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arXiv 2102.06193quant-phmath.OC
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维格纳负性的见证

Witnessing Wigner Negativity

Ulysse Chabaud, Pierre-Emmanuel Emeriau, Frédéric Grosshans

摘要:

维格纳函数的负性可以说是量子态最显著的非经典特性之一。除了其基本相关性之外,它也是连续变量量子加速的必要资源。随着量子技术的出现,识别和表征相对于现有经典技术具有优势的资源的需求变得更加迫切。在这里,我们推导出证人的维格纳负性的单模和多模量子态,根据与福克态,这可以可靠地测量使用标准的检测设置的结晶。它们具有一个阈值期望值,指示所测量的状态是否具有负维格纳函数。此外,违反的数量提供了一个操作量化的维格纳负性。我们将为我们的证人找到阈值的问题称为无限维线性优化问题。通过放松和限制相应的线性规划,我们得到两个收敛的半定规划,这提供了越来越严格的上限和下限的阈值的数值序列。我们进一步表明,我们的证人形成一个完整的家庭-每个维格纳负态被检测到至少一个证人-从而提供了一个可靠的方法,从实验上见证维格纳负性的量子态从几个测量。从基础的角度来看,我们的研究结果提供了一套积极的维格纳函数,仍然缺乏一个适当的表征的见解。

英文摘要:

Negativity of the Wigner function is arguably one of the most striking non-classical features of quantum states. Beyond its fundamental relevance, it is also a necessary resource for quantum speedup with continuous variables. As quantum technologies emerge, the need to identify and characterize the resources which provide an advantage over existing classical technologies becomes more pressing. Here we derive witnesses for Wigner negativity of single-mode and multimode quantum states, based on fidelities with Fock states, which can be reliably measured using standard detection setups. They possess a threshold expectation value indicating whether the measured state has a negative Wigner function. Moreover, the amount of violation provides an operational quantification of Wigner negativity. We phrase the problem of finding the threshold values for our witnesses as an infinite-dimensional linear optimisation problem. By relaxing and restricting the corresponding linear programs, we derive two converging hierarchies of semidefinite programs, which provide numerical sequences of increasingly tighter upper and lower bounds for the threshold values. We further show that our witnesses form a complete family - each Wigner negative state is detected by at least one witness - thus providing a reliable method for experimentally witnessing Wigner negativity of quantum states from few measurements. From a foundational perspective, our findings provide insights on the set of positive Wigner functions which still lacks a proper characterisation.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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