The appearance of decoherence-recoherence events is analyzed in a dephasing model of a qubit which interacts with a bosonic environment. The initial condition is prepared from the thermal state of the whole system by performing a nonselective measurement on the qubit. Decoherence-recoherence events appear in the reduced dynamics of the qubit uniquely if special nonselective preparation measurements are adopted and the spectral density of the system fulfills determined conditions. General lower bounds are found for the number of decoherence-recoherence events in terms of the properties of the measurement scheme and of the spectral density. The number is finite for canonical spectral densities which are super-ohmic, perturbed super-ohmic, or ohmic at low frequencies and are arbitrarily tailored at high frequencies. The number is infinite in the sub-ohmic regime and for perturbations of the sub-ohmic or ohmic regime. Decoherence-recoherence times are evaluated, analytically and numerically, for ohmic-like spectral densities with exponential high-frequency cutoffs.

中文翻译：

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使用特殊的非选择性测量方案准备量子位的退相干-再相干时间

在与玻色子环境相互作用的量子位相移模型中分析退相干-再相干事件的出现。通过对量子比特执行非选择性测量，从整个系统的热状态准备初始条件。如果采用特殊的非选择性制备测量并且系统的光谱密度满足确定的条件，则退相干 - 再相干事件唯一地出现在量子比特的减少动力学中。根据测量方案和光谱密度的特性，找到退相干-再相干事件数量的一般下限。对于在低频下为超欧姆、扰动超欧姆或欧姆并且在高频下任意定制的规范谱密度，该数字是有限的。在亚欧姆范围内以及对于亚欧姆或欧姆范围的扰动，该数量是无限的。对于具有指数高频截止的类似欧姆的光谱密度，对退相干-再相干时间进行了分析和数值评估。