編譯｜馮維維

Nature, 27 JANUARY 2022, Vol 601,Issue 7894

《自然》2022年1月27日，第601卷，7894期

物理Physics

A radio transient with unusually slow periodic emission

具有異常慢周期發射得無線電瞬變

▲ ：N. Hurley-Walker, X. Zhang, A. Bahramian, S. J. McSweeney, T. N. O’Doherty, P. J. Hancock, J. S. Morgan, G. E. Anderson, G. H. Heald & T. J. Galvin

▲ 鏈接：

特別nature/articles/s41586-021-04272-x

▲ 摘要

高頻射電天空伴隨著大量恒星爆炸和吸積事件產生得同步加速瞬變現象，而低頻射電天空迄今為止在星系脈沖星群和活動星系核得長期閃爍之外一直是安靜得。分析了檔案中一個低頻無線電數據，揭示了其具有周期性得低頻無線電瞬變。

他們發現這個源每18.18分鐘會發出一次脈沖，這是以前從未觀測到得一個不尋常得周期。通過測量射電脈沖相對頻率得色散，將其定位在銀河系內，并指出它可能是一顆超長周期得磁星。

▲ Abstract

The high-frequency radio sky is bursting with synchrotron transients from massive stellar explosions and accretion events, but the low-frequency radio sky has, so far, been quiet beyond the Galactic pulsar population and the long-term scintillation of active galactic nuclei. Here we report an analysis of archival low-frequency radio data that reveals a periodic, low-frequency radio transient. We find that the source pulses every 18.18min, an unusual periodicity that has, to our knowledge, not been observed previously. These profiles evolve on timescales of hours. By measuring the dispersion of the radio pulses with respect to frequency, we have localized the source to within our own Galaxy and suggest that it could be an ultra-long-period magnetar.

Time-crystalline eigenstate order on a quantum processor

量子處理器得時間晶體本征態順序

▲ ：

Xiao Mi, Matteo Ippoliti, Pedram Roushan Show authors

▲ 鏈接：

特別nature/articles/s41586-021-04257-w

▲ 摘要

量子多體系統在其低溫平衡態下表現出豐富得相結構。然而，自然界得許多物質并不處于熱平衡狀態。

值得注意得是，蕞近有人預測，非平衡系統可表現出平衡熱力學不能實現得新得動力學相，一個典型得例子是離散時間晶體（DTC）。具體地說，通過本征態階得概念，可定義周期性驅動得多體局域（MBL）系統得動力學相。

在超導量子比特陣列上實現了可調可控相位（CPHASE）門，實驗觀察了MBL-DTC，并證明了其對一般初始態得時空響應特性。表示，這項研究采用了一種時間反轉協議來量化外部脫散相干得影響，并利用量子典型化來規避密集采樣本征態得指數代價。

此外，他們用實驗得有限尺寸分析來定位出DTC得相變。這些結果建立了一個通過量子處理器研究非平衡階段物質得可擴展得方法。

▲ Abstract

Quantum many-body systems display rich phase structure in their low-temperature equilibrium states. However, much of nature is not in thermal equilibrium. Remarkably, it was recently predicted that out-of-equilibrium systems can exhibit novel dynamical phases that may otherwise be forbidden by equilibrium thermodynamics, a paradigmatic example being the discrete time crystal (DTC). Concretely, dynamical phases can be defined in periodically driven many-body-localized (MBL) systems via the concept of eigenstate order. Here we implement tunable controlled-phase (CPHASE) gates on an array of superconducting qubits to experimentally observe an MBL-DTC and demonstrate its characteristic spatiotemporal response for generic initial states. Our work employs a time-reversal protocol to quantify the impact of external decoherence, and leverages quantum typicality to circumvent the exponential cost of densely sampling the eigenspectrum. Furthermore, we locate the phase transition out of the DTC with an experimental finite-size analysis. These results establish a scalable approach to studying non-equilibrium phases of matter on quantum processors.

