论文标题

连续变量量子系统的经典影子层析成像

Classical shadow tomography for continuous variables quantum systems

论文作者

Becker, Simon, Datta, Nilanjana, Lami, Ludovico, Rouzé, Cambyse

论文摘要

在本文中,我们开发了一个连续变量(CV)阴影层析成像方案,并在量子光学中具有广泛的应用。我们的工作是由CV系统在量子信息,量子通信,量子传感,量子模拟,量子计算和误差校正中的实验和技术相关性提高所激发的。我们介绍了两种可实现的方案,用于仅使用随机高斯单位和易于实现的高斯测量值,例如同源性和异差检测,从而获得了CV(可能是非高斯)量子状态的经典阴影。对于这两个方案,我们都表明$ n = o \ big(\ peratatorName {poly} \ big(\ frac {1}ε,\ log \ big \ big(\ frac {1}Δ\ big),m_n^{r+α}只要状态$ρ$具有$ n>α$ bimy $ m_n $的订单$ρ$,均具有高概率$ 1-δ$和准确性$ 1- $ $ 1-Δ$和准确性$α$的任何$ r $ - 局部多项式的价值。通过同时将能源和相空间中的状态和运营商截断,我们能够克服由于简历系统的无限二维引起的新数学挑战。我们还提供了一个方案来学习国家的非线性功能,例如任何少数模式的熵,通过利用最近的能量约束的熵连续性边界。最后,我们提供了在量子信息理论中相关性的CV状态的情况下,我们提供了数值证据,包括多体系统和CAT量子状态的二次汉密尔顿人的基础状态。我们希望我们的计划在学习2D材料和光子晶体的相关状态方面提供良好的恢复。

In this article we develop a continuous variable (CV) shadow tomography scheme with wide ranging applications in quantum optics. Our work is motivated by the increasing experimental and technological relevance of CV systems in quantum information, quantum communication, quantum sensing, quantum simulations, quantum computing and error correction. We introduce two experimentally realisable schemes for obtaining classical shadows of CV (possibly non-Gaussian) quantum states using only randomised Gaussian unitaries and easily implementable Gaussian measurements such as homodyne and heterodyne detection. For both schemes, we show that $N=O\big(\operatorname{poly}\big(\frac{1}ε,\log\big(\frac{1}δ\big),M_n^{r+α},\log(m)\big)\big)$ samples of an unknown $m$-mode state $ρ$ suffice to learn the expected value of any $r$-local polynomial in the canonical observables of degree $α$, both with high probability $1-δ$ and accuracy $ε$, as long as the state $ρ$ has moments of order $n>α$ bounded by $M_n$. By simultaneously truncating states and operators in energy and phase space, we are able to overcome new mathematical challenges that arise due to the infinite-dimensionality of CV systems. We also provide a scheme to learn nonlinear functionals of the state, such as entropies over any small number of modes, by leveraging recent energy-constrained entropic continuity bounds. Finally, we provide numerical evidence of the efficiency of our protocols in the case of CV states of relevance in quantum information theory, including ground states of quadratic Hamiltonians of many-body systems and cat qubit states. We expect our scheme to provide good recovery in learning relevant states of 2D materials and photonic crystals.

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