Abstract

The act of measurement of a quantum mechanical variable introduces uncertainty in subsequent measurements made on the same system but not necessarily for the same variable. Back-action-evading or quantum nondemolition measurement schemes perturb variables conjugate to the one being measured, which itself remains unchanged by the measurement process. Thus repeated measurements of the quantum nondemolition detection (QND) variable can determine its evolution without disturbing it.

© 1987 Optical Society of America