Classical Robustness of Quantum Unravellings

Abstract

We introduce three measures which quantify the degree to which quantum systems possess the robustness exhibited by classical systems when subjected to continuous observation. Using these we show that for a fixed environmental interaction the level of robustness depends on the measurement strategy, or unravelling, and that no single strategy is maximally robust in all ways.

8 Pages, 2 figures, Version 2. Minor changes to wording for clarification and some references added. Accepted for publication in Europhysics Letters