Two-stage quantum nondemolition experiment
Richard E. Slusher, Arthur La Porta, S. T. Ho, Bernard Yurke · International Quantum Electronics Conference · 1990
We have previously demonstrated a backaction evading (BAE) measurement apparatus based on simple optics and a parametric downconversion amplifier.1 This apparatus avoids contamination of the measured signal by the measurement process. Quantum correlations were demonstrated between the measured portion of the signal and the transmitted signal, while the mean level of the transmitted signal is equal to that of the input.