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科学网|《自然》（20201022出版）一周论文导读


编译 | 李言
科学网|《自然》（20201022出版）一周论文导读
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天文学Astronomy
Stellar clustering shapes the architecture of planetary systems
恒星群塑造行星系统的结构
▲ 作者：Andrew J. Winter, J. M. Diederik Kruijssen, Steven N. Longmore & Mélanie Chevance
▲ 链接：
▲ 摘要
量化行星系统的结构是如何受到这些环境过程的影响是很有挑战性的 ， 因为恒星群在空间上分散的时间不到10亿年 ， 远低于大多数已知的系外行星的年龄 。
在此 ， 我们在盖亚收集的观测数据中 ， 识别出了围绕系外行星主恒星的旧的、共动的恒星群 ， 并证明了行星系的结构在位置-速度相空间中 ， 对局部恒星群有很强的依赖性 。
在控制了主恒星的年龄、质量、金属丰度和与恒星的距离后 ， 我们得到相空间密度过高（共动恒星数量多于非结构空间）与场在行星系性质上的显著差异（p值为10?5~ 10?2） 。 相空间高密度行星的半长轴和轨道周期中值分别为0.087天文单位和9.6天 ， 而围绕场恒星的行星的半长轴和轨道周期分别为0.81天文单位和154天 。
“热木星”（质量大、周期短的系外行星）主要存在于恒星相空间密度过高的环境中 ， 这表明它们的极端轨道起源于环境的扰动 ， 而不是内部迁移或行星间的散射 。 我们的发现揭示了恒星群是决定行星系结构的关键因素 。
▲ Abstract
It is challenging to quantify how the architecture of planetary sysems is affected by these environmental processes, because stellar groups spatially disperse within less than a billion years, well below the ages of most known exoplanets. Here we identify old, co-moving stellar groups around exoplanet host stars in the astrometric data from the Gaia satellite and demonstrate that the architecture of planetary systems exhibits a strong dependence on local stellar clustering in position-velocity phase space. After controlling for host stellar age, mass, metallicity and distance from the star, we obtain highly significant differences (with p values of10?5to10?2) in planetary system properties between phase space overdensities (composed of a greater number of co-moving stars than unstructured space) and the field. The median semi-major axis and orbital period of planets in phase space overdensities are 0.087 astronomical units and 9.6 days, respectively, compared to 0.81 astronomical units and 154 days, respectively, for planets around field stars. ‘Hot Jupiters’ (massive, short-period exoplanets) predominantly exist in stellar phase space overdensities, strongly suggesting that their extreme orbits originate from environmental perturbations rather than internal migration or planet–planet scattering. Our findings reveal that stellar clustering is a key factor setting the architectures of planetary systems.量子物理Quantum Physics
Integrated optical multi-ion quantum logic
集成光学多离子量子逻辑
▲ 作者：Karan K. Mehta, Chi Zhang, Maciej Malinowski, Thanh-Long Nguyen, Martin Stadler & Jonathan P. Home
▲ 链接：
▲ 摘要
在基本操作的错误率和规模两方面 ， 实用和有用的量子信息处理都需要对现有系统进行实质性的改进 。
在此 ， 我们使用可伸缩光学器件和表面电极离子阱来实现高保真多离子量子逻辑门 ， 这通常是建立精确、大规模量子纠缠的限制因素 ， 而量子纠缠是量子计算的关键 。
光通过多通道上的直接光纤耦合有效地传输到低温环境下的捕集芯片上 ， 从而消除了将光束对准真空系统和低温器的需要 ， 并对振动和波束指向漂移提供了鲁棒性 。 这使得我们可以对离子运动进行基态激光冷却 ， 并实现产生精确性大于99.3(2)%的双离子纠缠态的门 。
这项工作演示了在敏感量子逻辑中可以降低噪音和漂移的硬件 ， 同时为高保真量子处理器的实际并行化提供了途径 。 类似的装置也可能在原子和离子量子传感和计时中得到应用 。
▲ Abstract
Practical and useful quantum information processing requires substantial improvements with respect to current systems, both in the error rates of basic operations and in scale. Here we use scalable optics co-fabricated with a surface-electrode ion trap to achieve high-fidelity multi-ion quantum logic gates, which are often the limiting elements in building up the precise, large-scale entanglement that is essential to quantum computation. Light is efficiently delivered to a trap chip in a cryogenic environment via direct fibre coupling on multiple channels, eliminating the need for beam alignment into vacuum systems and cryostats and lending robustness to vibrations and beam-pointing drifts. This allows us to perform ground-state laser cooling of ion motion and to implement gates generating two-ion entangled states with fidelities greater than 99.3(2) per cent. This work demonstrates hardware that reduces noise and drifts in sensitive quantum logic, and simultaneously offers a route to practical parallelization for high-fidelity quantum processors. Similar devices may also find applications in atom- and ion-based quantum sensing and timekeeping.
