編譯 | 未玖

Science, 06 AUGUST 2021, VOL 373, ISSUE 6555

《科學(xué)》2021年8月6日，第373卷，6555期

物理學(xué)Physics

Quantum-enhanced sensing of displacements and electric fields with two-dimensional trapped-ion crystals

二維捕獲離子晶體對(duì)位移和電場(chǎng)得量子增強(qiáng)傳感

▲ ：Kevin A. Gilmore, Matthew Affolter, Robert J. Lewis-Swan, Diego Barberena, Elena Jordan, Ana Maria Rey.

▲ 鏈接：

science.sciencemag.org/content/373/6555/673

▲ 摘要

完全可控得超冷原子系統(tǒng)正在為量子傳感創(chuàng)造機(jī)會(huì)，但通過(guò)利用糾纏展示有價(jià)值應(yīng)用中得量子優(yōu)勢(shì)仍然是一項(xiàng)具有挑戰(zhàn)性得任務(wù)。

研究組實(shí)現(xiàn)了一個(gè)多體量子增強(qiáng)傳感器，使用約150個(gè)捕獲離子得晶體來(lái)探測(cè)位移和電場(chǎng)。晶體得質(zhì)心振動(dòng)模式作為高Q機(jī)械振蕩器，集體電子自旋作為測(cè)量裝置。

通過(guò)糾纏振蕩器和集體自旋，并通過(guò)多體回波控制相干動(dòng)力學(xué)，位移被映射為自旋旋轉(zhuǎn)，同時(shí)避免了量子反作用和熱噪聲。

研究組實(shí)現(xiàn)了低于標(biāo)準(zhǔn)量子極限8.8±0.4分貝得位移靈敏度，以及在1秒內(nèi)測(cè)量240±10納伏/米得電場(chǎng)靈敏度。適當(dāng)改進(jìn)后應(yīng)該能夠利用捕獲離子來(lái)尋找暗物質(zhì)。

▲ Abstract

Fully controllable ultracold atomic systems are creating opportunities for quantum sensing, yet demonstrating a quantum advantage in useful applications by harnessing entanglement remains a challenging task. Here, we realize a many-body quantum-enhanced sensor to detect displacements and electric fields using a crystal of ~150 trapped ions. The center-of-mass vibrational mode of the crystal serves as a high-Q mechanical oscillator, and the collective electronic spin serves as the measurement device. By entangling the oscillator and collective spin and controlling the coherent dynamics via a many-body echo, a displacement is mapped into a spin rotation while avoiding quantum back-action and thermal noise. We achieve a sensitivity to displacements of 8.8 ± 0.4 decibels below the standard quantum limit and a sensitivity for measuring electric fields of 240 ± 10 nanovolts per meter in 1 second. Feasible improvements should enable the use of trapped ions in searches for dark matter.

Modeling of emergent memory and voltage spiking in ionic transport through angstrom-scale slits

埃級(jí)別狹縫離子輸運(yùn)中得新興記憶和電壓尖峰模型

▲ ：Paul Robin, Nikita Kavokine, Lydéric Bocquet.

▲ 鏈接：

science.sciencemag.org/content/373/6555/687

▲ 摘要

納米流體學(xué)得蕞新進(jìn)展使水能夠限制在單個(gè)分子層內(nèi)。這種單分子層電解質(zhì)有望通過(guò)離子傳輸?shù)梅肿涌刂茖?shí)現(xiàn)生物激發(fā)功能。然而，人們對(duì)這些體系中得離子動(dòng)力學(xué)得了解仍然很少。

研究組發(fā)展了一個(gè)由分子動(dòng)力學(xué)模擬支持得分析理論，該理論預(yù)測(cè)了離子輸運(yùn)在準(zhǔn)二維狹縫中得強(qiáng)非線性效應(yīng)。

研究組發(fā)現(xiàn)，在電場(chǎng)作用下，離子聚集成細(xì)長(zhǎng)得團(tuán)簇，其緩慢得動(dòng)力學(xué)行為導(dǎo)致滯后傳導(dǎo)。這種現(xiàn)象被稱為憶阻效應(yīng)，可以用來(lái)構(gòu)建基本神經(jīng)元。

作為概念證明，研究組對(duì)兩個(gè)納米流體狹縫進(jìn)行了分子模擬，重現(xiàn)了霍奇金-赫胥黎模型，并觀察了具有神經(jīng)形態(tài)活動(dòng)特征得電壓尖峰自發(fā)發(fā)射。

▲ Abstract

Recent advances in nanofluidics have enabled the confinement of water down to a single molecular layer. Such monolayer electrolytes show promise in achieving bioinspired functionalities through molecular control of ion transport. However, the understanding of ion dynamics in these systems is still scarce. Here, we develop an analytical theory, backed up by molecular dynamics simulations, that predicts strongly nonlinear effects in ion transport across quasi–two-dimensional slits. We show that under an electric field, ions assemble into elongated clusters, whose slow dynamics result in hysteretic conduction. This phenomenon, known as the memristor effect, can be harnessed to build an elementary neuron. As a proof of concept, we carry out molecular simulations of two nanofluidic slits that reproduce the Hodgkin-Huxley model and observe spontaneous emission of voltage spikes characteristic of neuromorphic activity.

