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BY-NC-ND 4.0 license Open Access Published by De Gruyter Open Access September 23, 2017

Hamiltonian extensions in quantum metrology

  • Julien Mathieu Elias Fraïsse EMAIL logo and Daniel Braun


We study very generally towhat extent the uncertainty with which a phase shift can be estimated in quantum metrology can be reduced by extending the Hamiltonian that generates the phase shift to an ancilla system with a Hilbert space of arbitrary dimension, and allowing arbitrary interactions between the original system and the ancilla. Such Hamiltonian extensions provide a general framework for open quantum systems, as well as for “non-linear metrology schemes” that have been investigated over the last few years. We prove that such Hamiltonian extensions cannot improve the sensitivity of the phase shift measurement when considering the quantum Fisher information optimized over input states.


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Received: 2016-12-2
Accepted: 2017-8-7
Published Online: 2017-9-23
Published in Print: 2017-9-26

© 2017

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

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