Nonunity gain quantum nondemolition measurements based on measurement and repreparation
Jessica Schneider, O. Glöckl, Gerd Leuchs, Ulrik L. Andersen · Optics Letters · 2006
We demonstrate experimentally a nonunity gain quantum nondemolition measurement based on a simple homodyne measurement and recreation strategy. Although the output state is an amplified version of the input state, the device meets standard criteria for QND measurements: the transfer coefficient was measured to 1.78, and the conditional variance was measured to 0.66.