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Vertical angular momentum constraint on lunar formation and orbital history 期刊论文
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2020, 117 (27) : 15460-15464
作者:  Tian, ZhenLiang;  Wisdom, Jack
收藏  |  浏览/下载:8/0  |  提交时间:2020/06/29
moon formation  orbital evolution  angular momentum  
Laser spectroscopy of pionic helium atoms 期刊论文
NATURE, 2020, 581 (7806) : 37-+
作者:  Shang, Jian;  Ye, Gang;  Shi, Ke;  Wan, Yushun;  Luo, Chuming;  Aihara, Hideki;  Geng, Qibin;  Auerbach, Ashley;  Li, Fang
收藏  |  浏览/下载:21/0  |  提交时间:2020/07/03

Charged pions(1) are the lightest and longest-lived mesons. Mesonic atoms are formed when an orbital electron in an atom is replaced by a negatively charged meson. Laser spectroscopy of these atoms should permit the mass and other properties of the meson to be determined with high precision and could place upper limits on exotic forces involving mesons (as has been done in other experiments on antiprotons(2-9)). Determining the mass of the pi(-) meson in particular could help to place direct experimental constraints on the mass of the muon antineutrino(10-13). However, laser excitations of mesonic atoms have not been previously achieved because of the small number of atoms that can be synthesized and their typically short (less than one picosecond) lifetimes against absorption of the mesons into the nuclei(1). Metastable pionic helium (pi He-4(+)) is a hypothetical(14-16) three-body atom composed of a helium-4 nucleus, an electron and a pi(-) occupying a Rydberg state of large principal (n approximate to 16) and orbital angular momentum (l approximate to n - 1) quantum numbers. The pi He-4(+) atom is predicted to have an anomalously long nanosecond-scale lifetime, which could allow laser spectroscopy to be carried out(17). Its atomic structure is unique owing to the absence of hyperfine interactions(18,19) between the spin-0 pi(-) and the He-4 nucleus. Here we synthesize pi He-4(+) in a superfluid-helium target and excite the transition (n, l) = (17, 16) -> (17, 15) of the pi(-)-occupied pi He-4(+) orbital at a near-infrared resonance frequency of 183,760 gigahertz. The laser initiates electromagnetic cascade processes that end with the nucleus absorbing the pi(-) and undergoing fission(20,21). The detection of emerging neutron, proton and deuteron fragments signals the laser-induced resonance in the atom, thereby confirming the presence of pi He-4(+). This work enables the use of the experimental techniques of quantum optics to study a meson.


Long-lived pionic helium atoms (composed of a helium-4 nucleus, an electron and a negatively charged pion) are synthesized in a superfluid-helium target, as confirmed by laser spectroscopy involving the pion-occupied orbitals.


  
Spin squeezing of 10(11) atoms by prediction and retrodiction measurements 期刊论文
NATURE, 2020, 581 (7807) : 159-+
作者:  Lan, Jun;  Ge, Jiwan;  Yu, Jinfang;  Shan, Sisi;  Zhou, Huan;  Fan, Shilong;  Zhang, Qi;  Shi, Xuanling;  Wang, Qisheng;  Zhang, Linqi;  Wang, Xinquan
收藏  |  浏览/下载:8/0  |  提交时间:2020/07/03

The measurement sensitivity of quantum probes using N uncorrelated particles is restricted by the standard quantum limit(1), which is proportional to 1/root N. This limit, however, can be overcome by exploiting quantum entangled states, such as spin-squeezed states(2). Here we report the measurement-based generation of a quantum state that exceeds the standard quantum limit for probing the collective spin of 10(11) rubidium atoms contained in a macroscopic vapour cell. The state is prepared and verified by sequences of stroboscopic quantum non-demolition (QND) measurements. We then apply the theory of past quantum states(3,4) to obtain spin state information from the outcomes of both earlier and later QND measurements. Rather than establishing a physically squeezed state in the laboratory, the past quantum state represents the combined system information from these prediction and retrodiction measurements. This information is equivalent to a noise reduction of 5.6 decibels and a metrologically relevant squeezing of 4.5 decibels relative to the coherent spin state. The past quantum state yields tighter constraints on the spin component than those obtained by conventional QND measurements. Our measurement uses 1,000 times more atoms than previous squeezing experiments(5-10), with a corresponding angular variance of the squeezed collective spin of 4.6 x 10(-13) radians squared. Although this work is rooted in the foundational theory of quantum measurements, it may find practical use in quantum metrology and quantum parameter estimation, as we demonstrate by applying our protocol to quantum enhanced atomic magnetometry.


  
The Buffer Zone of the Quasi-Biennial Oscillation 期刊论文
JOURNAL OF THE ATMOSPHERIC SCIENCES, 2019, 76 (11) : 3553-3567
作者:  Match, Aaron;  Fueglistaler, Stephan
收藏  |  浏览/下载:6/0  |  提交时间:2020/02/17
Quasibiennial oscillation  Stratospheric circulation  Stratosphere-troposphere coupling  Tropopause  Angular momentum  Reanalysis data  
Axisymmetric Constraints on Cross-Equatorial Hadley Cell Extent 期刊论文
JOURNAL OF THE ATMOSPHERIC SCIENCES, 2019, 76 (6) : 1547-1564
作者:  Hill, Spencer A.;  Bordoni, Simona;  Mitchell, Jonathan L.
收藏  |  浏览/下载:4/0  |  提交时间:2019/11/26
Atmosphere  Hadley circulation  Angular momentum  Climate models  
Annual and seasonal tornado activity in the United States and the global wind oscillation 期刊论文
CLIMATE DYNAMICS, 2018, 50: 4323-4334
作者:  Moore, Todd W.
收藏  |  浏览/下载:2/0  |  提交时间:2019/04/09
United States  Tornado variability  Global wind oscillation  Atmospheric angular momentum  
Impact of variability and anisotropy in the correlation decay distance for precipitation spatial interpolation in China 期刊论文
CLIMATE RESEARCH, 2018, 74 (1) : 81-93
作者:  Zhang, Yingxian;  Hidalgo, Jose;  Parker, David
收藏  |  浏览/下载:8/0  |  提交时间:2019/04/09
Daily precipitation  Correlation decay distance  Angular  distance weighting interpolation  
Final Report for "Interdecadal climate regime transition and its interaction with climate change in CMIP5 simulations" (DOE Grant DE-SC0005344) 科技报告
来源:US Department of Energy (DOE). 出版年: 2013
作者:  Huang, Huei-Ping [Arizona State University]
收藏  |  浏览/下载:4/0  |  提交时间:2019/04/05
Climate change  Climate modeling  Atmospheric angular momentum