Dynamical phase transitions as a resource for quantum enhanced metrology

Macieszczak, Katarzyna and Guţă, Mădălin and Lesanovsky, Igor and Garrahan, Juan P. (2016) Dynamical phase transitions as a resource for quantum enhanced metrology. Physical Review A, 93 (2). 022103/1-022103/10. ISSN 2469-9926

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We consider the general problem of estimating an unknown control parameter of an open quantum system. We establish a direct relation between the evolution of both system and environment and the precision with which the parameter can be estimated. We show that when the open quantum system undergoes a first-order dynamical phase transition the quantum Fisher information (QFI), which gives the upper bound on the achievable precision of any measurement of the system and environment, becomes quadratic in observation time (cf. “Heisenberg scaling”). In fact, the QFI is identical to the variance of the dynamical observable that characterizes the phases that coexist at the transition, and enhanced scaling is a consequence of the divergence of the variance of this observable at the transition point. This identification makes it possible to establish the finite time scaling of the QFI. Near the transition the QFI is quadratic in time for times shorter than the correlation time of the dynamics. In the regime of enhanced scaling the optimal measurement whose precision is given by the QFI involves measuring both system and output. As a particular realization of these ideas, we describe a theoretical scheme for quantum enhanced estimation of an optical phase shift using the photons being emitted from a quantum system near the coexistence of dynamical phases with distinct photon emission rates.

Item Type: Article
Schools/Departments: University of Nottingham, UK > Faculty of Science > School of Mathematical Sciences
University of Nottingham, UK > Faculty of Science > School of Physics and Astronomy
Identification Number: https://doi.org/10.1103/PhysRevA.93.022103
Depositing User: Jacob, Mr Tim
Date Deposited: 03 Jan 2017 09:20
Last Modified: 03 Jan 2017 09:23
URI: http://eprints.nottingham.ac.uk/id/eprint/39539

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