《科学》(20190524出版)一周论文导读

《科学》(20190524出版)一周论文导读
2019年05月26日 20:27 科学网

, 24 May 2019, Vol. 364, No. 6442

《科学》2019年5月24日,第6442期364卷

物理学Physics

Strongly correlated quantum walks with a 12-qubit superconducting processor

超导量子计算在量子随机行走研究中获重要进展

▲ 作者:Zhiguang Yan、Yu-Ran Zhang、Ming Gong、Jian-Wei Pan,et al

▲ 链接:

https://science.sciencemag.org/content/364/6441/eaau0159

▲ 摘要:

量子随机行走是经典随机行走在量子力学中的拓展,区别于经典随机行走,量子随机行走利用量子叠加态的特性,粒子在格点中游走特性需要用量子力学的波函数统计规律来诠释。量子随机游走本身可以模拟多体物理体系的量子行为,并且理论上最终可用于通用量子计算。

研究人员通过设计和加工了高品质的12比特一维链超导比特处理器,成功实现了12个超导量子比特的多体真纠缠态“簇态”的制备。在成功实现12个高质量量子比特计算系统基础上,本研究在世界上首次尝试在固态量子计算系统中实验演示强关联纠缠体系的量子随机行走。研究组详细研究了单粒子及双粒子激发下的量子行走行为,观察到量子行走过程中量子纠缠的传播及演化,并成功观察到了双光子的费米子化行为。

▲ Abstract

Quantum walks are the quantum analogs of classical random walks, which allow for the simulation of large-scale quantum many-body systems and the realization of universal quantum computation without time-dependent control. We experimentally demonstrate quantum walks of one and two strongly correlated microwave photons in a one-dimensional array of 12 superconducting qubits with short-range interactions. First, in one-photon quantum walks, we observed the propagation of the density and correlation of the quasiparticle excitation of the superconducting qubit and quantum entanglement between qubit pairs. Second, when implementing two-photon quantum walks by exciting two superconducting qubits, we observed the fermionization of strongly interacting photons from the measured time-dependent long-range anticorrelations, representing the antibunching of photons with attractive interactions. The demonstration of quantum walks on a quantum processor, using superconducting qubits as artificial atoms and tomographic readout, paves the way to quantum simulation of many-body phenomena and universal quantum computation.

Electrified methane reforming: A compact approach to greener industrial hydrogen production

一种更环保的工业氢生产法

▲ 作者:Sebastian T. Wismann、Jakob S. Engbæk、Søren B. Vendelbo,et al

▲ 链接:

https://science.sciencemag.org/content/364/6442/756

▲ 摘要:

通过用极高温度和蒸汽,蒸汽甲烷重整可将甲烷转变为二氧化碳和氢气。然而,这种广泛使用的方法也会留下明显的二氧化碳足迹;这不仅因为该温室气体会作为反应的副产物而产生,而且驱动反应所需的热量来自化石燃料燃烧。

本文报告了一种更环保的工业制氢法。研究人员提出一种电力驱动版本的甲烷重整,它用的是AC电流和直接电阻加热反应器。与常规方法不同,该通电过程可对反应器均匀供热,令甲烷得到最大限度转化但同时限制了有害含碳副产物的形成。更重要的是,能基于集成加热设计出格外紧凑的反应器,它可能比常规的蒸汽甲烷重整平台小100倍。

▲ Abstract

Electrification of conventionally fired chemical reactors has the potential to reduce CO2 emissions and provide flexible and compact heat generation. Here, we describe a disruptive approach to a fundamental process by integrating an electrically heated catalytic structure directly into a steam-methane–reforming (SMR) reactor for hydrogen production. Intimate contact between the electric heat source and the reaction site drives the reaction close to thermal equilibrium, increases catalyst utilization, and limits unwanted byproduct formation. The integrated design with small characteristic length scales allows compact reactor designs, potentially 100 times smaller than current reformer platforms. Electrification of SMR offers a strong platform for new reactor design, scale, and implementation opportunities. Implemented on a global scale, this could correspond to a reduction of nearly 1% of all CO2 emissions.

生物化学Biochemistry

Role of AcrAB-TolC multidrug efflux pump in drug-resistance acquisition by plasmid transfer

AcrAB-TolC多药外排泵在细菌耐药性的作用

▲ 作者:Sophie Nolivos、Julien Cayron、Annick Dedieu,et al

▲ 链接:

https://science.sciencemag.org/content/364/6442/778

▲ 摘要:

细菌可从其他细菌那里通过诸如细菌接合等基因水平转移机制来接受小片段的DNA(质粒),这种过程常常能赋予接受方细胞基因优势,其中包括对抗生素的耐药性。在耐药菌中已经发现了大量的接合质粒,它们携带着一或多种对大多数临床所用抗生素药物的耐药基因。尽管细菌结合是耐药性传播的主要方法,但人们对该过程的诸多方面仍不清楚。

