标题： 空间量子比特纠缠见证量子自然引力 显示英文标题

标题： Spatial Qubit Entanglement Witness for Quantum Natured Gravity

摘要： 通过两个质量的纠缠来证明引力的量子性质最近被提出。 使用量子比特来见证这种纠缠的方案可以将两个质量拉近到完全1/r相互作用起作用的程度（而不是其二阶泰勒展开式），微米大小的质量相隔10-100微米（无论是否有电磁屏蔽）就足以提供0.01-1赫兹的纠缠增长速率。 然而，迄今为止提出的获取量子比特见证的唯一可行方法是利用嵌入在质量中的自旋，这些自旋的相关性被用来见证在干涉过程中质量之间产生的纠缠。 这带来了双重挑战，一方面需要将保持自旋相干性的方法纳入协议中，另一方面需要对自旋辅助（斯特恩-格拉赫）干涉仪的控制场进行精确控制。 在这里，我们表明，如果能够创建每个质量的不同空间局域态的叠加，无论采用何种方法，仅通过简单的位置相关测量就可以获得质量之间纠缠的空间量子比特见证。 我们发现，在协议的特定阶段出现显著的压缩是其可行性的重要新要求（除了维持空间量子相干性的需求）。 显示英文摘要

摘要： Evidencing the quantum nature of gravity through the entanglement of two masses has recently been proposed. Proposals using qubits to witness this entanglement can afford to bring two masses close enough so that the complete 1/r interaction is at play (as opposed to its second-order Taylor expansion), and micron-sized masses separated by 10-100 microns (with or without electromagnetic screening) suffice to provide a 0.01-1 Hz rate of growth of entanglement. Yet the only viable method proposed for obtaining qubit witnesses so far has been to employ spins embedded in the masses, whose correlations are used to witness the entanglement developed between masses during interferometry. This comes with the dual challenge of incorporating spin coherence-preserving methodologies into the protocol, as well as a demanding precision of control fields for the accurate completion of spin-aided (Stern-Gerlach) interferometry. Here we show that if superpositions of distinct spatially localized states of each mass can be created, whatever the means, simple position correlation measurements alone can yield a spatial qubit witness of entanglement between the masses. We find that a significant squeezing at a specific stage of the protocol is the principal new requirement (in addition to the need to maintain spatial quantum coherence) for its viability