编译 | 未玖
Science , 23 APRIL 2021, VOL 372, ISSUE 6540
《科学》 2021年4月23日，第372卷，6540期
物理学 Physics
Josephson junction infrared single-photon detector
约瑟夫森结红外单光子探测器
作者：Evan D. Walsh, Woochan Jung, Gil-Ho Lee, Dmitri K. Efetov, Bae-Ian Wu, K.-F. Huang, et al.
链接：
摘要
约瑟夫森结是用于高灵敏度磁强计和电压放大器的超导器件，也是高性能低温计算机和超导量子计算机的基础。虽然因库珀对断裂产生的准粒子会降低器件性能，但这种现象也为灵敏探测电磁辐射提供了机会。
研究组演示了通过将光子耦合到石墨烯基约瑟夫森结的局域表面等离子体来探测单个近红外光子。利用电流偏置器件的光子诱导开关统计，研究组揭示了吸收光子产生的准粒子在探测机制中的关键作用。
光子灵敏度将为未来的超导计算架构提供高速、低功耗的光互连。
Abstract
Josephson junctions are superconducting devices used as high-sensitivity magnetometers and voltage amplifiers as well as the basis of high-performance cryogenic computers and superconducting quantum computers. Although device performance can be degraded by the generation of quasiparticles formed from broken Cooper pairs, this phenomenon also opens opportunities to sensitively detect electromagnetic radiation. We demonstrate single near-infrared photon detection by coupling photons to the localized surface plasmons of a graphene-based Josephson junction. Using the photon-induced switching statistics of the current-biased device, we reveal the critical role of quasiparticles generated by the absorbed photon in the detection mechanism. The photon sensitivity will enable a high-speed, low-power optical interconnect for future superconducting computing architectures.
Higher-dimensional supersymmetric microlaser arrays
高维超对称微激光阵列
作者：Xingdu Qiao, Bikashkali Midya, Zihe Gao, Zhifeng Zhang, Haoqi Zhao, Tianwei Wu, et al.
链接：
摘要
随着集成光子学元件数量的增加，复杂度的非线性缩放是阻碍大规模锁相激光阵列的主要障碍。
研究组开发了一种高维超对称形式，用于精确模式控制和非线性功率缩放。这种超对称微激光阵列具有所有倏逝波耦合微环激光器的锁相相干性和同步性，可在基本横向超模中集体振荡，从而实现高辐射、小发散和单频激光发射，且能量密度提高两个数量级。
研究组还证明了构造高辐射涡旋激光束的可行性，即充分利用光的空间自由度提高激光器的性能。该研究方法为在经典和量子两种状态下设计大规模集成光子系统提供了一条新途径。
Abstract
The nonlinear scaling of complexity with the increased number of components in integrated photonics is a major obstacle impeding large-scale, phase-locked laser arrays. Here, we develop a higher-dimensional supersymmetry formalism for precise mode control and nonlinear power scaling. Our supersymmetric microlaser arrays feature phase-locked coherence and synchronization of all of the evanescently coupled microring lasers—collectively oscillating in the fundamental transverse supermode—which enables high-radiance, small-pergence, and single-frequency laser emission with a two-orders-of-magnitude enhancement in energy density. We also demonstrate the feasibility of structuring high-radiance vortex laser beams, which enhance the laser performance by taking full advantage of spatial degrees of freedom of light. Our approach provides a route for designing large-scale integrated photonic systems in both classical and quantum regimes.
