On September 4, 2024, the research results of academician Ye Jun and Zhang Chuankun's team: the atomic clock project, once again appeared on the cover of Nature.

2024年9月4日，葉軍院士、張傳坤團隊的研究成果：原子鐘項目，再次登Nature封面。

This article, entitled "Frequency ratio of the 22?? Th nuclear isomeric transition and the ??Sr atomic clock", was published in Nature and was sexted as the cover of that issue.

這篇題為《釷-229m核異構(gòu)躍遷和鍶-87原子鐘的頻率比》的文章，發(fā)表在Nature 上，并被選為當期封面。

It took only 27 days from submission to acceptance of this paper, and it was reported by Nature's nature podcast series, news & views series, news series, editorials series and Science's News series.

這篇論文從投稿到接收僅僅27天，并同時被《Nature》的nature podcast系列、news & views系列、news系列、editorials系列以及《Science》的News系列報道。

The achievement launches a new human endeavor: a new type of clock timer developed by the team based on tiny changes in energy in atomic nuclei - a nuclear clock, may surpass today's most advanced atomic clocks in accuracy and stability, and is less sensitive to interference, which makes scientists excited to use them as detectors of dark matter and other fundamental physics problems, using this discovery to observe whether the laws of physics change over time.

這項成果發(fā)起了一項人類新的努力：團隊開發(fā)的一種基于原子核中能量微小變化的新型時鐘計時器——核鐘，在準確性和穩(wěn)定性方面可能超越當今最先進的原子鐘，且對干擾的敏感度更低，這讓科學家們很高興將它們用作暗物質(zhì)和其他基本物理問題的探測器，利用這一發(fā)現(xiàn)來觀察物理定律是否隨著時間的推移而變化。

This research by Ye Jun's team also marks the beginning of nuclear-based solid-state optical clocks, laying the foundation for the future use of this new type of clock in practical situations.

葉軍團隊的這項研究也標志著核基固態(tài)光學鐘的開端，給這種新型時鐘以后用在實際情況中打下了基礎。

The "Ultimate Timer" is launched for the first time worldwide!

「終極計時器」全球首次啟動！

The technology for measuring time has a long history of innovation: from calculating the phases of the moon to the invention of the pendulum and quartz oscillator.

測量時間的技術經(jīng)歷了悠久的創(chuàng)新歷史：從計算月相到鐘擺和石英振盪器的發(fā)明。

The current global timekeeping standard is an atomic clock based on the microwave frequency transitions of cesium atoms. These precision devices can be precisely synchronized around the world with an accuracy of up to 16 decimal places, enough to support space missions and help people use the global GPS positioning system to achieve navigation with an accuracy of less than 1 meter.

目前全球計時標準是一種基于銫原子微波頻率躍遷的原子鐘，這些精密設備可以在全球范圍內(nèi)精確同步，精度可達小數(shù)點后16位數(shù)，足以支持太空任務，并幫助人們使用全球GPS定位系統(tǒng)實現(xiàn)精度在1米以內(nèi)的導航。

A different type of atomic clock uses transitions that emit light in the optical (rather than microwave) range. By precisely amplifying specific energy transitions in atomic nuclei, researchers are closer than ever to building a new type of timekeeper: a nuclear clock.

另一種不同類型的原子鐘使用在光學（而不是微波）范圍內(nèi)發(fā)射光的躍遷。 通過精確放大原子核中的特定能量轉(zhuǎn)變，研究人員比以往任何時候都更接近于構(gòu)建一種新型計時器：核鐘。

Until now, the most accurate clocks were optical clocks made of strontium atoms, which are largely unaffected by external disturbances and are about 100 times more accurate than standard cesium clocks.

在此之前，精度最高的鐘是由鍶原子構(gòu)成的光鐘，基本不受外界擾動的影響。 它比標準銫鐘的精度高出約100倍。

Specifically, the team used a vacuum ultraviolet (VUV) frequency comb to directly excite narrow thorium-229 (22?Th) nuclear clock transitions in a solid-state CaF? host material and determine the absolute transition frequencies.