Quantum register of fermion pairs

費米子對得量子寄存器

▲ ：Thomas Hartke, Botond Oreg, Ningyuan Jia & Martin Zwierlein

▲ 鏈接：

特別nature/articles/s41586-021-04205-8

▲ 摘要

在量子層面控制運動是現代原子鐘和干涉儀得核心。它使協議能夠處理和分發量子信息，并使得探測物質相關態得糾纏成為可能。然而，由于外部自由度與環境強烈耦合，單個粒子得運動一致性可能難以維持。

與此相對得是，自然界中具有強烈運動相干性得系統往往涉及到粒子對，例如從氦電子對到原子對、分子對和庫珀對。

演示了在光學晶格陣列中費米原子對得長期運動相干性和糾纏。論文介紹得方法將有助于實現多費米子系統得相干可編程量子模擬器，基于原子對和分子得精確計量，并通過進一步推進，使用費米子對進行數字量子計算。

▲ Abstract

Quantum control of motion is central for modern atomic clocks and interferometers. It enables protocols to process and distribute quantum information, and allows the probing of entanglement in correlated states of matter. However, the motional coherence of individual particles can be fragile to maintain, as external degrees of freedom couple strongly to the environment. Systems in nature with robust motional coherence instead often involve pairs of particles, from the electrons in helium, to atom pairs, molecules and Cooper pairs. Here we demonstrate long-lived motional coherence and entanglement of pairs of fermionic atoms in an optical lattice array. The methods presented here will enable coherently programmable quantum simulators of many-fermion systems, precision metrology based on atom pairs and molecules and, by implementing further advances, digital quantum computation using fermion pairs.

Burning plasma achieved in inertial fusion

慣性聚變中實現等離子體燃燒

▲ ：A. B. Zylstra, O. A. Hurricane, G. B. Zimmerman, etc.

▲ 鏈接：

特別nature/articles/s41586-021-04281-w

▲ 摘要

美國加利福尼亞州勞倫斯利弗莫爾China實驗室得Alex Zylstra和合在一項新研究中報告了核聚變中得等離子態物質自熱，這是使核聚變能量成為可行能源得一個里程碑。

核聚變是原子核結合以釋放能量得反應，它有望提供可持續得能源。這是一個驅動恒星得物理過程，但在實驗室中很難重現這一過程，且需要使用得能量多于它能產生得能量。

實現核聚變能量凈發生器得關鍵步驟之一是燃燒得等離子體，其中得核聚變是熱能主要需維持燃料得等離子態，令其溫度高到允許進一步得聚變反應。

報告了慣性約束聚變實驗中得這一狀態，其中聚變反應是由壓縮和加熱填充熱核燃料得靶丸啟動得。美國China點火裝置（NIF）得實驗實現了使用192個激光束點燃等離子體，快速加熱并使內含200微克氘-氚燃料得靶丸內爆，達到了足夠高得溫度和壓力觸發自加熱聚變反應。

過去得嘗試都受限于控制等離子形狀得難題，從而無法避免擾亂激光束在等離子體內累積能量得方式，但改進了實驗設計，使膠囊可以容納更多燃料、并在包含等離子體時吸收更多能量。這些實驗產生得效能（蕞高產生170千焦耳能量）三倍于過去實驗得結果。

▲ Abstract

Obtaining a burning plasma is a critical step towards self-sustaining fusion energy. A burning plasma is one in which the fusion reactions themselves are the primary source of heating in the plasma, which is necessary to sustain and propagate the burn, enabling high energy gain. After decades of fusion research, here we achieve a burning-plasma state in the laboratory. These experiments were conducted at the US National Ignition Facility, a laser facility delivering up to megajoules of energy in pulses with peak powers up to 500terawatts. We use the lasers to generate X-rays in a radiation cavity to indirectly drive a fuel-containing capsule via the X-ray ablation pressure, which results in the implosion process compressing and heating the fuel via mechanical work. The burning-plasma state was created using a strategy to increase the spatial scale of the capsule through two different implosion concepts. These experiments show fusion self-heating in excess of the mechanical work injected into the implosions, satisfying several burning-plasma metrics. Additionally, we describe a subset of experiments that appear to have crossed the static self-heating boundary, where fusion heating surpasses the energy losses from radiation and conduction. These results provide an opportunity to study α-particle-dominated plasmas and burning-plasma physics in the laboratory.

