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Quantum Probes for Ohmic Environments at Thermal Equilibrium

1
Faculty of Physics, Shahid Bahonar University of Kerman, Kerman 76169-14111, Iran
2
Quantum Technology Lab, Dipartimento di Fisica “Aldo Pontremoli”, Università di Milano, I-20133 Milano, Italy
*
Author to whom correspondence should be addressed.
Entropy 2019, 21(5), 486; https://doi.org/10.3390/e21050486
Received: 16 April 2019 / Revised: 7 May 2019 / Accepted: 8 May 2019 / Published: 12 May 2019
(This article belongs to the Special Issue Open Quantum Systems (OQS) for Quantum Technologies)
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Abstract

It is often the case that the environment of a quantum system may be described as a bath of oscillators with an ohmic density of states. In turn, the precise characterization of these classes of environments is a crucial tool to engineer decoherence or to tailor quantum information protocols. Recently, the use of quantum probes in characterizing ohmic environments at zero-temperature has been discussed, showing that a single qubit provides precise estimation of the cutoff frequency. On the other hand, thermal noise often spoil quantum probing schemes, and for this reason we here extend the analysis to a complex system at thermal equilibrium. In particular, we discuss the interplay between thermal fluctuations and time evolution in determining the precision attainable by quantum probes. Our results show that the presence of thermal fluctuations degrades the precision for low values of the cutoff frequency, i.e., values of the order ω c T (in natural units). For larger values of ω c , decoherence is mostly due to the structure of environment, rather than thermal fluctuations, such that quantum probing by a single qubit is still an effective estimation procedure. View Full-Text
Keywords: open quantum systems; quantum probes; ohmic environments open quantum systems; quantum probes; ohmic environments
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Salari Sehdaran, F.; Bina, M.; Benedetti, C.; Paris, M.G.A. Quantum Probes for Ohmic Environments at Thermal Equilibrium. Entropy 2019, 21, 486.

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