compilation | Li Yan
Nature , 25 February 2021, Volume 590span2 strong 25 February 2021, strongspan2 _strongspan2 _strong5span2 25th Issue _p7span2 strong 25th issue 7847 _strongspan2 volume 590, 7847
physical
Physics
The asymmetry of antimatter in the proton
Proton _span4sp strong br _span4sp strong br _span 4sp strong ▲ Author:. J Dove, B. Kerns, RE McClellan, S. Miyasaka, DH Morton, et al
▲ link:.
https: // www. nature.com/articles/s41586-021-03282-z
▲ Summary
_span_span4 It has been known years ago.However, we still have only an incomplete theoretical and experimental understanding of how these particles and their dynamics produce the quantum bound state of protons and their physical properties (such as spin ).
The two up quarks and one down quark that make up a proton account for only a few percent of the proton's mass in the simplest case, and most of the proton's mass is based on quark kinetic energy and potential energy and from a strong force. Gluon can exist in the form of energy.
One of the basic characteristics of this force, as described by quantum chromodynamics, is that it can create matter-antimatter quark pairs that only exist for a short time inside the proton. Their short-lived existence makes antimatter quarks in protons difficult to study, but their existence can be distinguished in the reaction of matter-antimatter quarks to annihilation.
In this quark-antiquark scene produced by a strong force, the probability distribution of the existence of two antimatter quarks as a function of momentum should be almost the same because of their The mass is very similar and small compared to the mass of the proton.
Here, we provide evidence from the meson pair generation measurement. These distributions are different. In a large range of momentum, there are more lower antimatter quarks than upper antimatter quarks. These results are expected to rekindle interest in several mechanisms of the origin of antimatter asymmetry in protons, and point out that future measurements can distinguish these mechanisms.
Angular momentum generation in the angular nuclear fission
nuclear fission generating momentum
▲ oF: JN Wilson, D. Thisse, M. Lebois, N. Jovančević, et al
▲ link:.
https://www.nature.com/articles/s41586-021-03304-w
strong2 4 _span_strong1span strong1 4 _span_strong2 4 _span_strong1 Fission),The resulting debris will be observed rotating; this phenomenon has been a mystery in nuclear physics for more than 40 years.
For systems with zero or almost zero spin, 6 or 7 units of angular momentum are usually generated in each fragment. The internal generation of is particularly confusing.
Here, we show that there is no significant correlation between the spins of the fragments, which leads us to conclude that the angular momentum in fission is actually generated after nuclear fission. We have provided comprehensive data showing that the average spin is strongly dependent on mass and has a zigzag distribution. We observe that the spin of the fragment has no obvious dependence on the mass or charge of the companion nucleus, confirming the irrelevant post-fragmentation nature of the spin mechanism.
To explain these observations, we propose that the collective movement of the nucleus in the fractured neck of the fission system produces two independent moments, similar to the fracture of a rubber band. According to statistical theory, the parameterization method based on angular momentum state occupancy describes the entire range of experimental data well.
Experimental demonstration of the mechanism of steady-state microbunching
steady micro experimental demonstration bunching principle of
▲ author: Xiujie Deng, Alexander Chao, Jörg Feikes, Arne Hoehl, et al
▲ link:
https://www.nature.com/articles/s41586-021-03203-0
2 ▲ Based on the principle of micro-span ▲ (SSMB),It can obtain coherent radiation with high power, high repetition frequency and narrow bandwidth, and the wavelength can cover from terahertz to extreme ultraviolet (EUV) band. This is achieved by using micro-bunching to make multi-particle coherent enhancement of the radiation in the electron storage ring on a steady-state round-by-round basis. In order to reveal the potential of SSMB as the future source of photon , the key is to demonstrate its principle on a real machine. Here, we report an experimental demonstration of the principle of SSMB. Our research has shown that the electron beam is stored in a quasi-isochronous ring. After the laser-induced energy modulation with a wavelength of 1064 nanometers, it can generate submicron micro-beams and coherent radiation. Our results confirm that the optical phase of electrons can be correlated circle by circle with an accuracy shorter than the laser wavelength. On this basis, we expect to realize SSMB by applying phase-locked lasers and electrons to interact in turn. This demonstration represents a milestone in the realization of a high-repetition, high-power photon source based on the SSMB principle. quantum communication Quantum Communications deterministic multi-qubit entanglement in a quantum network quantum network in uncertain multi-qubit entanglement ▲ author: Youpeng Zhong, Hung-Shen Chang, Audrey Bienfait, et al. ▲ Link:
g https://www.nature.com/articles/s41586-021-03288-7
▲ Abstract p p in large-scale communication in quantum computing ,Generating high-fidelity distributed multi- qubit entanglement is a challenging task.