Integrated multi-wavelength control of an ion qubit
离子量子位的集成多波长控制
▲ 作者：R. J. Niffenegger, J. Stuart, C. Sorace-Agaskar, D. Kharas, S. Bramhavar, C. D. Bruzewicz, W. Loh, R. T. Maxson, R. McConnell, D. Reens, G. N. West, J. M. Sage & J. Chiaverini
▲ 链接：
▲ 摘要
原子系统控制技术的单片集成是发展量子计算机和便携式量子传感器的一条很有前途的发展道路 。 捕获的原子离子构成了高保真量子信息处理器和高精度光学钟的基础 。
然而 ， 目前的实现依赖于自由空间光学来进行离子控制 ， 这限制了它们的可移植性和可伸缩性 。
在此 ， 我们展示了一个使用集成波导和光栅耦合器的表面电极离子阱芯片 ， 它可以提供电离、冷却、相干操作、量子态制备和锶量子位元检测所需的所有波长的光 。
【科学网|《自然》（20201022出版）一周论文导读】从紫到红外的激光通过光纤阵列耦合到芯片上 ， 创造出固有的稳定光路 ， 我们用它来证明量子位相干性对平台振动的弹性 。
这一CMOS兼容的集成光子表面阱制造、强大的封装和增强的量子比特相干性的演示 ， 是便携式捕获离子量子传感器和时钟发展的关键进展 ， 提供了一种在量子信息处理系统中对大量离子进行完全独立控制的方法 。
▲ Abstract
Monolithic integration of control technologies for atomic systems is a promising route to the development of quantum computers and portable quantum sensors. Trapped atomic ions form the basis of high-fidelity quantum information processors and high-accuracy optical clocks. However, current implementations rely on free-space optics for ion control, which limits their portability and scalability. Here we demonstrate a surface-electrode ion-trap chip using integrated waveguides and grating couplers, which delivers all the wavelengths of light required for ionization, cooling, coherent operations and quantum state preparation and detection ofqubits. Laser light from violet to infrared is coupled onto the chip via an optical-fibre array, creating an inherently stable optical path, which we use to demonstrate qubit coherence that is resilient to platform vibrations. This demonstration of CMOS-compatible integrated photonic surface-trap fabrication, robust packaging and enhanced qubit coherence is a key advance in the development of portable trapped-ion quantum sensors and clocks, providing a way towards the complete, individual control of larger numbers of ions in quantum information processing systems.材料科学Material Science
Filling metal–organic framework mesopores withCO2photoreduction二氧化钛在金属有机框架中介孔的填充及二氧化碳光还原
▲ 作者：Zhuo Jiang, Xiaohui Xu, Yanhang Ma, Hae Sung Cho, Deng Ding, Chao Wang, Jie Wu, Peter Oleynikov, Mei Jia, Jun Cheng, Yi Zhou, Osamu Terasaki, Tianyou Peng, Ling Zan & Hexiang Deng
▲ 链接：
▲ 摘要
金属有机框架（MOFs）因其与气体分子的特殊相互作用而闻名；并且 ， 它们丰富有序的孔隙度 ， 使它们有希望成为光催化气体分子转化为有用产品的候选者 。
然而 ， 尝试使用MOFs或基于MOF的复合材料进行二氧化碳光还原通常会导致二氧化碳转化效率远远低于从最先进的固态或分子催化剂 ， 即使是在牺牲试剂的促进下 。
在此 ， 我们通过在以对苯二甲酸铬为基础的MOF（MIL-101）及其衍生物的不同孔隙中生长二氧化钛 ， 在MOF晶体中创建“分子隔间” 。 这使得光吸收/电子生成二氧化钛单元和MOFs主干中的催化金属簇之间能够协同工作 ， 从而促进光催化二氧化钛减排 ， 同时产生氧气 。
在波长为350纳米的复合材料中 ， 观察到二氧化碳光还原的表观量子效率为11.3% ， 该复合材料由42%的MIL-101衍生物二氧化钛组成 ， 即42%-TiO2Metal–organic frameworks (MOFs) are known for their specific interactions with gas molecules; this, combined with their rich and ordered porosity, makes them promising candidates for the photocatalytic conversion of gas molecules to useful products. However, attempts to use MOFs or MOF-based composites forCO2 photoreduction usually result in far lowerCO2conversion efficiency than that obtained from state-of-the-art solid-state or molecular catalysts, even when facilitated by sacrificial reagents. Here we create ‘molecular compartments’ inside MOF crystals by growingTiO2inside different pores of a chromium terephthalate-based MOF (MIL-101) and its derivatives. This allows for synergy between the light-absorbing/electron-generatingTiO2units and the catalytic metal clusters in the backbones of MOFs, and therefore facilitates photocatalyticCO2reduction, concurrent with production ofO2. An apparent quantum efficiency forCO2photoreduction of 11.3 per cent at a wavelength of 350 nanometres is observed in a composite that consists of 42 per centTiO2in a MIL-101 derivative, namely,42%-TiO2Seismic evidence for partial melt below tectonic plates
