Nature,17 March 2022, Volume 603, No.7901

Nature, March 2022 17, vol. 603, No.790 1.

Chemical chemistry

High resolution laser resonance of antiproton helium in superfluid 4He

High resolution laser oscillation of antiproton helium in superfluid 4He

Authors: Anna Só té r, Hossein Aghai-Khozani and others.

Link:

/articles/s 4 1586-022-04440-7

abstract

Here, we show that when a strange helium atom with antiproton composition is embedded in superfluid helium, its visible wavelength line keeps sub-gigahertz linewidth. When the liquid around the atom becomes superfluid phase, the vibration linewidth of antiproton laser suddenly decreases.

This solves the hyperfine structure produced by the spin-spin interaction between electrons and antiprotons, and the relative spectral resolution is 106, although antiproton helium is located in the dense matrix of normal matter atoms. During laser excitation, the electron shell of antiproton atom keeps a small radius of about 40 picometers.

This means that laser spectroscopy with high spectral resolution can be used to study other helium atoms with antinuclear and negatively charged mesons and hyperons, including strange quarks formed in superfluid helium, so as to determine the mass of particles. Clear spectral lines can detect antiprotons of cosmic rays and search for deuterium trapped in liquid helium targets.

abstract

Here, we prove that when a foreign helium atom containing an antiproton is embedded in superfluid helium, its visible wavelength spectral line keeps sub-gigahertz linewidth. When the liquid around the atom changes into superfluid phase, it is observed that the linewidth of antiproton laser resonance suddenly decreases. This solves the hyperfine structure caused by the spin-spin interaction between electrons and antiprotons, and the relative spectral resolution is two parts of 106, even though antiproton helium exists in the dense matrix of normal matter atoms. During laser excitation, the electron shell of antiproton atom keeps a small radius of about 40 picometers. This means that other helium atoms with antinuclear, as well as negatively charged mesons and hyperons, including strange quarks formed in superfluid helium, can be studied by laser spectroscopy with high spectral resolution, so as to determine the particle mass. Sharp spectral lines may be helpful to detect cosmic ray antiprotons or to find antineutrinos staying in liquid helium targets.

Planar-assisted self-regulating antioxidant properties of Cu (11).

Copper thin film material Cu( 1 1 1) with flat surface and self-adjusting oxidation resistance.

Authors: Sujae Kim, Yong in Kim, Bip in Lamichane, etc.

Link:

/articles/s 4 1586-02 1-04375-5 # sec 9

abstract

Oxidation will reduce the performance of copper, and the performance of copper is very important for its use, especially in semiconductor industry and electro-optical applications. Here, we show the preparation of semi-permanent oxidation-resistant copper films, because they are composed of flat surfaces with only occasional monoatomic steps. First-principles calculation proves that the edge of the monatomic step is as unaffected by oxygen as the flat surface, and once the surface position coverage of the oxygen face-centered cubic FCC reaches 50%, the surface adsorption of oxygen atoms is inhibited. These comprehensive effects explain the special oxidation resistance of ultra-flat copper surface.

abstract

Oxidation will damage the properties of copper, which are very important for the use of copper, especially in semiconductor industry and electro-optical applications. Here, we report the preparation of semi-permanent oxidation-resistant copper thin films, because they are composed of flat surfaces with only occasional monoatomic steps. First-principles calculation proves that the edge of monatomic step is as impermeable to oxygen as the flat surface, and once the site coverage of oxygen face-centered cubic (f cc) reaches 50%, the surface adsorption of oxygen atoms is inhibited. These comprehensive effects explain the excellent oxidation resistance of ultra-flat copper surface.

Physics physics

Solving partial fermion quantum Monte Carlo with quantum computer

Unbiased Fermion Quantum Monte Carlo and Quantum Computer

Authors: William J. Huggins, Brian A. Ogman, Nicholas C. Rubin, David R. Reichman, Ryan Babus &; Li junhao

Link:

/articles/s 4 1586-02 1-0435 1-z

abstract

Using constraints to control Fermi symbols ensures the efficiency of quantum Monte Carlo calculation (QMC), but at the cost of limited flexibility of classical calculation, there may be significant deviations.

