, at the cost of inducing a limited amount of disturbance. Here we analyze experimentally the dynamics of sequential partial measurements carried out on a quantum system, focusing on the trade-off between the maximal information extractable and the disturbance. In particular we consider two different regimes of measurement, demonstrating that, by exploiting an adaptive strategy, an optimal trade-off between the two quantities can be found, as observed in a single measurement process. Such experimental result, achieved for two sequential measurements, can be extended to N measurement processes. 
Eleonora Nagali, Simone Felicetti, Pierre-Louis de Assis, Vincenzo   D'Ambrosio, Radim Filip, and Fabio Sciarrino
quant-ph