Abstract
We investigate the extent to which “interaction-free” measurements perturb the state of quantum systems. We show that the absence of energy exchange during the measurement is not a sufficient criterion to preserve that state, as the quantum system is subject to measurement-dependent decoherence. While it is possible in general to design interaction-free measurement schemes that do preserve that state, the requirement of quantum coherence preservation rapidly leads to a very low efficiency. Our results, which have a simple interpretation in terms of “which-way” arguments, open up the way to novel quantum nondemolition techniques.
- Received 5 July 2000
DOI:https://doi.org/10.1103/PhysRevA.62.060101
©2000 American Physical Society