具體而言，團隊成員使用真空紫外（VUV）頻率梳直接激發(fā)固態(tài) CaF? 主體材料中的窄釷-229（22?Th）核鐘躍遷，并確定絕對躍遷頻率。

They stabilized the fundamental frequency comb to a strontium-87 (??Sr) clock at JILA and coherently upconverted the fundamental frequency to its seventh harmonic in the VUV range by using a femtosecond enhancement cavity.

他們將基帶梳穩(wěn)定至JILA的鍶-87（??Sr）時鐘，并通過使用飛秒增強腔將基頻相干上變頻到VUV范圍內(nèi)的第七諧波。
原創(chuàng)翻譯：龍騰網(wǎng) http://www.top-shui.cn 轉(zhuǎn)載請注明出處


This VUV frequency comb established a frequency lix between the energy levels of the nucleus and the energy levels of the electrons, allowing them to directly measure the ratio of the frequency of the thorium-229 nuclear clock transition to that of the strontium-87 atomic clock. The results showed that the thorium-229 nuclear transition frequency is 2,020,407,384.335(2) kHz, and the ratio to the frequency of the strontium-87 atomic clock is 4.707072615078(5).

這種VUV頻率梳在原子核能級與電子能級之間建立了頻率聯(lián)系，使他們能夠直接測量釷-229核鐘躍遷和鍶-87原子鐘的頻率比。 結(jié)果顯示，釷-229的核躍遷頻率為2,020,407,384.335（2） kHz，并且與鍶-87原子鐘的頻率比為4.707072615078（5）。

This result greatly advances the research on thorium-229 nuclear clocks, improving the measurement accuracy by six orders of magnitude compared to previous measurements. They precisely measured nuclear quadrupole splitting and extracted the intrinsic properties of the isomers.

這一結(jié)果極大推進了釷-229核時鐘的研究，相比以往的測量精度提高了六個數(shù)量級。 他們精確測量了核四極劈裂并提取異構(gòu)體的內(nèi)稟性質(zhì)。

The authors also precisely measured the nuclear quadrupole splitting and extracted the intrinsic properties of the isomers. These results mark the beginning of nuclear-based solid-state optical clocks. This work represents a fusion of precision metrology, ultrafast strong-field physics, nuclear physics, and fundamental physics.

作者還精確測量核四極分裂并提取異構(gòu)體的內(nèi)在特性，這些結(jié)果標志著基于核的固態(tài)光學鐘的開始，這項工作代表了精密計量學、超快強場物理、核物理和基礎物理的融合。

Once operational, the nuclear clock will be able to reveal one of the secrets of the universe: whether the nuclear and electromagnetic forces are always constant, or whether some as-yet-unidentified mechanism causes them to drift slowly over time.

一旦核鐘投入使用，它將能夠揭示宇宙的一個秘密：核力與電磁力是否總是恒定的，抑或某種尚未明確的機制令它們隨時間緩慢漂移。

However, nuclear clocks are difficult to make, and it took scientists nearly 50 years to get close to a working model.

但是，核鐘很難制造，科學家花了將近50年的時間才接近工作模型。

Early measurements suggest that the energy required is 3.5 eV, which means that the transition could be driven by conventional lasers.

早期測量數(shù)據(jù)表明，所需能量為3.5 eV，這意味著這種躍遷可以通過常規(guī)激光器來驅(qū)動。

However, subsequent measurements overturned this result, indicating that the actual transition energy is closer to 7.8 eV, which is in the VUV spectrum and may trigger the atoms to release electrons rather than radiate - a process that is faster and less desirable here.

