编译 | 李言

Nature, 16 May 2024, Volume 629 Issue 8012

《自然》2024年5月16日，第629卷，8012期

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量子物理学Quantum Physics

Probing entanglement in a 2D hard-core Bose–Hubbard lattice

二维硬核玻色—哈伯德晶格中的纠缠探测

▲ 作者：Amir H. Karamlou, Ilan T. Rosen et al.

▲ 链接：

https://www.nature.com/articles/s41586-024-07325-z

▲ 摘要：

在此，我们使用可控的4×4超导量子比特阵列来模拟二维硬核玻色—哈伯德晶格。我们通过同时驱动所有晶格格位产生叠加态，并在其多体能谱中提取相关长度和纠缠熵。我们观察到光谱中心状态的体积律纠缠缩放，以及在其边缘附近开始的面积定律缩放的交叉。

▲ Abstract：

Here we use a controllable 4 × 4 array of superconducting qubits to emulate a 2D hard-core Bose–Hubbard (HCBH) lattice. We generate superposition states by simultaneously driving all lattice sites and extract correlation lengths and entanglement entropy across its many-body energy spectrum. We observe volume-law entanglement scaling for states at the centre of the spectrum and a crossover to the onset of area-law scaling near its edges.

Fusion of deterministically generated photonic graph states

确定性生成光子图态的融合

▲ 作者：Philip Thomas, Leonardo Ruscio, Olivier Morin & Gerhard Rempe

▲ 链接：

https://www.nature.com/articles/s41586-024-07357-5

▲ 摘要：

尽管如贝尔态或线性簇态这样的小型图态已经能够通过光子产生，但为了满足日益增长的量子计算和量子网络应用需求，需要可编程的方法将这些小规模的纠缠态融合成更强大的状态。

在此，我们通过使用包含两个单独可寻址原子的光学谐振器来实现这一目标。环形和树形图态最多有8个量子比特，其名称反映纠缠拓扑，有效地融合了单个原子的光子态。

核聚变过程本身在两个原子之间使用一个腔辅助门。我们的技术原则上可以扩展到更大数量的量子比特，并且成为未来量子互联网中无记忆量子中继器的决定性一步。

▲ Abstract：

Small graph states such as Bell or linear cluster states have been produced with photons, but the proposed quantum-computing and quantum-networking applications require fusion of such states into larger and more powerful states in a programmable fashion. Here we achieve this goal by using an optical resonator containing two individually addressable atoms. Ring and tree graph states with up to eight qubits, with the names reflecting the entanglement topology, are efficiently fused from the photonic states emitted by the individual atoms. The fusion process itself uses a cavity-assisted gate between the two atoms. Our technique is, in principle, scalable to even larger numbers of qubits and is the decisive step towards, for instance, a memory-less quantum repeater in a future quantum internet.

建筑学uArchitecture

Arresting failure propagation in buildings through collapse isolation

通过隔离崩塌阻止建筑物内破坏蔓延

▲ 作者：Nirvan Makoond, Andri Setiawan, Manuel Buitrago & Jose M. Adam

▲ 链接：

https://www.nature.com/articles/s41586-024-07268-5

▲ 摘要：

在此，我们提出了一种原始的设计方法来阻止主要初始故障后的崩塌蔓延。当倒塌开始时，该方法确保在整体稳定的最关键组成部分失效之前，特定要素会失效。这样，结构体系就分裂成不同的部分，并在其蔓延不可避免时隔离崩塌。

通过对一个专门建造的全尺寸建筑物进行实验测试，我们证明了该方法的有效性。我们还证明，如果按照当前方式的建议增加连接性，那么大的初始故障将导致测试建筑的完全崩塌。我们提出的方法可以为更具弹性的建筑建立最后一道防线。

▲ Abstract：

Here we present an original design approach to arrest collapse propagation after major initial failures. When a collapse initiates, the approach ensures that specific elements fail before the failure of the most critical components for global stability. The structural system thus separates into different parts and isolates collapse when its propagation would otherwise be inevitable. The effectiveness of the approach is proved through unique experimental tests on a purposely built full-scale building. We also demonstrate that large initial failures would lead to total collapse of the test building if increased connectivity was implemented as recommended by present guidelines. Our proposed approach enables incorporating a last line of defence for more resilient buildings.

能源科学Energy Science

A high-density and high-confinement tokamak plasma regime for fusion energy

可用于聚变能的高密度高约束托卡马克等离子体

▲ 作者：S. Ding, A. M. Garofalo et al.

