Nature, 28 March 2024, Volume 627 Issue 8005

《自然》2024年3月28日，第627卷，8005期

  ?

物理学Physics

A shock flash breaking out of a dusty red supergiant 

布满尘埃的红色超巨星爆发出的冲击波 

▲ 作者：Gaici Li, Maokai Hu, Wenxiong Li, Yi Yang, Xiaofeng Wang, Shengyu Yan, Lei Hu, Jujia Zhang, Yiming Mao, Henrik Riise, Xing Gao, Tianrui Sun, Jialian Liu, Dingrong Xiong, Lifan Wang, Jun Mo, Abdusamatjan Iskandar, Gaobo Xi, Danfeng Xiang, Lingzhi Wang, Guoyou Sun, Keming Zhang, Jian Chen, Weili Lin, Eliot Herman

▲ 链接：

https://www.nature.com/articles/s41586-023-06843-6

▲ 摘要：

爆震辐射是指一颗大质量恒星的核心坍缩爆炸产生的冲击波穿过其外层时产生的光。迄今，最早探测到这种信号是在爆炸发生几小时后，尽管也有报道称发现了其他一些信号。

早期光曲线的时间演变应该提供对激波传播的见解，包括爆炸的不对称性和附近的环境，但这一直受到缺乏多波长观测的阻碍。研究者报告了M101星系中II型超新星（SN 2023ixf）的即时多波段观测，开始于爆炸后约1.4小时。爆炸的恒星是一颗红超巨星，半径约为440太阳半径。

光曲线在1~2小时的时间尺度上迅速演变，并且在最初的几个小时内比模型预测的更暗、更红，研究者将其归因于一个光学厚度的尘埃壳在被冲击波破坏之前。他们推断，爆发和周围尘埃的分布可能不是球对称的。

▲ Abstract：

Shock-breakout emission is light that arises when a shockwave, generated by the core-collapse explosion of a massive star, passes through its outer envelope. Hitherto, the earliest detection of such a signal was at several hours after the explosion1, although a few others had been reported. The temporal evolution of early light curves should provide insights into the shock propagation, including explosion asymmetry and environment in the vicinity, but this has been hampered by the lack of multiwavelength observations. Here we report the instant multiband observations of a type II supernova (SN 2023ixf) in the galaxy M101, beginning at about 1.4?h after the explosion. The exploding star was a red supergiant with a radius of about 440 solar radii. The light curves evolved rapidly, on timescales of 1?2?h, and appeared unusually fainter and redder than predicted by the models9,10,11 within the first few hours, which we attribute to an optically thick dust shell before it was disrupted by the shockwave. We infer that the breakout and perhaps the distribution of the surrounding dust were not spherically symmetric.

The complex circumstellar environment of supernova 2023ixf

超新星2023ixf复杂的星周环境

▲ 作者：E. A. Zimmerman, I. Irani, P. Chen, A. Gal-Yam, S. Schulze, D. A. Perley, J. Sollerman, A. V. Filippenko, T. Shenar, O. Yaron, S. Shahaf, R. J. Bruch, E. O. Ofek, A. De Cia, T. G. Brink, Y. Yang, S. S. Vasylyev, S. Ben Ami, M. Aubert, A. Badash, J. S. Bloom, P. J. Brown, K. De, G. Dimitriadis, K. Zhang

▲ 链接：

https://www.nature.com/articles/s41586-024-07116-6

▲ 摘要：

超新星（SN）的早期演化可以揭示环境和祖恒星的信息。当一颗恒星在真空中爆炸时，从其表面逸出的第一批光子表现为一个短暂的、长达数小时的冲击波爆发耀斑，随后是冷却的发射阶段。

然而，对于在密集的、光学厚度的星周物质（CSM）分布中爆炸的恒星，第一批光子从恒星边缘以外的物质中逸出，初始耀斑的持续时间可以延长到几天，在此期间，逸出的发射表明光球加热。缺乏紫外线（UV）数据的早期偶然观测无法确定早期发射是加热还是冷却，因此无法确定早期爆炸事件的性质。研究者报告了M101星系中SN 2023ixf的紫外光谱。

