Science, 23 JUN 2023, VOL 380, ISSUE 6651

《科学》2023年6月23日，第380卷，6651期

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物理学Physics

Hunting for Majoranas

寻找马约拉纳准粒子

▲ 作者：Ali Yazdani, Felix von Oppen, Bertrand I. Halperin & Amir Yacoby

▲ 链接：https://www.science.org/doi/10.1126/science.ade0850

▲ 摘要：

在过去十年里，人们付出了相当大的努力，以在新型量子材料和器件中观测非阿贝尔准粒子。这些努力的动机是为了证明超越费米子和玻色子的准粒子的量子统计，并为创建拓扑保护量子比特建立基础科学。

在这篇综述中，研究组聚焦于努力创建具有马约拉纳零模的拓扑超导相。他们考虑了从现有实验工作中吸取的经验教训，这些经验教训推动着对现有平台的改进和新方法的探索。

尽管非阿贝尔准粒子的实验探测仍颇具挑战性，但迄今为止人们所获得的知识和未来机遇，将为量子物理学这一令人兴奋领域的发现和进步提供巨大潜力。

▲ Abstract：

Over the past decade, there have been considerable efforts to observe non-abelian quasiparticles in novel quantum materials and devices. These efforts are motivated by the goals of demonstrating quantum statistics of quasiparticles beyond those of fermions and bosons and of establishing the underlying science for the creation of topologically protected quantum bits. In this Review, we focus on efforts to create topological superconducting phases that host Majorana zero modes. We consider the lessons learned from existing experimental efforts, which are motivating both improvements to present platforms and the exploration of new approaches. Although the experimental detection of non-abelian quasiparticles remains challenging, the knowledge gained thus far and the opportunities ahead offer high potential for discovery and advances in this exciting area of quantum physics.

Mid-circuit correction of correlated phase errors using an array of spectator qubits

利用旁观者量子位阵列对相关相位误差进行中路校正

▲ 作者：K. Singh, C. E. Bradley, S. Anand, V. Ramesh, R. White & H. Bernien.

▲ 链接：https://www.science.org/doi/10.1126/science.ade5337

▲ 摘要：

扩展总是容易出错的量子处理器是一项艰巨挑战。虽然量子纠错最终保证了容错操作，但所需的庞大量子位数和错误阈值令人望而生畏。在一项补充协议中，共置辅助“旁观者”量子位充当噪声的原位探针，并实现对数据量子位错误的实时、相干纠正。

研究组使用铯旁观者量子位阵列来校正铷数据量子位阵列上的相关相位误差。通过结合顺序读出、数据处理和前馈操作，这些相关误差在量子电路的执行中有所降低。

该协议广泛适用于量子信息平台，建立了扩展中性原子量子处理器的关键工具：原子阵列的中路读出、实时处理和前馈，以及原子量子位的相干中路重装。

▲ Abstract：

Scaling up invariably error-prone quantum processors is a formidable challenge. Although quantum error correction ultimately promises fault-tolerant operation, the required qubit overhead and error thresholds are daunting. In a complementary proposal, colocated, auxiliary “spectator” qubits act as in situ probes of noise and enable real-time, coherent corrections of data qubit errors. We used an array of cesium spectator qubits to correct correlated phase errors on an array of rubidium data qubits. By combining in-sequence readout, data processing, and feedforward operations, these correlated errors were suppressed within the execution of the quantum circuit. The protocol is broadly applicable to quantum information platforms and establishes key tools for scaling neutral-atom quantum processors: mid-circuit readout of atom arrays, real-time processing and feedforward, and coherent mid-circuit reloading of atomic qubits.

材料科学Materials Science

Superconducting vortices carrying a temperature-dependent fraction of the flux quantum

携带通量量子温度相关分数的超导涡旋

▲ 作者：Yusuke Iguchi, Kunihiro Kihou, Chul-Ho Lee, Mats Barkman, Andrea L. Benfenati, Vadim Grinenko, et al.

▲ 链接：https://www.science.org/doi/10.1126/science.abp9979

▲ 摘要：

磁场通过形成量子涡旋（包围的磁通量等于磁通量量子）穿透II型体超导体。磁通量量子是一个只依赖于基本常数的普适量。

研究组使用扫描超导量子干涉装置（SQUID）磁强计研究了空穴过掺杂Ba1?xKxFe2As2 （x = 0.77）中的孤立涡旋。在许多地方，研究组观察到的涡旋只携带部分磁通量量子，其大小随温度连续变化。

研究组展示了这些涡旋的可移动性和可操纵性，并将其解释为具有非普适量子化（分数）磁通量的量子涡旋，其大小由多组分超导体的温度相关参数决定。

▲ Abstract：

Magnetic field penetrates type-II bulk superconductors by forming quantum vortices that enclose a magnetic flux equal to the magnetic flux quantum. The flux quantum is a universal quantity that depends only on fundamental constants. In this study, we investigated isolated vortices in the hole-overdoped Ba1?xKxFe2As2  (x = 0.77) by using scanning superconducting quantum interference device (SQUID) magnetometry. In many locations, we observed objects that carried only part of a flux quantum, with a magnitude that varied continuously with temperature. We demonstrated mobility and manipulability of these objects and interpreted them as quantum vortices with nonuniversally quantized (fractional) magnetic flux whose magnitude is determined by the temperature-dependent parameters of a multicomponent superconductor.

Deformable hard tissue with high fatigue resistance in the hinge of bivalve Cristaria plicata

双壳纲褶纹冠蚌铰链中具有高抗疲劳性的可变形硬组织

▲ 作者：Xiang-Sen Meng, Li-Chuan Zhou, Lei Liu, Yin-Bo Zhu, Yu-Feng Meng, Dong-Chang Zheng, et al.

