Entangling measurements for multiparameter estimation with two qubits
Abstract
Careful tailoring the quantum state of probes offers the capability of investigating matter at unprecedented precisions. Rarely, however, the interaction with the sample is fully encompassed by a single parameter, and the information contained in the probe needs to be partitioned on multiple parameters. There exist then practical bounds on the ultimate joint-estimation precision set by the unavailability of a single optimal measurement for all parameters. Here we discuss how these considerations are modified for two-level quantum probes - qubits - by the use of two copies and entangling measurements. We find that the joint estimation of phase and phase diffusion benefits from such collective measurement, while for multiple phases, no enhancement can be observed. We demonstrate this in a proof-of-principle photonics setup.
Cite
@article{arxiv.1704.03327,
title = {Entangling measurements for multiparameter estimation with two qubits},
author = {Emanuele Roccia and Ilaria Gianani and Luca Mancino and Marco Sbroscia and Fabrizia Somma and Marco G. Genoni and Marco Barbieri},
journal= {arXiv preprint arXiv:1704.03327},
year = {2017}
}