利用紫外数据以及一套全面的多波长观测，研究者暂时解决了由SN发射加热的厚介质产生爆炸激波的问题，并得出一个可靠的热光度曲线，表明激波从一个半径比典型超巨星大得多的致密层爆发出来。 

▲ Abstract：

The early evolution of a supernova (SN) can reveal information about the environment and the progenitor star. When a star explodes in vacuum, the first photons to escape from its surface appear as a brief, hours-long shock-breakout flare, followed by a cooling phase of emission. However, for stars exploding within a distribution of dense, optically thick circumstellar material (CSM), the first photons escape from the material beyond the stellar edge and the duration of the initial flare can extend to several days, during which the escaping emission indicates photospheric heating. Early serendipitous observations that lacked ultraviolet (UV) data were unable to determine whether the early emission is heating or cooling and hence the nature of the early explosion event. Here we report UV spectra of the nearby SN?2023ixf in the galaxy Messier?101 (M101). Using the UV data as well as a comprehensive set of further multiwavelength observations, we temporally resolve the emergence of the explosion shock from a thick medium heated by the SN emission. We derive a reliable bolometric light curve that indicates that the shock breaks out from a dense layer with a radius substantially larger than typical supergiants. 

Optomechanical realization of the bosonic Kitaev chain

玻色子基塔耶夫链的光力学实现

▲ 作者：Jesse J. Slim, Clara C. Wanjura, Matteo Brunelli, Javier del Pino, Andreas Nunnenkamp & Ewold Verhagen

▲ 链接： 

https://www.nature.com/articles/s41586-024-07174-w

▲ 摘要：

费米子基塔耶夫链是具有拓扑马约拉纳零模的正则模型。研究者报道了在纳米光力学网络中玻色子模拟的实验实现，其中参数相互作用诱导了纳米力学模式之间的分束耦合和双模压缩，分别类似于费米子情况下的跳波和p波配对。这种特殊的结构在玻色子动力学和输运中产生了一系列非同寻常的现象。

研究者观察到正交相关的手性放大，增益与系统尺寸呈指数标度，对边界条件有很强的敏感性。所有这些都与玻色子基塔耶夫链独特的非厄米拓扑性质有关。研究探索了拓扑相变，并通过控制相互作用的相位和振幅揭示了丰富的动态相图。

他们给出了对小扰动的指数增强响应的实验证明，研究结果代表了一种新的合成相的证明，期玻色子动力学不具有费米子的平行性，研究者建立了一个系统来研究非厄米拓扑及其在信号处理和传感中的应用。

▲ Abstract：

The fermionic Kitaev chain is a canonical model featuring topological Majorana zero modes. We report the experimental realization of its bosonic analogue in a nano-optomechanical network, in which the parametric interactions induce beam-splitter coupling and two-mode squeezing among the nanomechanical modes, analogous to hopping and p-wave pairing in the fermionic case, respectively. This specific structure gives rise to a set of extraordinary phenomena in the bosonic dynamics and transport. We observe quadrature-dependent chiral amplification, exponential scaling of the gain with system size and strong sensitivity to boundary conditions. All these are linked to the unique non-Hermitian topological nature of the bosonic Kitaev chain. We probe the topological phase transition and uncover a rich dynamical phase diagram by controlling interaction phases and amplitudes. Finally, we present an experimental demonstration of an exponentially enhanced response to a small perturbation. These results represent the demonstration of a new synthetic phase of matter whose bosonic dynamics do not have fermionic parallels, and we have established a powerful system for studying non-Hermitian topology and its applications for signal manipulation and sensing. 

High-fidelity spin qubit operation and algorithmic initialization above 1 K 

1k以上高保真自旋量子位运算和算法初始化

▲ 作者：Jonathan Y. Huang, Rocky Y. Su, Wee Han Lim, MengKe Feng, Barnaby van Straaten, Brandon Severin, Will Gilbert, Nard Dumoulin Stuyck, Tuomo Tanttu, Santiago Serrano, Jesus D. Cifuentes, Ingvild Hansen, Amanda E. Seedhouse, Ensar Vahapoglu, Ross C. C. Leon, Nikolay V. Abrosimov, Hans-Joachim Pohl, Michael L. W. Thewalt, Fay E. Hudson, Christopher C. Escott, Natalia Ares, Stephen D. Bartlett, Andrea Morello, Andre Saraiva, Chih Hwan Yang