Here, we propose a method combining QMC and quantum computing to reduce this deviation. Our scheme was realized in the experiment. We use as many as 16 qubits to calculate unbiased QMC, and these calculations are carried out on chemical systems with as many as 120 orbitals.

With the help of quantum computer, these experiments represent the largest chemical simulation, and at the same time, they reach the accuracy that competes with the most advanced classical methods without reducing the burden of errors.

Compared with the popular variable component quantum solver, our quantum-classical hybrid calculation model provides another way to realize the actual quantum advantage for electronic structure problems, and it is not necessary to prepare and measure the ground state wave function very accurately.

abstract

Due to the limited flexibility of classical calculation, at the expense of potential significant deviation, the efficiency of QMC is ensured by using constraints to control fermion symbol problems. Here, we propose a method to reduce this deviation by combining limited QMC and quantum computing. We experimentally use up to 16 qubits to realize our scheme to remove the bias constraint QMC calculation performed on chemical systems with up to 6 5438+020 orbits. These experiments represent the largest chemical simulation with the help of quantum computer, and at the same time, they achieve the accuracy comparable to the most advanced classical methods without heavy error reduction. Compared with all kinds of popular quantum eigensolvers, our mixed quantum classical calculation model provides another way to obtain practical quantum advantages in electronic structure problems without the need to prepare and measure ground state wave functions very accurately.

Strong wind propagation of battery-free wireless devices

Battery-less wireless device with wind diffusion

Authors: Vic Lamier, Hans Gainesball, Thomas Daniel &; Shyam Nat Gorakota

Link:

/articles/s 4 1586-02 1-04363-9

abstract

Plants cover a large part of the earth's land, although most species cannot move. In order to transport and reproduce offspring, many plants have evolved the mechanism of wind-borne seeds.

For example, dandelion seeds have bristle-like filamentous structures, which can slow down the terminal speed and help them locate when floating to the ground. Inspired by this, we show the battery-free wireless wind diffusion sensing equipment here. Our millimeter-scale equipment weighs 30 mg, is based on flexible substrates, and uses programmable and off-the-shelf components to provide scalability and flexibility for various sensing and computing applications.

The system is powered by light solar cells and energy collection circuits. The circuit is very stable under the conditions of low illumination and variable illumination, and has a backscattering communication link, which can realize data transmission.

In order to realize the large-area dispersion and vertical landing necessary for solar energy collection, we developed a dandelion-inspired membrane porous structure, with a terminal speed of 0.87 0.02 m/s, aerodynamic stability and a vertical landing probability of over 95%. The results of outdoor environment experiments show that these devices can move 50- 100 meters in mild to normal breeze.

Finally, in the natural system, the morphological differences of individual seeds cause some seeds to fall closer, while others spread farther. We adopted a similar method and showed how to adjust the porosity and diameter of the structure to realize the dispersion change between devices.

abstract

Plants cover a large part of the earth's land, although most species have limited mobility. In order to transport their propagules, many plants have evolved the mechanism of spreading seeds by wind. For example, dandelion seeds have a bristle-like filament structure, which reduces its final speed and helps the seeds to orient when floating to the ground. Inspired by this, we demonstrated the wind propagation of battery-free wireless sensing equipment. Our millimeter equipment weighs 30? Mg, designed on flexible substrate with programmable off-the-shelf devices, provides scalability and flexibility for various sensing and computing applications. The system is powered by a light solar cell and an energy collection circuit, which is robust to weak light and variable light conditions and has a backscattering communication link supporting data transmission. In order to realize the large-area dispersion and vertical landing required for solar energy collection, we developed a thin film porous structure inspired by dandelion, and achieved a terminal speed of 0.87? 0.02? Rice? Every second and aerodynamic stability, the probability of vertical landing exceeds 95%. Our test results in outdoor environment show that these devices can run at 50–100? In the breeze of rice. Finally, in the natural system, the differences of individual seed morphology lead some seeds to fall closer, while others go further. We adopt a similar method and show how to adjust the porosity and diameter of the structure to realize the dispersion change between devices.

earth sciences

Limited increase of carbon storage in savanna during decades of fire fighting.

