Variational-State Quantum Metrology
Abstract
Quantum technologies exploit entanglement to enhance various tasks beyond their classical limits including computation, communication and measurements. Quantum metrology aims to increase the precision of a measured quantity that is estimated in the presence of statistical errors using entangled quantum states. We present a novel approach for finding (near) optimal states for metrology in the presence of noise, using variational techniques as a tool for efficiently searching the classically intractable high-dimensional space of quantum states. We comprehensively explore systems consisting of up to 9 qubits and find new highly entangled states that are not symmetric under permutations and non-trivially outperform previously known states up to a constant factor 2. We consider a range of environmental noise models; while passive quantum states cannot achieve a fundamentally superior scaling (as established by prior asymptotic results) we do observe a significant absolute quantum advantage. We finally outline a possible experimental setup for variational quantum metrology which can be implemented in near-term hardware.
Cite
@article{arxiv.1908.08904,
title = {Variational-State Quantum Metrology},
author = {Bálint Koczor and Suguru Endo and Tyson Jones and Yuichiro Matsuzaki and Simon C. Benjamin},
journal= {arXiv preprint arXiv:1908.08904},
year = {2020}
}
Comments
31 pages, 10 figures -- added more discussion about, e.g., the optimisation and the ansatz structure