材料科学 Materials Science
Broadband directional control of thermal emission
热辐射的宽带定向控制
作者：Jin Xu, Jyotirmoy Mandal, Aaswath P. Raman
链接：
摘要
控制远场热辐射的发射方向是一个重大挑战。光子策略使热辐射在窄带宽上具有角度选择性，但热辐射是一种宽带现象。将发射的热辐射限制在宽频带上固定的窄角范围内的能力，是一种重要但欠缺的能力。
研究组引入了能对热发射进行广谱定向控制的梯度e近零（ENZ）材料。他们演示了两个由多种氧化物构成的发射器，在一系列波长范围（10.0到14.3微米，7.7到11.5微米）的p-偏振中，它们具有较高（>0.7，>0.6）的定向发射率（60 至75 ，70 至85 ）。
这种宽带定向发射主要在高发射率方向上，实现了有意义的辐射热传递。解耦对角度和光谱响应的传统限制提高了热伪装、太阳能加热、辐射冷却和废热回收等应用的性能。
Abstract
Controlling the directionality of emitted far-field thermal radiation is a fundamental challenge. Photonic strategies enable angular selectivity of thermal emission over narrow bandwidths, but thermal radiation is a broadband phenomenon. The ability to constrain emitted thermal radiation to fixed narrow angular ranges over broad bandwidths is an important, but lacking, capability. We introduce gradient epsilon-near-zero (ENZ) materials that enable broad-spectrum directional control of thermal emission. We demonstrate two emitters consisting of multiple oxides that exhibit high (>0.7, >0.6) directional emissivity (60 to 75 , 70 to 85 ) in the p-polarization for a range of wavelengths (10.0 to 14.3 micrometers, 7.7 to 11.5 micrometers). This broadband directional emission enables meaningful radiative heat transfer primarily in the high emissivity directions. Decoupling the conventional limitations on angular and spectral response improves performance for applications such as thermal camouflaging, solar heating, radiative cooling, and waste heat recovery.
地球科学 Earth Science
Assessing China’s efforts to pursue the 1.5 C warming limit
评估中国追求1.5 控温极限所付诸的努力
作者：Hongbo Duan, Sheng Zhou, Kejun Jiang, Christoph Bertram, Mathijs Harmsen, Elmar Kriegler, et al.
链接：
摘要
通过进行多模型研究，研究组发现与“无政策”情况相比，1.5 温控目标要求中国将碳排放和能源消耗分别减少90%和39%以上。在实现接近零排放方面，负排放技术发挥着重要作用，到2050年，碳捕获需平均占总减排量的20%。
研究组的多模型比较揭示了各部门在必要减排方面的巨大差异，而一致的是，要求电力部门在2050年前实现完全脱碳。交叉模型平均值表明，考虑到1.5 升温极限，到2050年，中国累计政策成本可能达到国内生产总值的2.8%至5.7%。
Abstract
Given the increasing interest in keeping global warming below 1.5 C, a key question is what this would mean for China’s emission pathway, energy restructuring, and decarbonization. By conducting a multimodel study, we find that the 1.5 C-consistent goal would require China to reduce its carbon emissions and energy consumption by more than 90 and 39%, respectively, compared with the “no policy” case. Negative emission technologies play an important role in achieving near-zero emissions, with captured carbon accounting on average for 20% of the total reductions in 2050. Our multimodel comparisons reveal large differences in necessary emission reductions across sectors, whereas what is consistent is that the power sector is required to achieve full decarbonization by 2050. The cross-model averages indicate that China’s accumulated policy costs may amount to 2.8 to 5.7% of its gross domestic product by 2050, given the 1.5 C warming limit.
Global groundwater wells at risk of running dry
全球地下水井面临干涸风险
作者：Scott Jasechko, Debra Perrone
链接：
摘要
地下水井为数十亿人提供水源，但当地下水位下降时，它们可能会干涸。
研究组分析了全球约3900万口水井的施工记录。结果显示，6%到20%的水井深度不超过地下水位5米，这意味着如果地下水位仅下降几米，数百万口水井将面临干涸的风险。
此外，在一些地下水位显著下降的地方，新井的建设深度并不比老井深，这表明如果地下水水位继续下降，新井和老井一样也有可能干涸。深层含水层的水质差，建设水井成本高昂，这限制了开采深层地下水以防止水井干涸时失去水源的有效性。
Abstract
Groundwater wells supply water to billions of people, but they can run dry when water tables decline. Here, we analyzed construction records for ~39 million globally distributed wells. We show that 6 to 20% of wells are no more than 5 meters deeper than the water table, implying that millions of wells are at risk of running dry if groundwater levels decline by only a few meters. Further, newer wells are not being constructed deeper than older wells in some of the places experiencing significant groundwater level declines, suggesting that newer wells are at least as likely to run dry as older wells if groundwater levels continue to decline. Poor water quality in deep aquifers and the high costs of well construction limit the effectiveness of tapping deep groundwater to stave off the loss of access to water as wells run dry.
