Ancilla-Assisted Enhancement of Channel Estimation for Low-Noise Parameters

In order to make a unified treatment for estimation problems of a very small noise or a very weak signal in a quantum process, we introduce the notion of a low-noise quantum channel with one noise parameter. It is known in several examples that prior entanglement together with nonlocal output measur...

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Bibliographic Details
Published in:arXiv.org 2005-08
Main Authors: Hotta, Masahiro, Karasawa, Tokishiro, Ozawa, Masanao
Format: Article
Language:English
Subjects:
Entanglement
Noise
Order parameters
Parameter estimation
Performance enhancement
Signal processing
Online Access:Get full text
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Summary:In order to make a unified treatment for estimation problems of a very small noise or a very weak signal in a quantum process, we introduce the notion of a low-noise quantum channel with one noise parameter. It is known in several examples that prior entanglement together with nonlocal output measurement improves the performance of the channel estimation. In this paper, we study this ``ancilla-assisted enhancement'' for estimation of the noise parameter in a general low-noise channel. For channels on two level systems we prove that the enhancement factor, the ratio of the Fisher information of the ancilla-assisted estimation to that of the original one, is always upper bounded by 3/2. Some conditions for the attainability are also given with illustrative examples.
ISSN:2331-8422
DOI:10.48550/arxiv.0507055