Please use this identifier to cite or link to this item: http://thuvien.ued.udn.vn/handle/TVDHSPDN_123456789/56306
Title: Quantum state smoothing: why the types of observed and unobserved measurements matter
Authors: Chantasri, Areeya
Guevara, Ivonne
Wiseman, Howard M.
Keywords: Quantum state estimation
Smoothing
Quantum trajectory
Correlation function
Issue Date: 22/8/2019
Publisher: IOP Publishing
Abstract: Weinvestigate the estimation technique called quantum state smoothing introduced in (Guevara and Wiseman 2015 Phys. Rev. Lett. 115 180407), which offers a valid quantum state estimate for a partially monitored system, conditioned on the observed record both prior and posterior to an estimation time. The technique was shown to give a better estimate of the underlying true quantum states than the usual quantum filtering approach. However, the improvement in estimation fidelity, originally examined for a resonantly driven qubit coupled to two vacuum baths, was also shown to vary depending on the types of detection used for the qubit’s fluorescence. In this work, we analyse this variation in a systematic way for the first time.Wefirst define smoothing power using an average purity recovery and a relative average purity recovery, of smoothing over filtering. Then, we explore the power for various combinations of fluorescence detection for both observed and unobserved channels.Wenext propose a method to explain the variation of the smoothing power, based on multitime correlation strength between fluorescence detection records. The method gives a prediction of smoothing power for different combinations, which is remarkably successful in comparison with numerically simulated qubit trajectories.
Description: New Journal of Physics 21 (2019)
URI: http://thuvien.ued.udn.vn/handle/TVDHSPDN_123456789/56306
Appears in Collections:Vật lý và ứng dụng (TC)

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