The growth of carbon storage in savanna without fire for decades is limited.

Authors: Zhou Yong, Dzheniya Singh, John R. Butnoel, Colley Cortesi, Peter B. Boucher, Madelon F. Case, Evan G. Hockridge, Andrew B. Davis &; A. Carla staff

Link:

/articles/s 4 1586-022-04438- 1

abstract

Here, for the first time, we directly evaluated the carbon response of the entire ecosystem of African wetland grassland without fire for 60 years.

We found that fire extinguishing only increased the carbon storage of the whole ecosystem by 35.4 12% (the standard error of the average), even if the tree coverage increased by 78.9 29.3%, the corresponding total income was 23.0 6. 1 Mg? c？ Ha 1 is about 0.35±0.09Mg on average? c？ Ha 1 year 1 is lower than previously thought.

There is a lot of carbon that is often burned under the savanna, especially in biomass and deep soil. These underground reservoirs have not been fully considered in the afforestation or fire fighting plan, but this may mean that the storage potential of savanna in ten years can be ignored, especially compared with the subsequent loss of biodiversity and function.

abstract

Here, we provide a carbon response of more than 60? Fire elimination of savanna in central Africa for many years. We found that although the forest coverage rate increased by 78.9 29.3%, fire fighting only increased the carbon storage of the whole ecosystem by 35.412% (I am a standard error), which is equivalent to a total income of 23.0 6.1? Mg? c？ Ha 1 is about 0.35 0.09 on average? Mg? c？ ha 1？ 1 year, which is more than one order of magnitude lower than previously assumed. The burning savanna has a lot of underground carbon, especially in biomass and deep soil. These underground reservoirs have not been fully considered in the afforestation or fire fighting plan, but this may mean that the ten-year storage potential of savanna can be ignored, especially considering the accompanying loss of biodiversity and function.

Chemical chemistry

New land-use change emissions show that the proportion of carbon dioxide airborne is decreasing.

New land use change emissions show that the proportion of carbon dioxide in the air is decreasing.

Authors: Margaret J.E. Van Mahler, Dave Van Weiss, Richard A. Horton, Robert D. Field, Jane Webster &; Guido. Van der Werff

Link:

/articles/s 4 1586-02 1-04376-4

abstract

Here, we use visibility data to construct an emission data set of key deforestation areas of land use and land cover change (LULCC). These visibility observations are related to fire emissions, which are related to land use, land use change and climate change. Although this is indirect, it provides a long-term consistent data set of LULCC emissions, which shows that the emissions from tropical deforestation have increased greatly since 1958 began to measure CO2 concentration.

So far, these emissions are considered to be relatively stable, resulting in an increasing proportion in the air. However, our results show that the CO2 content in the atmosphere has decreased by 0.0140.010decade1since 1959. This shows that the growth rate of land-ocean joint sinks is at least as fast as that of man-made emissions.

abstract

Here, we use the visibility data of key deforestation areas to construct a LULCC emission data set. These visibility observations are substitutes for fire emissions, which are related to land use, land use change and climate change. Although indirect, this provides a long-term consistent data set of land use, land-use change and climate change emissions, indicating that tropical deforestation emissions have increased significantly (0. 16? Pg？ c？ Ten years 1) Since CO2 concentration measurement was started in 1958. So far, these emissions are considered to be relatively stable, leading to an increase in the proportion of air transmission. However, our results show that the carbon dioxide content in the air has decreased by 0.0 14? Decimal 1 since 1959. This shows that the total absorption of land and sea is increasing at least as fast as that of man-made emissions.