《自然》（20230223出版）一周论文导读

编译 | 李言

Nature, 23 February 2023, Volume 614 Issue 7949

《自然》2023年2月23日，第614卷，7949期

天文学Astronomy

Identification of carbon dioxide in an exoplanet atmosphere

系外行星大气中二氧化碳的识别

▲ 作者：JWST Transiting Exoplanet Community Early Release Science Team

▲ 链接：

https://www.nature.com/articles/s41586-022-05269-w

▲ 摘要：

在这里，我们介绍由詹姆斯•韦布空间望远镜（JWST）透射光谱观测中发现的热气体巨星WASP-39b大气中二氧化碳的检测。

本研究中使用的数据波长跨度为3.0-5.5微米，在4.3微米处展示了明显的二氧化碳吸收特征。整个光谱与一维的10倍太阳金属丰度模型十分匹配，该模型假设辐射-对流-热化学平衡，并具有中等的云不透明度。

模型预测，除二氧化碳之外，大气中应该有水、一氧化碳和硫化氢，以及极少的甲烷。此外，我们还试探性地检测到一个在4.0微米附近的细微吸收特征，但模型没有再现。

▲ Abstract：

Here we present the detection of CO2 in the atmosphere of the gas giant exoplanet WASP-39b from transmission spectroscopy observations obtained with JWST as part of the Early Release Science programme. The data used in this study span 3.0–5.5 micrometres in wavelength and show a prominent CO2 absorption feature at 4.3 micrometres (26-sigma significance). The overall spectrum is well matched by one-dimensional, ten-times solar metallicity models that assume radiative–convective–thermochemical equilibrium and have moderate cloud opacity. These models predict that the atmosphere should have water, carbon monoxide and hydrogen sulfide in addition to CO2, but little methane. Furthermore, we also tentatively detect a small absorption feature near 4.0 micrometres that is not reproduced by these models.

物理学Physics

Suppressing quantum errors by scaling a surface code logical qubit

通过扩展表面编码逻辑量子位来抑制量子误差

▲ 作者：Google Quantum AI

▲ 链接：

https://www.nature.com/articles/s41586-022-05434-1

▲ 摘要：

在此，我们报告了跨几个代码尺寸的逻辑量子位性能缩放的测试结果，证明了我们的超导量子位系统具有足够的性能来克服增加量子位数量带来的额外误差。我们发现，distance-5逻辑量子位的普遍性能略优于distance-3逻辑量子位，在25个周期及每周期的逻辑错误概率方面。

为了调查破坏性的低概率错误源，我们运行了distance-25的重复代码，并观察到由单个高能事件设置的每个循环层的1.7 × 10−6错误率。模拟实验，提取误差预算，将是未来系统的最大挑战。

这些结果标志着，量子纠错开始随着量子比特数的增加而提高性能，展示达到计算所需的逻辑错误率的之路。

▲ Abstract：

Here we report the measurement of logical qubit performance scaling across several code sizes, and demonstrate that our system of superconducting qubits has sufficient performance to overcome the additional errors from increasing qubit number. We find that our distance-5 surface code logical qubit modestly outperforms an ensemble of distance-3 logical qubits on average, in terms of both logical error probability over 25 cycles and logical error per cycle ((2.914 ± 0.016)% compared to (3.028 ± 0.023)%). To investigate damaging, low-probability error sources, we run a distance-25 repetition code and observe a 1.7 × 10−6 logical error per cycle floor set by a single high-energy event (1.6 × 10−7 excluding this event). We accurately model our experiment, extracting error budgets that highlight the biggest challenges for future systems. These results mark an experimental demonstration in which quantum error correction begins to improve performance with increasing qubit number, illuminating the path to reaching the logical error rates required for computation.

