《自然》（20230406出版）一周论文导读
2023/4/8 20:04:35 科学网
编译 | 李言
Nature, 6 April 2023, Volume 616 Issue 7955
《自然》2023年4月6日，第616卷，7955期
物理学Physics
Beating the break-even point with a discrete-variable-encoded logical qubit
用离散变量编码的逻辑量子位打破盈亏平衡点
▲ 作者：Zhongchu Ni, Sai Li, Xiaowei Deng, Yanyan Cai et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-05784-4
▲ 摘要：
在此，我们展示了一个电路量子电动力学架构中的量子纠错过程，其中逻辑量子位以微波腔的光子数状态二项编码，色散耦合到辅助超导量子位。
通过将具有定制频率梳的脉冲应用于辅助量子位，我们可以重复地高保真地提取错误综合征，并相应地使用反馈控制进行错误校正，从而超过盈亏平衡点 16%。我们的工作展示了高效的离散变量编码在容错量子计算中的潜力。
▲ Abstract：
Here we demonstrate a QEC procedure in a circuit quantum electrodynamics architecture, where the logical qubit is binomially encoded in photon-number states of a microwave cavity, dispersively coupled to an auxiliary superconducting qubit. By applying a pulse featuring a tailored frequency comb to the auxiliary qubit, we can repetitively extract the error syndrome with high fidelity and perform error correction with feedback control accordingly, thereby exceeding the break-even point by about 16% lifetime enhancement. Our work illustrates the potential of hardware-efficient discrete-variable encodings for fault-tolerant quantum computation.
材料科学Material science
Deforming lanthanum trihydride for superionic conduction
氢化镧畸变下的超离子传导
▲ 作者：Weijin Zhang, Jirong Cui, Shangshang Wang, Hujun Cao, Anan Wu, Yuanhua Xia, Qike Jiang, Jianping Guo, Teng He & Ping Chen
▲ 链接：
https://www.nature.com/articles/s41586-023-05815-0
▲ 摘要：
氢化物离子(H?)具有较强的还原性和较高的氧化还原电位，是一种活性氢及能量载体。在此，我们展示了通过在氢化镧晶格中创造纳米大小的颗粒和晶格缺陷，其电子传导性可以被抑制超过五个数量级。
这使得氢化镧成为在?40°C的条件下、氢负离子电导率高达10?2?S/?cm?1，活化能仅为0.12 eV的超离子导体。由此，我们也展示了一种室温全固态氢化物电池。
▲ Abstract：
With strong reducibility and high redox potential, the hydride ion (H?) is a reactive hydrogen species and an energy carrier. Here we show that by creating nanosized grains and defects in the lattice, the electronic conductivity of LaHx can be suppressed by more than five orders of magnitude. This transforms LaHx to a superionic conductor at ?40?°C with a record high H? conductivity of 1.0?×?10?2?S?cm?1 and a low diffusion barrier of 0.12?eV. A room-temperature all-solid-state hydride cell is demonstrated.
Gate-tunable heavy fermions in a moiré Kondo lattice
莫尔近藤晶格中的门可调谐重费米子
▲ 作者：Wenjin Zhao, Bowen Shen et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-05800-7
▲ 摘要：
在此，我们报告了在AB -堆叠的MoTe2/WSe2 moiré双分子层中合成近藤晶格的实现，其中MoTe2层被调谐到Mott绝缘状态，支持局部矩的三角形moiré晶格，WSe2层中掺杂了漫游传导载流子。
我们观察到重费米子在近藤温度以下具有较大的费米表面。我们还观察到外部磁场对重费米子的破坏，以至于费米表面尺寸和准粒子质量急剧下降。我们进一步通过漫游传导载流子密度或近藤相互作用证明了广泛和连续的门可调的近藤温度。
我们的研究开启了在基于半导体moiré材料的单个器件中，实现现场访问具有奇异量子临界的近藤晶格相图的可能性。
▲ Abstract：
Here we report the realization of a synthetic Kondo lattice in AB-stacked MoTe2/WSe2 moiré bilayers, in which the MoTe2 layer is tuned to a Mott insulating state, supporting a triangular moiré lattice of local moments, and the WSe2 layer is doped with itinerant conduction carriers. We observe heavy fermions with a large Fermi surface below the Kondo temperature. We also observe the destruction of the heavy fermions by an external magnetic field with an abrupt decrease in the Fermi surface size and quasi-particle mass. We further demonstrate widely and continuously gate-tunable Kondo temperatures through either the itinerant carrier density or the Kondo interaction. Our study opens the possibility of in situ access to the phase diagram of the Kondo lattice with exotic quantum criticalities in a single device based on semiconductor moiré materials.
