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arXiv:1905.06608 · Chinese Physics B

Modulating quantum Fisher information of qubit in dissipative cavity by coupling strength

Danping Lin, Yu Liu, Hong-Mei Zou

Published Nov 1, 2018• 5 citations
arXivHTMLPDF

Abstract

By using the non-Markovian master equation, we investigate the effect of the cavity and the environment on the quantum Fisher information (QFI) of an atom qubit system in a dissipation cavity. We obtain the formulae of QFI for two different initial states and analyze the effect of the atom–cavity coupling and the cavity–reservoir coupling on the QFI. The results show that the dynamic behavior of the QFI is obviously dependent on the initial atomic states, the atom–cavity coupling, and the cavity–reservoir coupling. The stronger the atom–cavity coupling, the quicker the QFI oscillates, and the slower the QFI decreases. In particular, the QFI will tend to be a stable value rather than zero if the atom–cavity coupling is large enough. On the other hand, the smaller the cavity–reservoir coupling, the stronger the non-Markovian effect, and the slower the QFI decays. In other words, choosing the best parameter can improve the accuracy of the parameter estimation. In addition, the physical explanation of the dynamic behavior of the QFI is given by means of the QFI flow.

DOI
10.1088/1674-1056/27/11/110303

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Abstract In this work, we investigate quantum Fisher information (QFI) and quantum coherence (QC) of an atom in a dissipative cavity. In a zero-temperature reservoir and with one excitation number, we obtain the analytical solutions of QFI and QC as well as their relationship for Ohmic and Lorentzian reservoirs, respectively. The results show that both the atom–cavity coupling and the cavity–reservoir coupling can effectively protect QFI and QC. In particular, QFI and QC will tend to their stable values when the atom–cavity coupling or cavity–reservoir coupling is larger than a certain value. QC can augment QFI and can effectively improve the quantum metrology. In addition, we give a physical explanation of the dynamic behavior of QFI and QC using the decoherence rate.
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Abstract We study the quantum Fisher information (QFI) dynamics of the phase parameter in the enlarged cavity-reservoir systems at zero temperature under two situations of large N limit and non-Markovian environment, respectively. We find an important relation that the total quantities of QFI of the cavity and reservoir are equal to unit during the dynamical evolution. The lost QFI of the cavity transfers to its corresponding reservoir with the same quantities simultaneously. Moreover, we also find that the detuning parameter and non-Markovian effect are two significant factors to affect the preservation of QFI.
We consider the optimal parameter estimation for a two-level system coupled to multiple bosonic reservoirs. By using quantum Fisher information (QFI), we investigate the effect of the Markovian reservoirs’ number N on QFI in both weak and strong coupling regimes for a two-level system surrounded by N zero-temperature reservoirs of field modes initially in the vacua. The results show that the dynamics of QFI non-monotonically decays to zero with revival oscillations at some time in the weak coupling regime depending on the reservoirs’ parameters. Furthermore, we also present the relations between the QFI flow, the flows of energy and information, and the sign of the decay rate to gain insight into the physical processes characterizing the dynamics.
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We study the non-Markovian effect on the dynamics of the quantum Fisher information (QFI) by exactly solving a model consisting of a qubit system subjects to a zero-temperature reservoir for two different non-Markovian conditions: a high-QQQ cavity slightly off-resonant with the qubit transition frequency and a nonperfect photonic band gap, respectively. The phenomenon that the QFI, namely, the precision of estimation, changes dramatically with the environment structure and is affected by the environment memory effects. We find that revivals and retardation of QFI loss may occur by adjusting the cavity-qubit detuning, in the first case, while partial QFI trapping occurs in nonideal photonic band gaps and the decreasing gap width seriously destroys coherence, thus reducing the precision of estimation. These features make the qubit system in non-Markovian environments a good candidate for implementation of quantum optics schemes and information with high precision.