ABSTRACT
Quantum state tomography via local measurements is an efficient tool for characterizing quantum states. However, it requires that the original global state be uniquely determined (UD) by its local reduced density matrices (RDMs). In this work, we demonstrate for the first time a class of states that are UD by their RDMs under the assumption that the global state is pure, but fail to be UD in the absence of that assumption. This discovery allows us to classify quantum states according to their UD properties, with the requirement that each class be treated distinctly in the practice of simplifying quantum state tomography. Additionally, we experimentally test the feasibility and stability of performing quantum state tomography via the measurement of local RDMs for each class. These theoretical and experimental results demonstrate the advantages and possible pitfalls of quantum state tomography with local measurements.
BIOGRAPHY
Bei Zeng received the B.Sc. degree in physics and mathematics and M.Sc. degree in physics from Tsinghua University, Beijing, China, in 2002 and 2004, respectively. She received the Ph.D. degree in physics from Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts, USA, in 2009. From 2009 to 2010, she was a postdoctoral fellow at the Institute for Quantum Computing (IQC) and the Department of Combinatorics & Optimization, University of Waterloo, Waterloo, Ontario, Canada. In 2010, she joined the Department of Mathematics & Statistics, University of Guelph, Guelph, Ontario, Canada, as an assistant professor, and promoted to Tenured Associate Professor in 2014 and Professor in 2018.