Information extraction: one spin versus two spins

演讲人: Prof. Shunlong Luo Chinese Academy of Mathematics and Systems Science, Chinese Academy of Sciences
时间: 2014-10-10 11:00-2014-10-10 12:00
地点:FIT 1-222

We consider extracting information from one spin, as well as from two parallel or antiparallel spins, from the viewpoint of parameter estimation. By comparing two fundamental figures of merit based on fidelity and quantum Fisher information for assessing information quality, we demonstrate that these criteria yield different strategies for optimally extracting spin information. A surprising observation is that while for a single spin as well as for parallel spins, quantum Fisher information cannot be fully extracted by any uniform measurement, this is not the case for antiparallel spins. A simple uniform measurement fully extracting quantum Fisher information in antiparallel spins is identified. This reveals a significant feature of antiparallel spins from the perspective of Fisher information, and provides an alternative illustration of the idea that antiparallel spins carry more information than parallel spins.