论文标题
表征三模式自发参数下转换过程的多部分非高斯纠缠过程
Characterizing Multipartite Non-Gaussian Entanglement for Three-Mode Spontaneous Parametric Down-Conversion Process
论文作者
论文摘要
最近，通过超导腔中的直接三模式自发参数下调观察到了强烈的非高斯状态[Phys。修订版X 10，011011（2020）]。创建的多光子非高斯相关性对各种量子信息任务都有吸引力且有用。但是，如何检测和分类多部分非高斯纠缠尚未完全理解。在这里，我们提出了一种实验实用的方法，可以通过引入一类非线性挤压参数来表征连续变量多部分非高斯纠缠，涉及涉及相位空间四倍体的高阶高阶矩。由于这些参数可以取决于任意运算符，因此我们考虑对一组实际测量的分析优化，以检测不同类别的多部分非高斯纠缠，范围从完全可分离到完全不可分割。我们证明，非线性挤压参数是对量子渔民在可访问的三阶矩中的极好近似。非线性挤压水平量化了那些纠缠状态提供的计量学优势。此外，通过分析上述实验，我们表明我们的方法可以很容易地用于确认完全不可分割的三方非高斯纠缠状态，通过执行有限数量的测量值，而无需完全了解量子状态。
Very recently, strongly non-Gaussian states have been observed via a direct three-mode spontaneous parametric down-conversion in a superconducting cavity [Phys. Rev. X 10, 011011 (2020)]. The created multi-photon non-Gaussian correlations are attractive and useful for various quantum information tasks. However, how to detect and classify multipartite non-Gaussian entanglement has not yet been completely understood. Here, we present an experimentally practical method to characterize continuous-variable multipartite non-Gaussian entanglement, by introducing a class of nonlinear squeezing parameters involving accessible higher-order moments of phase-space quadratures. As these parameters can depend on arbitrary operators, we consider their analytical optimization over a set of practical measurements, in order to detect different classes of multipartite non-Gaussian entanglement ranging from fully separable to fully inseparable. We demonstrate that the nonlinear squeezing parameters act as an excellent approximation to the quantum Fisher information within accessible third-order moments. The level of the nonlinear squeezing quantifies the metrological advantage provided by those entangled states. Moreover, by analyzing the above mentioned experiment, we show that our method can be readily used to confirm fully inseparable tripartite non-Gaussian entangled states by performing a limited number of measurements without requiring full knowledge of the quantum state.