地壳构造板块下部分融化的地震学证据
▲ 作者：Eric Debayle, Thomas Bodin, Stéphanie Durand & Yanick Ricard
▲ 链接：
▲ 摘要
上地幔的地震低速带（LVZ）通常与低粘性软流圈相联系 ， 软流圈在构造板块与地幔的解耦中起着关键作用 。 然而 ， 低速带的起源尚不清楚 。
在解释全球三维剪切衰减和速度模型的基础上 ， 我们在此报告在低速带内发生的部分熔融 。 我们观察到 ， 海洋中部山脊下150-200公里处的部分融化 ， 主要热点和弧后区域为软流圈提供了支撑 。
其中一小部分（不到0.30%）仍然被困在海洋低速带中 。 在大陆区域下几乎没有熔体 。 熔融量随板速的增加而增加 ， 当板速在每年3厘米至5厘米之间时 ， 熔融量显著增加 。
这一发现与以前在构造板块下面观察到的地幔晶体排列一致 。 我们的观察表明 ， 通过降低黏度 ， 熔融有利于板块运动和软流圈中的大规模晶体排列 。
▲ Abstract
The seismic low-velocity zone (LVZ) of the upper mantle is generally associated with a low-viscosity asthenosphere that has a key role in decoupling tectonic plates from the mantle. However, the origin of the LVZ remains unclear. On the basis of the interpretation of global three-dimensional shear attenuation and velocity models, here we report partial melt occurring within the LVZ. We observe that partial melting down to 150–200 kilometres beneath mid-ocean ridges, major hotspots and back-arc regions feeds the asthenosphere. A small part of this melt (less than 0.30 per cent) remains trapped within the oceanic LVZ. Melt is mostly absent under continental regions. The amount of melt increases with plate velocity, increasing substantially for plate velocities of between 3 centimetres per year and 5 centimetres per year. This finding is consistent with previous observations of mantle crystal alignment underneath tectonic plates. Our observations suggest that by reducing viscosity melt facilitates plate motion and large-scale crystal alignment in the asthenosphere.
医学Medicine
Immune-evasive human islet-like organoids ameliorate diabetes
屏蔽免疫系统的人胰岛类器官改善糖尿病
▲ 作者：Eiji Yoshihara, Carolyn O’Connor, Emanuel Gasser, Zong Wei, Tae Gyu Oh, Tiffany W. Tseng, Dan Wang, et al.
▲ 链接：
▲ 摘要
从干细胞中提取的胰岛有望作为胰岛素依赖性糖尿病的治疗手段 ， 但实现这一目标仍面临挑战 。
在此 ， 我们从诱导的多能干细胞中生成人胰岛样器官类（HILOs） ， 并证明非典型WNT4信号驱动了强健的体外葡萄糖刺激胰岛素分泌所必需的代谢成熟 。 这些功能成熟的肝细胞含有内分泌样细胞类型 ， 在移植后 ， 能迅速恢复糖尿病NOD/SCID小鼠的葡萄糖稳态 。
免疫检查点蛋白程序性死亡配体1 (PD-L1)的过表达保护了HILO异种移植物 ， 使免疫状态的糖尿病小鼠连续50天控制血糖 。 此外 ， 干扰素在体外刺激可诱导内源性PD-L1表达 ， 并限制T细胞的激活和移植物排斥反应 。
葡萄糖反应胰岛样有机体的产生能够屏蔽免疫系统 ， 提供了一个有潜力替代依赖性方法治疗糖尿病的方式 。
▲ Abstract
Islets derived from stem cells hold promise as a therapy for insulin-dependent diabetes, but there remain challenges towards achieving this goal. Here we generate human islet-like organoids (HILOs) from induced pluripotent stem cells and show that non-canonical WNT4 signalling drives the metabolic maturation necessary for robust ex vivo glucose-stimulated insulin secretion. These functionally mature HILOs contain endocrine-like cell types that, upon transplantation, rapidly re-establish glucose homeostasis in diabetic NOD/SCID mice. Overexpression of the immune checkpoint protein programmed death-ligand 1 (PD-L1) protected HILO xenografts such that they were able to restore glucose homeostasis in immune-competent diabetic mice for 50 days. Furthermore, ex vivo stimulation with interferon-γ induced endogenous PD-L1 expression and restricted T cell activation and graft rejection. The generation of glucose-responsive islet-like organoids that are able to avoid immune detection provides a promising alternative to cadaveric and device-dependent therapies in the treatment of diabetes.
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