然而，后續(xù)的測量推翻了這一結(jié)果，表明實際的躍遷能量接近7.8 eV，這一能量位于VUV頻譜范圍內(nèi)，并且可能會觸發(fā)原子釋放電子而不是輻射——電子釋放的過程更加快速，并且在這里是不希望發(fā)生的。
原創(chuàng)翻譯：龍騰網(wǎng) http://www.top-shui.cn 轉(zhuǎn)載請注明出處


Furthermore, achieving these energies with lasers is also extremely challenging.

此外，利用激光器達到這樣的能量同樣極具挑戰(zhàn)性。
原創(chuàng)翻譯：龍騰網(wǎng) http://www.top-shui.cn 轉(zhuǎn)載請注明出處


For most atoms, a huge amount of energy is required to lift the nucleus out of its lowest energy state, far beyond what can be achieved using precise, stable probing lasers.

對于大多數(shù)原子來說，需要大量的能量才能將原子核從其最低能量狀態(tài)中抬離，這遠遠超出了使用精確、穩(wěn)定的探測激光器所能達到的效果。

The researchers used a laser device called a frequency comb to detect thorium-229 nuclei embedded in the crystal.

研究人員使用一種稱為頻率梳的激光設備探測了嵌入晶體中的釷-229 原子核

Physicists proposed a thorium-based clock in 2003. But theoretical models of atomic nuclei couldn't predict the energy of this transition with the necessary accuracy, so finding it meant searching through a huge number of possible values.

物理學家在2003年提出了一種基于釷的時鐘。 但是原子核的理論模型無法以必要的精度預測這種躍遷的能量，因此找到這個躍遷意味著要搜索大量可能的值。

Furthermore, thorium-229 decays slowly from its first energy state. Thus, with a half-life of about 30 minutes, the probability of observing one decay per second is low.

此外，釷-229從其第一個能態(tài)緩慢衰變。 因此，半衰期約為30分鐘，觀察到每秒衰變的概率很低。

But scientists' exploration has not stopped. In 2023, rare isotope experts at CERN, the European particle physics laboratory near Geneva, Switzerland, produced thorium-229 using an innovative method and observed low-energy transitions for the first time.

但科學家的探索并不曾止步。 2023年，瑞士日內(nèi)瓦附近的歐洲粒子物理實驗室CERN的稀有同位素專家通過使用創(chuàng)新方法制造了釷-229，并首次觀察到了低能躍遷。

The team implanted enough excited thorium-229 ions into calcium fluoride crystals to detect the emitted photons directly using a VUV spectrometer. This research improved the accuracy of the photon energy estimate to 8.3 eV, accelerating the development of lasers capable of stimulating this transition.

該團隊將足夠數(shù)量的激發(fā)態(tài)釷-229離子注入氟化鈣晶體中，以便使用VUV光譜儀直接檢測到發(fā)射的光子。 這項研究提高了光子能量估計的準確性，將其達到8.3 eV，加速了能夠激發(fā)這種躍遷的激光器的開發(fā)。

In parallel, other authors involved in the current work developed a VUV frequency comb that can excite nuclear transitions and simultaneously synchronize them with a nearby optical clock regulated by strontium atoms.

與此同時，參與當前工作的其他作者開發(fā)了一種VUV頻率梳，可以激發(fā)核躍遷，并同時與附近由鍶原子調(diào)節(jié)的光學時鐘同步。
原創(chuàng)翻譯：龍騰網(wǎng) http://www.top-shui.cn 轉(zhuǎn)載請注明出處


Zhang Chuankun et al. brought the Austrian crystal device to the United States, where they made history by driving excitation with a VUV frequency comb.

張傳坤等人將奧地利晶體裝置帶到了美國，在那里他們用VUV頻率梳驅(qū)動激發(fā)，創(chuàng)造了歷史。

Repeated experiments showed that this frequency comb could excite nuclear transitions and read out their frequencies in relation to those of strontium transitions.

通過反復實驗表明，這種頻率梳可以激發(fā)核躍遷，并讀出其頻率與鍶躍遷頻率的關系。

The lifetime of the nuclear excited states they observed was about 10 minutes, meaning that the system could be used to generate a 2 petahertz (1PHz is 101?Hz) clock with an uncertainty in the microhertz range.

