论文标题
热环境中损耗参数的高斯量子估计
Gaussian quantum estimation of the lossy parameter in a thermal environment
论文作者
论文摘要
有损耗的骨通道在许多量子信息任务中起着重要作用，因为它们在实验中近似于热耗散。在这里，我们将它们的计量能力表征为无怠速和纠缠辅助案例，分别使用单模和两模式的高斯状态为探针。在估计有损耗参数的问题中，我们研究了通用温度和损耗参数制度的能量受限的量子渔民信息（QFI），显示了最佳探针的定性行为。我们半分析表明，两种模式挤压效果状态为损失参数和温度的任何值都优化了QFI。我们讨论了{\ it Total} QFI的优化，其中允许探针的数量通过保持总能量约束来变化。在这种情况下，我们阐明了“影子效应”在获得量子优势方面的作用。我们还考虑了环境的光子数归一化，广泛用于量子照明和量子读取方案的分析。通过这种归一化，我们证明了大带宽TMSV状态是任何参数值的最佳探针。在这里，量子优势最多是$ 2 $，并且在{\ it any}损耗参数值的明亮环境案例中达到。最后，我们讨论了结果对量子照明和量子阅读应用的含义。
Lossy bosonic channels play an important role in a number of quantum information tasks, since they well approximate thermal dissipation in an experiment. Here, we characterize their metrological power in the idler-free and entanglement-assisted cases, using respectively single- and two-mode Gaussian states as probes. In the problem of estimating the lossy parameter, we study the energy-constrained quantum Fisher information (QFI) for generic temperature and lossy parameter regimes, showing qualitative behaviours of the optimal probes. We show semi-analytically that the two-mode squeezed-vacuum state optimizes the QFI for any value of the lossy parameter and temperature. We discuss the optimization of the {\it total} QFI, where the number of probes is allowed to vary by keeping the total energy-constrained. In this context, we elucidate the role of the "shadow-effect" for reaching a quantum advantage. We also consider a photon-number normalization for the environment, widely used in the analysis of quantum illumination and quantum reading protocols. With this normalization, we prove that the large bandwidth TMSV state is the optimal probe for any parameter value. Here, the quantum advantage is of at most a factor of $2$, and is reached in the bright environment case for {\it any} lossy parameter values. Finally, we discuss the implications of our results for quantum illumination and quantum reading applications.