▲ 链接：

https://www.nature.com/articles/s41586-024-07313-3

▲ 摘要：

在此，我们报告了稳定的托卡马克等离子体的演示，其线平均密度比格林沃尔德密度高约20%，能量约束质量比标准高约束模式提升约50%，这是通过利用高极向—β情景下高密度梯度对湍流输运的增强抑制实现的。

此外，我们的实验结果显示了极低边缘瞬态扰动，与高归一化密度和约束核心的积分。我们报告的运行机制支持世界上许多聚变反应堆设计的关键要求，并为经济可行的聚变能源开辟了潜在的途径。

▲ Abstract：

Here we report the demonstration of stable tokamak plasmas with a line-averaged density approximately 20% above the Greenwald density and an energy confinement quality of approximately 50% better than the standard high-confinement mode, which was realized by taking advantage of the enhanced suppression of turbulent transport granted by high density-gradients in the high-poloidal-beta scenario. Furthermore, our experimental results show an integration of very low edge transient perturbations with the high normalized density and confinement core. The operating regime we report supports some critical requirements in many fusion reactor designs all over the world and opens a potential avenue to an operating point for producing economically attractive fusion energy.

地球科学Earth science

One-third of Southern Ocean productivity is supported by dust deposition

沙尘沉积支撑了南大洋三分之一的生产力

▲ 作者：Jakob Weis, Zanna Chase et al.

▲ 链接：

https://www.nature.com/articles/s41586-024-07366-4

▲ 摘要：

在此，我们结合了11年来自主生物地球化学的海洋剖面浮标的硝酸盐观测数据和南半球的尘埃模拟，以经验推导出铁有限的南大洋中尘埃—铁沉积与年净群落产量（ANCP）之间的关系。利用这一信息，我们确定了目前和末次盛冰期（LGM）期间南大洋中上层常年无冰地区对尘埃—铁的生物响应。

我们估计尘埃—铁现在支持这南大洋年净群落产量的33%±15%。在末次盛冰期期间，当沙尘沉降比今天高5—40倍时，沙尘对南大洋年净群落产量的贡献要大得多，估计为64%±13%。

▲ Abstract：

Here we combined 11 years of nitrate observations from autonomous biogeochemical ocean profiling floats with a Southern Hemisphere dust simulation to empirically derive the relationship between dust-iron deposition and annual net community production (ANCP) in the iron-limited Southern Ocean. Using this relationship, we determined the biological response to dust-iron in the pelagic perennially ice-free Southern Ocean at present and during the last glacial maximum (LGM). We estimate that dust-iron now supports 33% ± 15% of Southern Ocean ANCP. During the LGM, when dust deposition was 5–40-fold higher than today, the contribution of dust to Southern Ocean ANCP was much greater, estimated at 64% ± 13%.

生物学Biology

Sleep pressure modulates single-neuron synapse number in zebrafish

睡眠压力调节斑马鱼单神经元突触数

▲ 作者：Anya Suppermpool, Declan G. Lyons, Elizabeth Broom & Jason Rihel

▲ 链接：

https://www.nature.com/articles/s41586-024-07367-3

▲ 摘要：

在此，通过反复对斑马鱼幼体睡眠—清醒状态下单个神经元上的所有兴奋性突触进行成像，我们发现在清醒期间会获得突触，在睡眠期间以神经元亚型依赖的方式丢失突触。

然而，在长时间清醒后，与高睡眠压力相关的睡眠期间突触损失最大，而在未受干扰的夜晚后半段，突触损失最低。与此相反，在低睡眠压力时期，药物导致的睡眠不足以引发突触丢失，除非腺苷水平被提高，去甲肾上腺素能张力被抑制。

由此我们认为，睡眠依赖的突触损失是由单个神经元水平的睡眠压力调节的，并不是所有的睡眠时期都能达成突触稳态的功能。

▲ Abstract：

Here, by repeatedly imaging all excitatory synapses on single neurons across sleep–wake states of zebrafish larvae, we show that synapses are gained during periods of wake (either spontaneous or forced) and lost during sleep in a neuron-subtype-dependent manner. However, synapse loss is greatest during sleep associated with high sleep pressure after prolonged wakefulness, and lowest in the latter half of an undisrupted night. Conversely, sleep induced pharmacologically during periods of low sleep pressure is insufficient to trigger synapse loss unless adenosine levels are boosted while noradrenergic tone is inhibited. We conclude that sleep-dependent synapse loss is regulated by sleep pressure at the level of the single neuron and that not all sleep periods are equally capable of fulfilling the functions of synaptic homeostasis.