▲ 链接：https://www.science.org/doi/10.1126/science.ade2038

▲ 摘要：

双壳纲动物的外壳铰链在其一生中可承受数十万次重复的双壳开合运动。

研究组探讨了双壳纲褶纹冠蚌铰链中矿化组织的分层设计，这使得组织具有可变形性和抗疲劳性，从而奠定了重复运动能力的基础。这种折叠的扇形组织由嵌入弹性基质中的径向排列的脆性文石纳米线组成，可将外部径向载荷转化为周向变形。

软硬复合微观结构可抑制组织内的应力集中。沿纳米线纵向方向的相干纳米孪晶界增加了其抗弯曲断裂的能力。这种不寻常的生物矿物通过多尺度结构设计利用了每种成分的固有特性，为抗疲劳结构材料的演变提供了新见解。

▲ Abstract：

The hinge of bivalve shells can sustain hundreds of thousands of repeating opening-and-closing valve motions throughout their lifetime. We studied the hierarchical design of the mineralized tissue in the hinge of the bivalve Cristaria plicata, which endows the tissue with deformability and fatigue resistance and consequently underlies the repeating motion capability. This folding fan–shaped tissue consists of radially aligned, brittle aragonite nanowires embedded in a resilient matrix and can translate external radial loads to circumferential deformation. The hard-soft complex microstructure can suppress stress concentration within the tissue. Coherent nanotwin boundaries along the longitudinal direction of the nanowires increase their resistance to bending fracture. The unusual biomineral, which exploits the inherent properties of each component through multiscale structural design, provides insights into the evolution of antifatigue structural materials.

化学Chemistry

Facile mechanochemical cycloreversion of polymer cross-linkers enhances tear resistance

聚合物交联剂的简易机械化学裂环增强了抗撕裂性

▲ 作者：Shu Wang, Yixin Hu, Tatiana B. Kouznetsova, Liel Sapir, Danyang Chen, Abraham Herzog-Arbeitman, et al.

▲ 链接：https://www.science.org/doi/10.1126/science.adg3229

▲ 摘要：

共价聚合物网络的机械性能通常源于聚合物链的永久末端连接或交联，更容易断裂的分子连接物可能会产生撕裂所需能量更少的材料。

研究组报道称，基于环丁烷的力敏基团交联剂突破了力触发的裂环作用，产生的聚合物网络韧性是传统类似物的九倍。这种反应归因于长而强的主聚合物链和交联剂剪切力的结合，在相同时间尺度下，这些力比对照交联剂小约五倍。

增强的韧性没有与非共价交联相关的滞后现象，且在两种不同的丙烯酸酯弹性体中，在疲劳和恒定位移速率张力下，以及在凝胶和弹性体中均观察到该韧性。

▲ Abstract：

The mechanical properties of covalent polymer networks often arise from the permanent end-linking or cross-linking of polymer strands, and molecular linkers that break more easily would likely produce materials that require less energy to tear. We report that cyclobutane-based mechanophore cross-linkers that break through force-triggered cycloreversion lead to networks that are up to nine times as tough as conventional analogs. The response is attributed to a combination of long, strong primary polymer strands and cross-linker scission forces that are approximately fivefold smaller than control cross-linkers at the same timescales. The enhanced toughness comes without the hysteresis associated with noncovalent cross-linking, and it is observed in two different acrylate elastomers, in fatigue as well as constant displacement rate tension, and in a gel as well as elastomers.

地球科学Earth Science

Large herbivore diversity slows sea ice–associated decline in arctic tundra diversity

大型食草动物的多样性减缓了北极苔原海冰相关的多样性下降

▲ 作者：Eric Post, Elina Kaarlej?rvi, Marc Macias-Fauria, David A. Watts, Pernille Sporon B?ving, Sean M. P. Cahoon, et al.

▲ 链接：https://www.science.org/doi/10.1126/science.add2679

▲ 摘要：

由于包括气候强迫在内的多种人类压力因素，全球生物多样性正在下降。然而，局部多样性趋势在某些分类群中并不一致，模糊了局部过程对全球模式的贡献。

在一项为期15年的实验中，随着气候变暖，包括植物、真菌和地衣的北极苔原多样性有所下降，已知会影响苔原植被组成的大型食草动物被排除在外。由于生长季的背景温度随着海冰的减少而上升，无论实验处理如何，苔原多样性都在下降。

然而，有大型食草动物时，多样性下降的速度比没有大型食草动物时慢。这种差异与大型食草动物有效多样性的增加有关，因为此前数量丰富的北美驯鹿减少了，麝牛数量增加。促进食草动物多样性的努力，如重新造林，或有助于减轻气候变暖对苔原多样性的影响。

▲ Abstract：

Biodiversity is declining globally in response to multiple human stressors, including climate forcing. Nonetheless, local diversity trends are inconsistent in some taxa, obscuring contributions of local processes to global patterns. Arctic tundra diversity, including plants, fungi, and lichens, declined during a 15-year experiment that combined warming with exclusion of large herbivores known to influence tundra vegetation composition. Tundra diversity declined regardless of experimental treatment, as background growing season temperatures rose with sea ice loss. However, diversity declined slower with large herbivores than without them. This difference was associated with an increase in effective diversity of large herbivores as formerly abundant caribou declined and muskoxen increased. Efforts that promote herbivore diversity, such as rewilding, may help mitigate impacts of warming on tundra diversity.