▲ 链接：

 https://www.nature.com/articles/s41586-024-07160-2

▲ 摘要：

在半导体自旋载流子中，编码量子比特已被认为是一种有前途的商业量子计算机方法，可以平版生产和大规模集成。然而，有利的量子应用所需的大量量子位的操作将产生超过毫开尔文温度下低温恒温器可用冷却能力的热负荷。随着规模放大的加速，必须在1 K以上建立容错操作，此时冷却功率要高几个数量级。

研究者在1k以上的硅中调整和操作自旋量子位，其保真度在这些温度下的容错操作所需的范围内。研究者设计了一种算法初始化协议，即使在热能大大高于量子位能量的情况下也可以制备纯双量子位状态，并结合射频读出，使读出和初始化的保真度高达99.34%。

他们还证明了单量子位Clifford门保真度高达99.85%，双量子位门保真度为98.92%。这些进展克服了热能必须远低于量子比特能量才能实现高保真操作的基本限制，克服了可扩展和容错量子计算途径中的主要障碍。

▲ Abstract：

The encoding of qubits in semiconductor spin carriers has been recognized as a promising approach to a commercial quantum computer that can be lithographically produced and integrated at scale. However, the operation of the large number of qubits required for advantageous quantum applications will produce a thermal load exceeding the available cooling power of cryostats at millikelvin temperatures. As the scale-up accelerates, it becomes imperative to establish fault-tolerant operation above 1?K, at which the cooling power is orders of magnitude higher. Here we tune up and operate spin qubits in silicon above 1?K, with fidelities in the range required for fault-tolerant operations at these temperatures. We design an algorithmic initialization protocol to prepare a pure two-qubit state even when the thermal energy is substantially above the qubit energies and incorporate radiofrequency readout to achieve fidelities up to 99.34% for both readout and initialization. We also demonstrate single-qubit Clifford gate fidelities up to 99.85% and a two-qubit gate fidelity of 98.92%. These advances overcome the fundamental limitation that the thermal energy must be well below the qubit energies for the high-fidelity operation to be possible, surmounting a main obstacle in the pathway to scalable and fault-tolerant quantum computation. 

气候学Climatology

Five million years of Antarctic Circumpolar Current strength variability

500万年的南极环极流强度变化

▲ 作者：Frank Lamy, Gisela Winckler, Helge W. Arz, Jesse R. Farmer, Julia Gottschalk, Lester Lembke-Jene, Jennifer L. Middleton, Michèlle van der Does, Ralf Tiedemann, Carlos Alvarez Zarikian, Chandranath Basak, Anieke Brombacher, Levin Dumm, Oliver M. Esper, Lisa C. Herbert, Shinya Iwasaki, Gaston Kreps, Vera J. Lawson, Li Lo, Elisa Malinverno, Alfredo Martinez-Garcia, Elisabeth Michel, Simone Moretti, Christopher M. Moy, Xiangyu Zhao

▲ 链接：

https://www.nature.com/articles/s41586-024-07143-3

▲ 摘要：

南极环极流（ACC）是世界上最大的洋流系统，影响着全球海洋环流、气候和南极冰盖的稳定性。研究者记录了太平洋南部沉积物岩心的ACC强度变化。与全球变冷和全球冰量增加相反，他们发现自530万年前以来，ACC流量没有线性的长期趋势。相反，他们观察到在百万年的时间尺度上，从上新世全球变冷期间ACC强度增加到随后随着早更新世进一步变冷而减少。

ACC制度的这种转变与南大洋的重新配置相吻合，南大洋改变了ACC对大气和海洋强迫的敏感性。研究发现ACC强度变化与40万年偏心周期密切相关，可能源于与热带太平洋温度变率相关的南太平洋急流的岁差变化调制。在中更新世过渡时期首次出现了较弱的ACC流、赤道移动的蛋白石沉积和冰期大气CO₂减少之间的持续联系。最强的ACC流发生在比现在更暖的上新世—更新世时期，这为未来气候变暖可能增加ACC流提供了证据。