The deterministic entanglement of two remote qubits has recently been demonstrated by photons and phonons. However, due to the limited state transmission fidelity, the deterministic generation and transmission of multi-qubit entanglement has not been confirmed.
Here, we report a quantum network composed of two superconducting quantum nodes, the nodes are connected by a one-meter-long superconducting coaxial cable, each node contains three interconnected qubit . By directly connecting a cable to a qubit of each node, we transfer quantum states between nodes, with a process fidelity of 0.911±0.008.
We also prepared a three-bit GHZ state on one node and transferred it to another node. The fidelity of the transition state is 0.656±0.014. We further use this system to deterministically generate a globally distributed two-node six-bit GHZ state with a state fidelity of 0.722±0.021.
artificial intelligence
Artificial Intelligence
First return, then explore
First return,And then explore
▲ Author: Adrien Ecoffet, Joost Huizinga, Joel Lehman, Kenneth O. Stanley & Jeff Clune
▲ link:
https://www.nature.com/articles/s41586-020-03157-9
▲ Summary _strong5span _span4 p To automatically solve complex sequential decision-making problems. However, when simple and intuitive rewards provide small and deceptive feedback, reinforcement learning algorithms get stuck.
Here, we assume that the main obstacle to effective exploration comes from the algorithm forgetting how to reach the previously visited state (separation) and the failure to return to the original state (derailed) before exploration.
We introduced Go-Explore,This is a series of algorithms that directly solve these two challenges by clearly "remembering" promising states and returning to them before deliberately exploring the simple principles.
Go-Explore solves all the previously unsolved Atari games, and surpasses the technical level of all difficult exploration games, and has made orders of magnitude in games such as Montezuma’s Revenge and The Trap improvement of. We also showed the actual potential of Go-Explore in the less rewarding pick-and-place robot task.
In addition, we also found that adding a target condition strategy can further improve the exploration efficiency of Go-Explore and enable it to deal with the randomness of the entire training process.
Material Science
materials science
Efficient perovskite solar cells via improved carrier management
enhanced charge carrier management,Perovskite efficient solar cell
▲ OF:. Jason J. Yoo, Gabkyung Seo, Matthew R. Chua, Tae Gwan Park, et al
▲ Link:
https://www.nature.com/articles/s41586-021-03285-w _strongspan1 _strongspan1 _span4 The improvement of
charge carrier management is closely related to fill factor and open circuit voltage, which provides a way to improve the device performance of PSCs and reach their theoretical efficiency limit. Here, we report an overall approach to improve the performance of PSCs by enhancing charge carrier management.
First, by adjusting the tin dioxide deposited by the electroless plating solution, we obtained an electron transport layer with an ideal film coverage, thickness and composition.
Second, we decouple the passivation strategy between the block and the interface to improve performance while minimizing band gap loss. In the forward bias, our device exhibits an electroluminescence external quantum efficiency as high as 17.2% and an electroluminescence energy conversion efficiency as high as 21.6%.
As solar cells, they obtain a certified energy conversion efficiency of 25.2%, which is equivalent to 80.5% of their band gap thermodynamic limit.
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