本研究对一个携带四环素耐药基因质粒的转移进行了追踪,该质粒从一个耐药的大肠杆菌捐体细菌转移到另一个接受体细菌,后者最初对该抗生素是敏感的。在质粒编码基因转移后不久,TetA在接受方细菌中被快速生成(TetA是一种介导四环素耐药性的蛋白)。而且,先前对抗生素敏感的细菌仍然能产生TetA耐受因子并通过质粒交换而获得对四环素的耐药性。这些结果表明,这种能力源自细菌的AcrAB-TolC多药外排泵,后者能减轻四环素的表达阻断作用,并同时令抗生素耐药性得到确立。

▲ Abstract

Drug-resistance dissemination by horizontal gene transfer remains poorly understood at the cellular scale. Using live-cell microscopy, we reveal the dynamics of resistance acquisition by transfer of the Escherichia coli fertility factor–conjugation plasmid encoding the tetracycline-efflux pump TetA. The entry of the single-stranded DNA plasmid into the recipient cell is rapidly followed by complementary-strand synthesis, plasmid-gene expression, and production of TetA. In the presence of translation-inhibiting antibiotics, resistance acquisition depends on the AcrAB-TolC multidrug efflux pump, because it reduces tetracycline concentrations in the cell. Protein synthesis can thus persist and TetA expression can be initiated immediately after plasmid acquisition. AcrAB-TolC efflux activity can also preserve resistance acquisition by plasmid transfer in the presence of antibiotics with other modes of action.

材料学Material

A radiative cooling structural material

一种辐射冷却结构材料

▲ 作者:Tian Li、Yao Zhai、Shuaiming He、Wentao Gan、Zhiyuan Wei,et al

▲ 链接:

https://science.sciencemag.org/content/364/6442/760

▲ 摘要:

被动辐射冷却材料可通过偏转入射日光照射及消散热能来冷却建筑物,而这一过程无需耗能。尽管有几种在建筑物内实现被动辐射冷却的方法已得到实验证明,但仍无法推广。

这里,研究人员增强了已经广泛使用的、可持续性建筑材料的特质,令其具有力学和辐射冷却属性。研究人员表示,完全的去木质化和密实化过程不仅令木头强度显著增加,而且还会导致纤维素纳米纤维的部分对齐排列,赋予该能冷却的木材具有高度反射阳光和高红外辐射性的表面。测试显示,它能日夜不断地冷却至低于环境的温度。这可为削减高达50%的与建筑物冷却相关的能源成本提供可持续性的途径。

▲ Abstract

Reducing human reliance on energy-inefficient cooling methods such as air conditioning would have a large impact on the global energy landscape. By a process of complete delignification and densification of wood, we developed a structural material with a mechanical strength of 404.3 megapascals, more than eight times that of natural wood. The cellulose nanofibers in our engineered material backscatter solar radiation and emit strongly in mid-infrared wavelengths, resulting in continuous subambient cooling during both day and night. We model the potential impact of our cooling wood and find energy savings between 20 and 60%, which is most pronounced in hot and dry climates.

地球物理学Geophysics

Searching for hidden earthquakes in Southern California

在南加州寻找隐藏的地震

▲ 作者:Zachary E. Ross、Daniel T. Trugman、Egill Hauksson、Peter M. Shearer

▲ 链接:

https://science.sciencemag.org/content/364/6442/767

▲ 摘要:

在地震规模与频率间存在着众所周知的经验关系,即地震级数下降1个单位,地震发生频率会增加近10倍。然而,编目低级数地震颇为困难,因为其地震信号和近乎同时发生的交叠地震能量常常与背景噪音难以区分。

为了克服低信噪比的问题,本研究采用了一种被称为“模板匹配”的算法搜寻南加州的隐匿地震,因为该算法能从连续地震数据流中梳理出隐微的地震波形。研究人员给出了南加州迄今为止最全面的地震统计数据。数据显示,在2008年至2017年间南加州出现超过180万次地震,比原先南加州地震网(SCSN)记载的地震次数多了10倍,这里每天会发生约495次地震,大约每174秒发生1次。

▲ Abstract

Earthquakes follow a well-known power-law size relation, with smaller events occurring much more often than larger events. Earthquake catalogs are thus dominated by small earthquakes yet are still missing a much larger number of even smaller events because of signal fidelity issues. To overcome these limitations, we applied a template-matching detection technique to the entire waveform archive of the regional seismic network in Southern California. This effort resulted in a catalog with 1.81 million earthquakes, a 10-fold increase, which provides important insights into the geometry of fault zones at depth, foreshock behavior and nucleation processes, and earthquake-triggering mechanisms. The rich detail resolved in this type of catalog will facilitate the next generation of analyses of earthquakes and faults.

Shifting habitat mosaics and fish production across river basins

跨流域栖息地变化和鱼类生产

▲ 作者:Sean R. Brennan、Daniel E. Schindler、Timothy J. Cline,et al

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