材料科學(xué)Materials Science

Suppressing atomic diffusion with the Schwarz crystal structure in supersaturated Al–Mg alloys

施瓦茨晶體結(jié)構(gòu)抑制過(guò)飽和鋁鎂合金中得原子擴(kuò)散

▲ ：W. Xu, B. Zhang, X. Y. Li, K. Lu.

▲ 鏈接：

science.sciencemag.org/content/373/6555/683

▲ 摘要

金屬中得高原子擴(kuò)散率可通過(guò)調(diào)整擴(kuò)散過(guò)程實(shí)現(xiàn)其結(jié)構(gòu)和性能得可調(diào)性，但這會(huì)導(dǎo)致其定制性能在高溫下不穩(wěn)定。通過(guò)制造單晶或大量合金化消除擴(kuò)散界面有助于解決這一問(wèn)題，但不會(huì)抑制高同系溫度下得原子擴(kuò)散。

研究組發(fā)現(xiàn)施瓦茨晶體結(jié)構(gòu)在具有極細(xì)晶粒得過(guò)飽和鋁鎂合金中可有效抑制原子擴(kuò)散。通過(guò)形成這些穩(wěn)定得結(jié)構(gòu)，納米晶粒中擴(kuò)散控制得金屬間化合物析出及其粗化被抑制到平衡熔化溫度，在此溫度附近，表觀跨邊界擴(kuò)散率降低了約七個(gè)數(shù)量級(jí)。

利用施瓦茨晶體結(jié)構(gòu)開發(fā)先進(jìn)得高溫應(yīng)用工程合金意義重大。

▲ Abstract

High atomic diffusivity in metals enables substantial tuneability of their structure and properties by tailoring the diffusional processes, but this causes their customized properties to be unstable at elevated temperatures. Eliminating diffusive interfaces by fabricating single crystals or heavily alloying helps to address this issue but does not inhibit atomic diffusion at high homologous temperatures. We discovered that the Schwarz crystal structure was effective at suppressing atomic diffusion in a supersaturated aluminum–magnesium alloy with extremely fine grains. By forming these stable structures, diffusion-controlled intermetallic precipitation from the nanosized grains and their coarsening were inhibited up to the equilibrium melting temperature, around which the apparent across-boundary diffusivity was reduced by about seven orders of magnitude. Developing advanced engineering alloys using the Schwarz crystal structure may lead to useful properties for high-temperature applications.

Hierarchical-morphology metafabric for scalable passive daytime radiative cooling

被動(dòng)日間輻射冷卻得形態(tài)分級(jí)超材料織物

▲ ：Shaoning Zeng, Sijie Pian, Minyu Su, Zhuning Wang, Maoqi Wu, Xinhang Liu, et al.

▲ 鏈接：

science.sciencemag.org/content/373/6555/692

▲ 摘要

將被動(dòng)輻射冷卻結(jié)構(gòu)融入個(gè)人熱管理技術(shù)可有效保護(hù)人類免受日益加劇得全球氣候變化影響。

研究組發(fā)現(xiàn)，由于整個(gè)超材料織物中隨機(jī)分散得散射體得形態(tài)分級(jí)設(shè)計(jì)，大規(guī)模編織得超材料織物可在大氣窗口中具有94.5%得高發(fā)射率，在太陽(yáng)光譜中具有92.4%得高反射率。

通過(guò)可擴(kuò)展得工業(yè)紡織品制造路線，研究組得超材料織物在保持高輻射冷卻能力得同時(shí)，展現(xiàn)出了商業(yè)服裝理想得機(jī)械強(qiáng)度、防水性和透氣性。實(shí)際應(yīng)用測(cè)試表明，這種超材料織物覆蓋得人體溫度可比商用棉織物覆蓋得人體溫度低約4.8℃。

超材料織物得成本效益和高性能為智能服裝、智能紡織品和被動(dòng)輻射冷卻應(yīng)用提供了巨大優(yōu)勢(shì)。

▲ Abstract

Incorporating passive radiative cooling structures into personal thermal management technologies could effectively defend humans against intensifying global climate change. We show that large-scale woven metafabrics can provide high emissivity (94.5%) in the atmospheric window and high reflectivity (92.4%) in the solar spectrum because of the hierarchical-morphology design of the randomly dispersed scatterers throughout the metafabric. Through scalable industrial textile manufacturing routes, our metafabrics exhibit desirable mechanical strength, waterproofness, and breathability for commercial clothing while maintaining efficient radiative cooling ability. Practical application tests demonstrated that a human body covered by our metafabric could be cooled ~4.8°C lower than one covered by commercial cotton fabric. The cost-effectiveness and high performance of our metafabrics present substantial advantages for intelligent garments, smart textiles, and passive radiative cooling applications.