The quantum twisting microscope

量子扭曲显微镜

▲ 作者：A. Inbar, J. Birkbeck, J. Xiao, T. Taniguchi, K. Watanabe, B. Yan, Y. Oreg, Ady Stern, E. Berg & S. Ilani

▲ 链接：

https://www.nature.com/articles/s41586-022-05685-y

▲ 摘要：

在此，我们展示了一种能在其尖端进行局部干涉实验的新型扫描探针显微镜，量子扭曲显微镜（QTM）。QTM基于独特的范德华尖端，允许创建原始的二维异质结，为电子隧穿进入样品提供了大量相干干扰路径。

通过在尖端和样品之间添加一个连续扫描的扭曲角，这种显微镜可以沿着动量空间中的一条线探测电子，类似于扫描隧道显微镜沿着真实空间中的一条线探测电子。

通过一系列实验，我们在尖端展示了室温量子相干，研究了扭曲双层石墨烯的扭曲角演化，并且对单层和扭曲双层石墨烯的能带进行直接成像，最后施加大的局部压力，同时观察到转角双层石墨烯低能带的逐渐变平。QTM为量子材料的新实验开辟了道路。

▲ Abstract：

Here, we demonstrate a conceptually new type of scanning probe microscope—the quantum twisting microscope (QTM)—capable of performing local interference experiments at its tip. The QTM is based on a unique van der Waals tip, allowing the creation of pristine two-dimensional junctions, which provide a multitude of coherently interfering paths for an electron to tunnel into a sample. With the addition of a continuously scanned twist angle between the tip and sample, this microscope probes electrons along a line in momentum space similar to how a scanning tunnelling microscope probes electrons along a line in real space. Through a series of experiments, we demonstrate room-temperature quantum coherence at the tip, study the twist angle evolution of twisted bilayer graphene, directly image the energy bands of monolayer and twisted bilayer graphene and, finally, apply large local pressures while visualizing the gradual flattening of the low-energy band of twisted bilayer graphene. The QTM opens the way for new classes of experiments on quantum materials.

地球科学Geoscience

Less extreme and earlier outbursts of ice-dammed lakes since 1900

自1900年以来较温和的早期冰坝湖泊爆发

▲ 作者：Georg Veh, Natalie Lützow, Jenny Tamm, Lisa V. Luna, Romain Hugonnet, Kristin Vogel, Marten Geertsema, John J. Clague & Oliver Korup

▲ 链接：

https://www.nature.com/articles/s41586-022-05642-9

▲ 摘要：

在此，通过整理6个主要山区的1569个冰坝失效情况，我们系统地评估了1900年至2021年期间的峰值流量、体积、周期和海拔高度的趋势。我们发现，在这段时间内，6个地区中5个地区的极端峰值流量和流量（最高10%）下降了约一个数量级，而中位数洪水流量下降较少或保持不变。

现在世界各地的冰坝洪水发源于海拔较高的地区，发生时间比1900年提前了大约6个星期。个别反复爆发的冰坝湖泊在规模和发生时间上表现出类似的负趋势，尽管与冰川变薄只有中度相关性。

我们预计，在不久的将来，即使冰川变薄和退缩，冰坝也将继续坍塌。然而，预计到21世纪末，几乎所有地区都将出现广泛的冰川消退，这可能会使大多数火山爆发活动停止。

▲ Abstract：

Here, by collating 1,569 ice-dam failures in six major mountain regions, we systematically assess trends in peak discharge, volume, annual timing and source elevation between 1900 and 2021. We show that extreme peak flows and volumes (10 per cent highest) have declined by about an order of magnitude over this period in five of the six regions, whereas median flood discharges have fallen less or have remained unchanged. Ice-dam floods worldwide today originate at higher elevations and happen about six weeks earlier in the year than in 1900. Inpidual ice-dammed lakes with repeated outbursts show similar negative trends in magnitude and earlier occurrence, although with only moderate correlation to glacier thinning. We anticipate that ice dams will continue to fail in the near future, even as glaciers thin and recede. Yet widespread deglaciation, projected for nearly all regions by the end of the twenty-first century, may bring most outburst activity to a halt.