他們觀察到的核激發(fā)態(tài)的壽命約為10分鐘，這意味著該系統(tǒng)可用于產(chǎn)生2拍赫茲（1PHz為101?Hz）的時鐘，且不確定性在微赫茲范圍內(nèi)。

Zhang and his colleagues found a total of seven transitions, five of which were expected due to the energy level splitting caused by the interaction between the charge distribution of the atomic nuclei and the strong intrinsic electric field of the crystal.

張傳坤等人總共發(fā)現(xiàn)了七個躍遷，其中五個躍遷是預期的，這是由于原子核的電荷分布與晶體的強固有電場相互作用而產(chǎn)生的能級分裂。

Currently, any hopes for greater precision are complicated by the width of the comb teeth, which are widened by the process by which they are generated. Further improvements are needed to shrink these teeth for metrology purposes, perhaps by transferring existing technology from the optical to the VUV frequency range.

目前，任何更高精確度的希望都因梳齒的寬度而變得復雜，梳齒的寬度因其生成過程而變寬。 出于計量目的，需要進一步改進以縮小這些齒，可能通過將現(xiàn)有技術從光學頻率范圍轉(zhuǎn)移到VUV頻率范圍。

One exciting prospect involves monitoring how the frequency of transitions in nuclear clocks changes over time. This could reveal hypothesized tiny changes in the fine structure constant (which quantifies the strength of electromagnetic interactions between charged particles) and in the coupling between nuclear particles, all of which would inspire the search for new physics.

一個令人興奮的前景涉及監(jiān)測核鐘的躍遷頻率如何隨時間變化。 這可以揭示精細結(jié)構(gòu)常數(shù)（量化帶電粒子之間電磁相互作用的強度）以及核粒子之間耦合的假設微小變化，所有這些都將激發(fā)對新物理學的探索。

Another tantalizing physics application of nuclear clocks is the search for candidate particles for dark matter, the invisible stuff thought to make up 85 percent of the mass of the universe.

核鐘的另一個誘人的物理應用是尋找暗物質(zhì)的候選粒子，這種看不見的物質(zhì)被認為占宇宙質(zhì)量的85%。

Many models propose that ultralight dark matter particles will interact directly with the strong nuclear force, which binds protons and neutrons together in atomic nuclei. If these particles interact with thorium nuclei, they would disrupt the transition frequencies, disrupting the clock in a detectable way. This work has revealed nuclear behavior in unprecedented detail. The JILA measurements provide evidence that nuclei such as thorium expand and contract unexpectedly as they move between excited and ground states.

許多模型提出超輕暗物質(zhì)粒子將與強核力直接相互作用，強核力將原子核中的質(zhì)子和中子結(jié)合在一起。 如果這些粒子與釷原子核相互作用，它們就會擾亂躍遷頻率，從而以可檢測的方式擾亂時鐘。 這項工作已經(jīng)以前所未有的細節(jié)揭示了核行為。 JILA測量提供的證據(jù)表明，釷等原子核在激發(fā)態(tài)和基態(tài)之間移動時會意外地膨脹和收縮。

The astonishing achievement of Zhang and others foreshadows many fascinating future discoveries and caps off three decades of brilliant research.

張傳坤等人的驚人成就預示著許多令人著迷的未來發(fā)現(xiàn)，并為三十年來的精彩研究畫上句號。

Quantum mechanics has become an important frxwork for understanding and explaining the microscopic world, and the revolution in quantum science is changing our world at an astonishing speed. "Clocks" are one of them, and nuclear clocks are opening a new chapter in human quantum technology.

量子力學已成為了解和解釋微觀世界的重要框架，而量子科學的革命正在以驚人的速度改變我們的世界。 「時鐘」就是其中一種， 核鐘正在開啟人類量子科技的新篇章。