▲ Abstract：

The Antarctic Circumpolar Current (ACC) represents the world’s largest ocean-current system and affects global ocean circulation, climate and Antarctic ice-sheet stability. Today, ACC dynamics are controlled by atmospheric forcing, oceanic density gradients and eddy activity. Whereas palaeoceanographic reconstructions exhibit regional heterogeneity in ACC position and strength over Pleistocene glacial–interglacial cycles, the long-term evolution of the ACC is poorly known. Here we document changes in ACC strength from sediment cores in the Pacific Southern Ocean. We find no linear long-term trend in ACC flow since 5.3?million years ago (Ma), in contrast to global cooling9 and increasing global ice volume. Instead, we observe a reversal on a million-year timescale, from increasing ACC strength during Pliocene global cooling to a subsequent decrease with further Early Pleistocene cooling. This shift in the ACC regime coincided with a Southern Ocean reconfiguration that altered the sensitivity of the ACC to atmospheric and oceanic forcings. We find ACC strength changes to be closely linked to 400,000-year eccentricity cycles, probably originating from modulation of precessional changes in the South Pacific jet stream linked to tropical Pacific temperature variability. A persistent link between weaker ACC flow, equatorward-shifted opal deposition and reduced atmospheric CO₂ during glacial periods first emerged during the Mid-Pleistocene Transition (MPT). The strongest ACC flow occurred during warmer-than-present intervals of the Plio-Pleistocene, providing evidence of potentially increasing ACC flow with future climate warming. 

Global supply chains amplify economic costs of future extreme heat risk 

全球供应链放大了未来极端高温风险的经济成本 

▲ 作者：Yida Sun, Shupeng Zhu, Daoping Wang, Jianping Duan, Hui Lu, Hao Yin, Chang Tan, Lingrui Zhang, Mengzhen Zhao, Wenjia Cai, Yong Wang, Yixin Hu, Shu Tao & Dabo Guan

▲ 链接：

https://www.nature.com/articles/s41586-024-07125-5

▲ 摘要：

研究者通过整合气候、流行病学、混合投入产出和可计算的一般均衡全球贸易模型，开发了一个灾害足迹分析框架，以估计本世纪中叶热应激的社会经济影响。他们考虑了与热暴露相关的健康成本、热引起的劳动生产率损失的价值以及由于供应链上的经济中断而造成的间接损失。

研究表明，到2060年，在不同的共同社会经济途径下，预计全球经济损失总额将达到0.6%—4.6%，其中健康损失（37%—45%）、劳动生产率损失（18%—37%）和间接损失（12%—43%）。中南部非洲中小型发展中国家的健康损失（比全球平均水平高2.1至4.0倍）和西非和东南亚的劳动生产率损失（比全球平均水平高2.0至3.3倍）尤其严重。供应链中断的影响更为广泛，中国和美国等以制造业为主的国家受到的冲击更大。

▲ Abstract：

Evidence shows a continuing increase in the frequency and severity of global heatwaves, raising concerns about the future impacts of climate change and the associated socioeconomic costs. Here we develop a disaster footprint analytical framework by integrating climate, epidemiological and hybrid input–output and computable general equilibrium global trade models to estimate the midcentury socioeconomic impacts of heat stress. We consider health costs related to heat exposure, the value of heat-induced labour productivity loss and indirect losses due to economic disruptions cascading through supply chains. Here we show that the global annual incremental gross domestic product loss increases exponentially from 0.03?±?0.01 (SSP?245)–0.05?±?0.03 (SSP?585) percentage points during 2030–2040 to 0.05?±?0.01–0.15?±?0.04 percentage points during 2050–2060. By 2060, the expected global economic losses reach a total of 0.6–4.6% with losses attributed to health loss (37–45%), labour productivity loss (18–37%) and indirect loss (12–43%) under different shared socioeconomic pathways. Small- and medium-sized developing countries suffer disproportionately from higher health loss in South-Central Africa (2.1 to 4.0 times above global average) and labour productivity loss in West Africa and Southeast Asia (2.0–3.3 times above global average). The supply-chain disruption effects are much more widespread with strong hit to those manufacturing-heavy countries such as China and the USA, leading to soaring economic losses of 2.7?±?0.7% and 1.8?±?0.5%, respectively.