Quantum change point
Abstract
Sudden changes are ubiquitous in nature. Identifying them is of crucial importance for a number of applications in medicine, biology, geophysics, and social sciences. Here we investigate the problem in the quantum domain, considering a source that emits particles in a default state, until a point where it switches to another state. Given a sequence of particles emitted by the source, the problem is to find out where the change occurred. For large sequences, we obtain an analytical expression for the maximum probability of correctly identifying the change point when joint measurements on the whole sequence are allowed. We also construct strategies that measure the particles individually and provide an online answer as soon as a new particle is emitted by the source. We show that these strategies substantially underperform the optimal strategy, indicating that quantum sudden changes, although happening locally, are better detected globally.
Cite
@article{arxiv.1605.01916,
title = {Quantum change point},
author = {Gael Sentís and Emilio Bagan and John Calsamiglia and Giulio Chiribella and Ramon Munoz-Tapia},
journal= {arXiv preprint arXiv:1605.01916},
year = {2016}
}
Comments
4+8 pages, published version. New results added, including a theorem applicable to general multihypothesis discrimination problems