Quantum-limited estimation of coherence under thermal noise in photon-starved states
ORAL
Abstract
To most efficiently estimate a parameter of a quantum system, one needs to choose the optimal measurement that creates the conditions for the most efficient estimator to act. Specifically, one needs to implement the measurement that achieves the quantum Fisher information (qFi) for that particular estimation task. In this work, we search for an optimal measurement for estimating the coherence, parameterised as $\eta $, of a mixed state composed of coherent light and thermal (incoherent) light. Our search is limited to photon-starved signals, with signal strength of n\textunderscore bar\textless \textless 1. We found that the classical choice of measurement, direct detection was suboptimal, whereas homodyne detection approached the qFi for estimating coherence for the low coherence $\mbox{(}\eta \mbox{\sim 0)}$ range.
*Research was sponsored by the ARO and was accomplished under Grant Number: W911NF-20-1-0235. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of ARO or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein.
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