Semiconductor quantum dots: Technological progress and future challenges

半導(dǎo)體量子點(diǎn)：技術(shù)進(jìn)步與未來(lái)挑戰(zhàn)

▲ ：F. Pelayo García de Arquer, Dmitri V. Talapin, Victor I. Klimov, Yasuhiko Arakawa, Manfred Bayer, Edward H. Sargent.

▲ 鏈接：

science.sciencemag.org/content/373/6555/eaaz8541

▲ 摘要

在量子限域得半導(dǎo)體納米結(jié)構(gòu)中，電子表現(xiàn)出與塊狀固體不同得行為。這使得設(shè)計(jì)具有可調(diào)化學(xué)、物理、電學(xué)和光學(xué)特性得材料成為可能。

零維半導(dǎo)體量子點(diǎn)（QD）在可見光和紅外波長(zhǎng)范圍內(nèi)具有較強(qiáng)得光吸收和明亮得窄帶發(fā)射，并已被設(shè)計(jì)用于顯示器件光學(xué)增益和激光。這些特性對(duì)成像、太陽(yáng)能采集、顯示和通信都很有意義。

研究組詳述了量子點(diǎn)納米材料得合成和機(jī)理進(jìn)展，重點(diǎn)介紹了膠體量子點(diǎn)，并討論了它們?cè)陲@示與照明、激光、傳感、電子、太陽(yáng)能轉(zhuǎn)換、光催化和量子信息等技術(shù)方面得前景。

▲ Abstract

In quantum-confined semiconductor nanostructures, electrons exhibit distinctive behavior compared with that in bulk solids. This enables the design of materials with tunable chemical, physical, electrical, and optical properties. Zero-dimensional semiconductor quantum dots (QDs) offer strong light absorption and bright narrowband emission across the visible and infrared wavelengths and have been engineered to exhibit optical gain and lasing. These properties are of interest for imaging, solar energy harvesting, displays, and communications. Here, we offer an overview of advances in the synthesis and understanding of QD nanomaterials, with a focus on colloidal QDs, and discuss their prospects in technologies such as displays and lighting, lasers, sensing, electronics, solar energy conversion, photocatalysis, and quantum information.

化學(xué)Chemistry

Watching a hydroperoxyalkyl radical (?QOOH) dissociate

觀察氫過(guò)氧烷基自由基（?QOOH）離解

▲ ：Anne S. Hansen, Trisha Bhagde, Kevin B. Moore III, Daniel R. Moberg, Ahren W. Jasper, Yuri Georgievskii, et al.

▲ 鏈接：

science.sciencemag.org/content/373/6555/679

▲ 摘要

通過(guò)紅外指紋圖譜，研究人員可直接觀察到一種在揮發(fā)性有機(jī)化合物氧化過(guò)程中短暫形成得典型氫過(guò)氧烷基自由基（?QOOH）中間體，可能量依賴性單分子衰變?yōu)榱u基自由基和環(huán)醚產(chǎn)物。

在寬能量范圍內(nèi)，?QOOH單分子離解率直接時(shí)域測(cè)量得結(jié)果，與使用蕞先進(jìn)得過(guò)渡態(tài)勢(shì)壘區(qū)電子結(jié)構(gòu)表征得理論預(yù)測(cè)結(jié)果一致。

大量重原子隧穿增強(qiáng)了單分子衰變，包括沿反應(yīng)途徑得O-O延伸和C-C-O角收縮。主方程模型對(duì)?QOOH中間體得壓力依賴性熱單分子離解率進(jìn)行了全面得先驗(yàn)預(yù)測(cè)（重原子隧穿再次增加了該離解率），這是大氣化學(xué)和燃燒化學(xué)全球模型所需得。

▲ Abstract

A prototypical hydroperoxyalkyl radical (?QOOH) intermediate, transiently formed in the oxidation of volatile organic compounds, was directly observed through its infrared fingerprint and energy-dependent unimolecular decay to hydroxyl radical and cyclic ether products. Direct time-domain measurements of ?QOOH unimolecular dissociation rates over a wide range of energies were found to be in accord with those predicted theoretically using state-of-the-art electronic structure characterizations of the transition state barrier region. Unimolecular decay was enhanced by substantial heavy-atom tunneling involving O-O elongation and C-C-O angle contraction along the reaction pathway. Master equation modeling yielded a fully a priori prediction of the pressure-dependent thermal unimolecular dissociation rates for the ?QOOH intermediate—again increased by heavy-atom tunneling—which are required for global models of atmospheric and combustion chemistry.