公共卫生 Public Health
Epidemiological and evolutionary considerations of SARS-CoV-2 vaccine dosing regimes
新冠疫苗给药策略的流行病学和进化研究
作者：Chadi M. Saad-Roy, Sinead E. Morris, C. Jessica E. Metcalf, Michael J. Mina, Rachel E. Baker, Jeremy Farrar, et al.
链接：
摘要
鉴于疫苗剂量短缺和后勤挑战，各国正在提出多种部署战略，以提高人群对SARS-CoV-2的免疫水平。
目前有两个关键问题：通过部分免疫个体累积，第二剂疫苗的注射时间将如何影响感染动力学，以及如何影响病毒免疫逃逸进化的预期。与自然免疫和双剂量免疫相比，两者都取决于单剂量免疫所引发免疫应答的稳健性。
基于现有的免疫-流行病学模型，研究组发现在短期内，集中进行单剂量接种通常可减少感染，但长期结果取决于这种相对免疫的稳健性。之后他们探讨了三种选择方案，发现在部分群体免疫的特定条件下，一剂策略可能会增加抗原进化的潜力。
研究组强调，迫切需要在一剂疫苗接种后检测病毒载量和量化免疫反应，并在全球范围内加强疫苗接种工作。
Abstract
Given vaccine dose shortages and logistical challenges, various deployment strategies are being proposed to increase population immunity levels to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Two critical issues arise: How timing of delivery of the second dose will affect infection dynamics and how it will affect prospects for the evolution of viral immune escape via a buildup of partially immune inpiduals. Both hinge on the robustness of the immune response elicited by a single dose as compared with natural and two-dose immunity. Building on an existing immuno-epidemiological model, we find that in the short term, focusing on one dose generally decreases infections, but that longer-term outcomes depend on this relative immune robustness. We then explore three scenarios of selection and find that a one-dose policy may increase the potential for antigenic evolution under certain conditions of partial population immunity. We highlight the critical need to test viral loads and quantify immune responses after one vaccine dose and to ramp up vaccination efforts globally.
新冠肺炎确诊病例持续增加，却丝毫看不到疫苗成功。并不是人们不想加快疫苗研制的步伐，而是研制疫苗过程中需要克服很多难关，那么新冠肺炎疫苗研制成功和问世需要克服哪些难关？
虽然很多国家都在研制新冠疫苗，但每个国家的角度不同。就像我国已经开展了好多期实验，主要为了证实疫苗具有安全性，能够成功诱导体内产生免疫应答。
牛津大学也发布了相关论文，该款疫苗已经能够成功引起体内免疫应答，且不会造成太大的副作用，目前疫苗已经得到了临床验证，正在进行大规模的临床实验。
总关这些国家对疫苗的研究成果，我们可以发现新冠疫苗研制的时间不会太长，或许年底就能成功研制出新冠肺炎的特效药，不过我们还是要注意肺炎疫苗研制过程中需要克服的难题。
首先我们要明确一个问题，什么是病毒？病毒能够通过自我复制大量繁殖。研制过程中要克服的第一个难题，就是找出病毒的DNA链。生物学家和科学家通过研制新冠病毒的DNA量来完美复制病毒，这是新冠病毒疫苗需要克服的第一个难关，如何才能找到DNA链？如何才能进行自我复制？
其次，新冠肺炎对于哪些药物有抵抗性？哪些药物又能治疗新冠肺炎？找到DNA链研究出病毒的自我复制模式，寻找能够治疗该病毒的特效药。不是每一个过程都是那么简单，世界上存在着各种各样的抗生素，从数以万计的抗生素中找到能够抵御新冠病毒的抗生素难上加难。
最后要克服的难题是该疫苗是否对人体造成副作用？一款疫苗的成功，需要人们尝试大量的实验，其中就包括很多期的人体实验。科学家要通过注射到人体中的疫苗产生的作用来判断疫苗能否获得上市资格。如果这款疫苗对人体造成极大的副作用，那么该款疫苗的上市夭折了。