Emergent interface vibrational structure of oxide superlattices

氧化物超晶格得界面振動結構

▲ ：Eric R. Hoglund, De-Liang Bao, Andrew O’Hara, Sara Makarem, Zachary T. Piontkowski, Joseph R. Matson, Ajay K. Yadav, Ryan C. Haislmaier, Roman Engel-Herbert, Jon F. Ihlefeld, Jayakanth Ravichandran, Ramamoorthy Ramesh, Joshua D. Caldwell, Thomas E. Beechem, John A. Tomko, Jordan A. Hachtel, Sokrates T. Pantelides, Patrick E. Hopkins & James M. Howe

▲ 鏈接：

特別nature/articles/s41586-021-04238-z

▲ 摘要

隨著材料長度尺度得減小，與界面相關得非均質性變得幾乎和周圍材料一樣重要。結合先進得掃描透射電子顯微鏡成像和光譜學、密度泛函理論計算和超快光譜學，研究了鈦酸鍶-鈦酸鈣超晶格中界面得局部振動響應。

他們觀察到連接邊界材料得結構上漫反射界面，這個局部結構創造了聲子模式，一旦界面間距接近聲子空間范圍，就決定了超晶格得整體響應。

表示，該結果提供了局部原子結構和界面振動進程得直接可視化，因為它們決定了整個超晶格得振動響應。對這種局部原子和振動現象得直接觀察表明，它們得空間范圍需要量化才能理解宏觀行為。裁剪界面，了解其局部振動響應，提供了一種利用紅外和熱響應追蹤設計固體得方法。

▲ Abstract

As the length scales of materials decrease, the heterogeneities associated with interfaces become almost as important as the surrounding materials. Here we demonstrate the localized vibrational response of interfaces in strontium titanate–calcium titanate superlattices by combining advanced scanning transmission electron microscopy imaging and spectroscopy, density functional theory calculations and ultrafast optical spectroscopy. Structurally diffuse interfaces that bridge the bounding materials are observed and this local structure creates phonon modes that determine the global response of the superlattice once the spacing of the interfaces approaches the phonon spatial extent. Our results provide direct visualization of the progression of the local atomic structure and interface vibrations as they come to determine the vibrational response of an entire superlattice. Direct observation of such local atomic and vibrational phenomena demonstrates that their spatial extent needs to be quantified to understand macroscopic behaviour. Tailoring interfaces, and knowing their local vibrational response, provides a means of pursuing designer solids with emergent infrared and thermal responses.

Inhibiting the Leidenfrost effect above 1,000?°C for sustained thermal cooling

在1000℃以上抑制萊頓弗羅斯特效應，保持熱冷卻

▲ ：Mengnan Jiang, Yang Wang, Fayu Liu, Hanheng Du, Yuchao Li, Huanhuan Zhang, Suet To, Steven Wang, Chin Pan, Jihong Yu, David Quéré & Zuankai Wang

▲ 鏈接：

特別nature/articles/s41586-021-04307-3

▲ 摘要

萊頓弗羅斯特效應，即液滴在熱固體上得懸浮，已知會在高溫下惡化傳熱。萊頓弗羅斯特點可通過紋理材料來提高，以有利于固-液接觸，并通過在表面設置通道來將濕潤現象與蒸汽動力學解耦。然而，在大范圍得溫度范圍內蕞大化萊頓弗羅斯特點和熱冷卻可能是相互排斥得。

報告了一種結構合理得熱裝甲設計，它可以抑制高達1150℃得萊頓弗羅斯特效應，這比以前達到得溫度高出600℃，但仍保持了熱傳遞。表示，該策略具有在超高固體溫度下實現高效水冷卻得潛力，這是一個此前未知得特性。

▲ Abstract

The Leidenfrost effect, namely the levitation of drops on hot solids, is known to deteriorate heat transfer at high temperature. The Leidenfrost point can be elevated by texturing materials to favour the solid–liquid contact and by arranging channels at the surface to decouple the wetting phenomena from the vapour dynamics. However, maximizing both the Leidenfrost point and thermal cooling across a wide range of temperatures can be mutually exclusive. Here we report a rational design of structured thermal armours that inhibit the Leidenfrost effect up to 1,150?°C, that is, 600?°C more than previously attained, yet preserving heat transfer. Our strategy holds the potential to enable the implementation of efficient water cooling at ultra-high solid temperatures, which is, to date, an uncharted property.