《自然》（20240328出版）一周論文導讀

Nature, 28 March 2024, Volume 627 Issue 8005

《自然》2024年3月28日，第627卷，8005期

物理學Physics

A shock flash breaking out of a dusty red supergiant 

布滿塵埃的紅色超巨星爆發出的沖擊波 

▲ 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

▲ 鏈接：

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

▲ 摘要：

爆震輻射是指一顆大質量恒星的核心坍縮爆炸產生的沖擊波穿過其外層時產生的光。迄今，最早探測到這種信號是在爆炸發生幾小時后，盡管也有報道稱發現了其他一些信號。

早期光曲線的時間演變應該提供對激波傳播的見解，包括爆炸的不對稱性和附近的環境，但這一直受到缺乏多波長觀測的阻礙。研究者報告了M101星系中II型超新星（SN 2023ixf）的即時多波段觀測，開始于爆炸后約1.4小時。爆炸的恒星是一顆紅超巨星，半徑約為440太陽半徑。

光曲線在1~2小時的時間尺度上迅速演變，并且在最初的幾個小時內比模型預測的更暗、更紅，研究者將其歸因于一個光學厚度的塵埃殼在被沖擊波破壞之前。他們推斷，爆發和周圍塵埃的分布可能不是球對稱的。

▲ 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復雜的星周環境

▲ 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

▲ 鏈接：

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

▲ 摘要：

超新星（SN）的早期演化可以揭示環境和祖恒星的信息。當一顆恒星在真空中爆炸時，從其表面逸出的第一批光子表現為一個短暫的、長達數小時的沖擊波爆發耀斑，隨后是冷卻的發射階段。

然而，對于在密集的、光學厚度的星周物質（CSM）分布中爆炸的恒星，第一批光子從恒星邊緣以外的物質中逸出，初始耀斑的持續時間可以延長到幾天，在此期間，逸出的發射表明光球加熱。缺乏紫外線（UV）數據的早期偶然觀測無法確定早期發射是加熱還是冷卻，因此無法確定早期爆炸事件的性質。研究者報告了M101星系中SN 2023ixf的紫外光譜。

利用紫外數據以及一套全面的多波長觀測，研究者暫時解決了由SN發射加熱的厚介質產生爆炸激波的問題，并得出一個可靠的熱光度曲線，表明激波從一個半徑比典型超巨星大得多的致密層爆發出來。 

▲ 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

玻色子基塔耶夫鏈的光力學實現

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

▲ 鏈接： 

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

▲ 摘要：

費米子基塔耶夫鏈是具有拓撲馬約拉納零模的正則模型。研究者報道了在納米光力學網絡中玻色子模擬的實驗實現，其中參數相互作用誘導了納米力學模式之間的分束耦合和雙模壓縮，分別類似于費米子情況下的跳波和p波配對。這種特殊的結構在玻色子動力學和輸運中產生了一系列非同尋常的現象。

研究者觀察到正交相關的手性放大，增益與系統尺寸呈指數標度，對邊界條件有很強的敏感性。所有這些都與玻色子基塔耶夫鏈獨特的非厄米拓撲性質有關。研究探索了拓撲相變，并通過控制相互作用的相位和振幅揭示了豐富的動態相圖。

他們給出了對小擾動的指數增強響應的實驗證明，研究結果代表了一種新的合成相的證明，期玻色子動力學不具有費米子的平行性，研究者建立了一個系統來研究非厄米拓撲及其在信號處理和傳感中的應用。

▲ 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運算和算法初始化

▲ 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

▲ 鏈接：

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

▲ 摘要：

在半導體自旋載流子中，編碼量子比特已被認為是一種有前途的商業量子計算機方法，可以平版生產和大規模集成。然而，有利的量子應用所需的大量量子位的操作將產生超過毫開爾文溫度下低溫恒溫器可用冷卻能力的熱負荷。隨著規模放大的加速，必須在1 K以上建立容錯操作，此時冷卻功率要高幾個數量級。

研究者在1k以上的硅中調整和操作自旋量子位，其保真度在這些溫度下的容錯操作所需的范圍內。研究者設計了一種算法初始化協議，即使在熱能大大高于量子位能量的情況下也可以制備純雙量子位狀態，并結合射頻讀出，使讀出和初始化的保真度高達99.34%。

他們還證明了單量子位Clifford門保真度高達99.85%，雙量子位門保真度為98.92%。這些進展克服了熱能必須遠低于量子比特能量才能實現高保真操作的基本限制，克服了可擴展和容錯量子計算途徑中的主要障礙。

▲ 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. 

氣候學Climatology

Five million years of Antarctic Circumpolar Current strength variability

500萬年的南極環極流強度變化

▲ 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

▲ 鏈接：

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

▲ 摘要：

南極環極流（ACC）是世界上最大的洋流系統，影響著全球海洋環流、氣候和南極冰蓋的穩定性。研究者記錄了太平洋南部沉積物巖心的ACC強度變化。與全球變冷和全球冰量增加相反，他們發現自530萬年前以來，ACC流量沒有線性的長期趨勢。相反，他們觀察到在百萬年的時間尺度上，從上新世全球變冷期間ACC強度增加到隨后隨著早更新世進一步變冷而減少。

ACC制度的這種轉變與南大洋的重新配置相吻合，南大洋改變了ACC對大氣和海洋強迫的敏感性。研究發現ACC強度變化與40萬年偏心周期密切相關，可能源于與熱帶太平洋溫度變率相關的南太平洋急流的歲差變化調制。在中更新世過渡時期首次出現了較弱的ACC流、赤道移動的蛋白石沉積和冰期大氣CO₂減少之間的持續聯系。最強的ACC流發生在比現在更暖的上新世—更新世時期，這為未來氣候變暖可能增加ACC流提供了證據。

▲ 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 

全球供應鏈放大了未來極端高溫風險的經濟成本 

▲ 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

▲ 鏈接：

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

▲ 摘要：

研究者通過整合氣候、流行病學、混合投入產出和可計算的一般均衡全球貿易模型，開發了一個災害足跡分析框架，以估計本世紀中葉熱應激的社會經濟影響。他們考慮了與熱暴露相關的健康成本、熱引起的勞動生產率損失的價值以及由于供應鏈上的經濟中斷而造成的間接損失。

研究表明，到2060年，在不同的共同社會經濟途徑下，預計全球經濟損失總額將達到0.6%—4.6%，其中健康損失（37%—45%）、勞動生產率損失（18%—37%）和間接損失（12%—43%）。中南部非洲中小型發展中國家的健康損失（比全球平均水平高2.1至4.0倍）和西非和東南亞的勞動生產率損失（比全球平均水平高2.0至3.3倍）尤其嚴重。供應鏈中斷的影響更為廣泛，中國和美國等以制造業為主的國家受到的沖擊更大。

▲ 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.