## RALPH » Reliably Distinguishing States in Qutrit Channels Using One-way LOCC

Sponsor: Prof. Javed Aslam

Downloads: Slides

Presentation date: Nov. 17th, 2005

## Proposal

Daniel Matysiak and Christopher King have analyzed how nonlocality appears in a general class of quantum problems, namely, by looking at entangled subspaces of tensor product spaces, and asking: how entangled are the states in the subspace, or, more specifically, is it possible to disentangle a basis of states by using local measurements on each of the sub-systems to determine the basis states? It turns out that this is always possible when the subspace is 3-dimensionsal. The result is quite mysterious, as there is currently no known mathematical or physical reason to expect that this should be possible. There are several implications. First, one would be able to remove all "noise" from a qutrit quantum channel by making coordinated measurements on the system and the environment. Second, it would follow that product states are just as "good" as entangled states in this bipartite system, i.e. since LOCC is much easier to perform than entangled measurements, one would be able to simulate entangled measurements using LOCC.

I plan on presenting the results of our work and what they mean as well as the consequences of this conjecture. This includes a description of the tertiary systems we are using (namely qutrits) and environment-assisted measurements.

The work described here is explained in more detail in the respective article (a preprint is available at http://arxiv.org/abs/quant-ph/0510004; it has been submitted to
*Quantum Information and Computation*, a journal published by Rinton Press).