Ancilla-induced amplification of quantum Fisher information

. Given a quantum state with an unknown parameter being measured with a suitable observable, Quantum Fisher Information (QFI) is the amount of information that one can extract about the unknown parameter. QFI also quantifies the maximum achievable precision in estimating the unknown parameter with a...

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Bibliographic Details
Published in:European physical journal plus 2018-11, Vol.133 (11), p.460, Article 460
Main Authors: Sudheer Kumar, C. S., Mahesh, T. S.
Format: Article
Language:English
Subjects:
Amplification
Applied and Technical Physics
Atomic
Complex Systems
Condensed Matter Physics
Cramer-Rao bounds
Fisher information
High temperature
Mathematical and Computational Physics
Molecular
NMR
Nuclear magnetic resonance
Nuclear spin
Optical and Plasma Physics
Parameters
Physics
Physics and Astronomy
Quadratures
Qubits (quantum computing)
Regular Article
Science education
Theoretical
Tomography
Topology
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Description
Summary:. Given a quantum state with an unknown parameter being measured with a suitable observable, Quantum Fisher Information (QFI) is the amount of information that one can extract about the unknown parameter. QFI also quantifies the maximum achievable precision in estimating the unknown parameter with a given amount of resource via quantum Cramer-Rao bound. In this work, we describe a protocol to amplify QFI of a single target qubit precorrelated with a set of ancillary qubits. Using an NMR system as an example, we show that a single quadrature NMR signal of only ancillary qubits suffices to perform the quantum state tomography (QST) of target qubit’s deviation part of the density matrix. We experimentally demonstrate this protocol using a star-topology spin-system consisting of a 13 C nuclear spin as the target qubit and three 1 H nuclear spins as ancillary qubits. We prepare the target qubit in various initial states, perform experimental QST, and estimate the amplification of QFI in each case. We also show that, in a high-temperature scenario like in the case of NMR, the QFI amplification scales linearly with the number of ancillary qubits and quadratically with the Bloch radius.
ISSN:2190-5444
2190-5444
DOI:10.1140/epjp/i2018-12260-2