Nonlocality, Asymmetry, and Distinguishing Bipartite States
Abstract
Entanglement is an useful resource because some global operations cannot be locally implemented using classical communication. We prove a number of results about what is and is not locally possible. We focus on orthogonal states, which can always be globally distinguished. We establish the necessary and sufficient conditions for a general set of 2x2 quantum states to be locally distinguishable, and for a general set of 2xn quantum states to be distinguished given an initial measurement of the qubit. These results reveal a fundamental asymmetry to nonlocality, which is the origin of ``nonlocality without entanglement'', and we present a very simple proof of this phenomenon.
Cite
@article{arxiv.quant-ph/0202034,
title = {Nonlocality, Asymmetry, and Distinguishing Bipartite States},
author = {Jonathan Walgate and Lucien Hardy},
journal= {arXiv preprint arXiv:quant-ph/0202034},
year = {2009}
}
Comments
5 pages, 1 figure. Improved in line with referees comments, references added, typo corrected. To appear in Phys. Rev. Lett