地球科学Earth Science
Lunar eclipses illuminate timing and climate impact of medieval volcanism
月食阐明中世纪火山活动的时间和气候影响
▲ 作者：Sébastien Guillet, Christophe Corona, Clive Oppenheimer et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-05751-z
▲ 摘要：
在此，我们利用对当代月全食报告的分析，得出了平流层浑浊度的时间序列，从而得到了对中世纪盛期(HMP)火山爆发活动的新认识。通过将这一新记录与气溶胶模型模拟和基于树木年轮的气候数据相结合，我们修正了五次著名火山爆发的日期，并将每一次爆发都与平流层气溶胶层联系起来。
此后的五次火山爆发——包括大约公元1182年格陵兰岛上空高硫沉积的那一次——只影响对流层，对气候的影响不大。我们的研究结果为进一步研究火山爆发的十年至百年尺度气候响应提供了支持。
▲ Abstract：
Here we shed new light on explosive volcanism during the HMP, drawing on analysis of contemporary reports of total lunar eclipses, from which we derive a time series of stratospheric turbidity. By combining this new record with aerosol model simulations and tree-ring-based climate proxies, we refine the estimated dates of five notable eruptions and associate each with stratospheric aerosol veils. Five further eruptions, including one responsible for high sulfur deposition over Greenland circa 1182?CE, affected only the troposphere and had muted climatic consequences. Our findings offer support for further investigation of the decadal-scale to centennial-scale climate response to volcanic eruptions.
农业Argriculture
Ageing threatens sustainability of smallholder farming in China
老龄化影响中国小农农业的可持续性
▲ 作者：Chenchen Ren, Xinyue Zhou, Chen Wang, Yaolin Guo, Yu Diao, Sisi Shen, Stefan Reis, Wanyue Li, Jianming Xu & Baojing Gu
▲ 链接：
https://www.nature.com/articles/s41586-023-05738-w
▲ 摘要：
在此，通过利用中国1.5万多户有作物但没有牲畜的农村家庭的数据，我们发现，在2019年农村人口老龄化通过转移耕地所有权和撂荒土地(约400万公顷)使农田规模减少了4%，以1990年的人口年龄结构为基准。
这些变化导致包括化肥、粪肥和机械在内的农业投入减少，农业产出和劳动生产率分别下降了5%和4%，农民收入降低了15%。同时，化肥损失增加了3%，导致对环境的污染物排放增加。在新的农业模式中，如合作农业，农场往往更大且由年轻的农民经营。他们的平均教育水平更高，因此能改善农业管理。
通过鼓励向新的农业模式过渡，可以人口扭转老龄化的负面后果。与2020年相比，2100年的农业投入、农田规模和农民收入将分别增长约14%、20%和26%，化肥损失将减少4%。这表明对农村人口老龄化的管理将有助于中国小农农业向可持续农业转变。
▲ Abstract：
Here, by using data from more than 15,000 rural households with crops but no livestock across China, we show that rural population ageing reduced farm size by 4% through transferring cropland ownership and land abandonment (approximately 4 million hectares) in 2019, taking the population age structure in 1990 as a benchmark. These changes led to a reduction of agricultural inputs, including chemical fertilizers, manure and machinery, which decreased agricultural output and labour productivity by 5% and 4%, respectively, further lowering farmers’ income by 15%. Meanwhile, fertilizer loss increased by 3%, resulting in higher pollutant emissions to the environment. In new farming models, such as cooperative farming, farms tend to be larger and operated by younger farmers, who have a higher average education level, hence improving agricultural management. By encouraging the transition to new farming models, the negative consequences of ageing can be reversed. Agricultural input, farm size and farmer’s income would grow by approximately 14%, 20% and 26%, respectively, and fertilizer loss would reduce by 4% in 2100 compared with that in 2020. This suggests that management of rural ageing will contribute to a comprehensive transformation of smallholder farming to sustainable agriculture in China.
Four ways blue foods can help achieve food system ambitions across nations
海洋食品可以帮助各国实现粮食体系目标的4种途径
▲ 作者：Beatrice I. Crona, Emmy Wassénius, Malin Jonell et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-05737-x
▲ 摘要：
在此，我们整合了此前的发现并将其转化为4个政策目标，以帮助实现海洋食品对世界各国粮食体系的贡献：确保关键营养的供应，提供陆地肉类的健康替代品，减少饮食的环境足迹，并确保海洋食品在气候变化下对营养、经济和生计的贡献。
为了解释具体环境、社会经济和文化如何影响这一目标，我们评估了每个政策目标在不同国家的相关性，并在国家和国际范围内研究了相关的共同利益和交易。我们发现，在许多非洲和南美国家，促进与文化相关的海洋食品的消费，可以解决维生素B12和omega-3缺乏的问题，特别尤其是在营养不良的人群中。
同时，在许多北方国家，通过适度食用对环境影响较小的海产品，可以降低心血管疾病发病率和反刍动物肉类摄入造成的大量温室气体足迹。
▲ Abstract：
Here we integrate these findings and translate them into four policy objectives to help realize the contributions that blue foods can make to national food systems around the world: ensuring supplies of critical nutrients, providing healthy alternatives to terrestrial meat, reducing dietary environmental footprints and safeguarding blue food contributions to nutrition, just economies and livelihoods under a changing climate. To account for how context-specific environmental, socio-economic and cultural aspects affect this contribution, we assess the relevance of each policy objective for individual countries, and examine associated co-benefits and trade-offs at national and international scales. We find that in many African and South American nations, facilitating consumption of culturally relevant blue food, especially among nutritionally vulnerable population segments, could address vitamin B12 and omega-3 deficiencies. Meanwhile, in many global North nations, cardiovascular disease rates and large greenhouse gas footprints from ruminant meat intake could be lowered through moderate consumption of seafood with low environmental impact.
编辑 | 方圆
排版 | 郭刚
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投稿事宜：tougao@stimes.cn
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