Severe multi-year drought coincident with Hittite collapse around 1198–1196 BC

约公元前1198-1196年间与赫梯帝国崩溃同时发生的严重多年干旱

▲ 作者：Sturt W. Manning, Cindy Kocik, Brita Lorentzen & Jed P. Sparks

▲ 链接：

https://www.nature.com/articles/s41586-022-05693-y

▲ 摘要：

在此，我们研究了公元前1200年左右赫梯帝国的崩溃。赫梯帝国是跨越五个世纪的古代世界强国之一，其以安纳托利亚半干旱地区为中心，政治和社会经济联系遍及整个古代近东和东地中海，尽管长期面临社会政治、经济和环境挑战，但这也在很长一段时间内证明了帝国的韧性。

对安纳托利亚中部当代杜松树的年轮宽度和稳定同位素记录的检查，提供了高分辨率的干燥记录。该分析确定了公元前1198年至1196年（±3）年间曾存在一个异常严重的连续干旱期，这可能预示了一个临界点，并标志着一种同样可以推翻当代风险缓冲实践的事件。

▲ Abstract：

Here we examine the collapse of the Hittite Empire around 1200 BC. The Hittites were one of the great powers in the ancient world across five centuries, with an empire centred in a semi-arid region in Anatolia with political and socioeconomic interconnections throughout the ancient Near East and Eastern Mediterranean, which for a long time proved resilient despite facing regular and intersecting sociopolitical, economic and environmental challenges. Examination of ring width and stable isotope records obtained from contemporary juniper trees in central Anatolia provides a high-resolution dryness record. This analysis identifies an unusually severe continuous dry period from around 1198 to 1196 (±3) BC, potentially indicating a tipping point, and signals the type of episode that can overwhelm contemporary risk-buffering practices.

生物学Biology

Origination of the modern-style persity gradient 15 million years ago

现代多样性梯度的起源是1500万年前

▲ 作者：Isabel S. Fenton, Tracy Aze, Alexander Farnsworth, Paul Valdes & Erin E. Saupe

▲ 链接：

https://www.nature.com/articles/s41586-023-05712-6

▲ 摘要：

在此，我们以高时空分辨率量化了过去4000万年浮游有孔虫中纬度多样性梯度格局（LDG）的出现，发现现代梯度仅出现在1500万年前。

空间和时间模型表明，浮游有孔虫的LDG可能受水柱物理结构的控制。在1500万年前，随着低纬度垂直温度梯度的增加，纬度温度梯度的突然变陡可能增强了生态位划分，并为低纬度物种形成提供了更多机会。

我们的发现——低纬度物种形成率越高，多样性梯度越陡峭，与浮游有孔虫深度划分的时空模式一致——支持了这一假设。高纬度物种的灭绝也强化了LDG，但这种影响往往比物种形成更弱。我们的研究结论推进了对海洋纬度多样性梯度格局在长时间尺度上的演化的理解。

▲ Abstract：

Here we quantify the emergence of the LDG in planktonic foraminifera at high spatiotemporal resolution over the past 40 million years, finding that a modern-style gradient arose only 15 million years ago. Spatial and temporal models suggest that LDGs for planktonic foraminifera may be controlled by the physical structure of the water column. Steepening of the latitudinal temperature gradient over 15 million years ago, associated with an increased vertical temperature gradient at low latitudes, may have enhanced niche partitioning and provided more opportunities for speciation at low latitudes. Supporting this hypothesis, we find that higher rates of low-latitude speciation steepened the persity gradient, consistent with spatiotemporal patterns of depth partitioning by planktonic foraminifera. Extirpation of species from high latitudes also strengthened the LDG, but this effect tended to be weaker than speciation. Our results provide a step change in understanding the evolution of marine LDGs over long timescales.