|
State Classification via a Random-Walk-Based Quantum Neural Network
Lu-Ji Wang, Jia-Yi Lin, and Shengjun Wu
Chin. Phys. Lett. 2022, 39 (5):
050301
.
DOI: 10.1088/0256-307X/39/5/050301
In quantum information technology, crucial information is regularly encoded in different quantum states. To extract information, the identification of one state from the others is inevitable. However, if the states are non-orthogonal and unknown, this task will become awesomely tricky, especially when our resources are also limited. Here, we introduce the quantum stochastic neural network (QSNN), and show its capability to accomplish the binary discrimination of quantum states. After a handful of optimizing iterations, the QSNN achieves a success probability close to the theoretical optimum, no matter whether the states are pure or mixed. Other than binary discrimination, the QSNN is also applied to classify an unknown set of states into two types: entangled ones and separable ones. After training with four samples, it can classify a number of states with acceptable accuracy. Our results suggest that the QSNN has the great potential to process unknown quantum states in quantum information.
|
|
Network-Initialized Monte Carlo Based on Generative Neural Networks
Hongyu Lu, Chuhao Li, Bin-Bin Chen, Wei Li, Yang Qi, and Zi Yang Meng
Chin. Phys. Lett. 2022, 39 (5):
050701
.
DOI: 10.1088/0256-307X/39/5/050701
We design generative neural networks that generate Monte Carlo configurations with complete absence of autocorrelation from which only short Markov chains are needed before making measurements for physical observables, irrespective of the system locating at the classical critical point, fermionic Mott insulator, Dirac semimetal, or quantum critical point. We further propose a network-initialized Monte Carlo scheme based on such neural networks, which provides independent samplings and can accelerate the Monte Carlo simulations by significantly reducing the thermalization process. We demonstrate the performance of our approach on the two-dimensional Ising and fermion Hubbard models, expect that it can systematically speed up the Monte Carlo simulations especially for the very challenging many-electron problems.
|
|
Structural Evolution of $D_{5h}$(1)-C$_{90}$ under High Pressure: A Mediate Allotrope of Nanocarbon from Zero-Dimensional Fullerene to One-Dimensional Nanotube
Yan Wang, Mingguang Yao, Xing Hua, Fei Jin, Zhen Yao, Hua Yang, Ziyang Liu, Quanjun Li, Ran Liu, Bo Liu, Linhai Jiang, and Bingbing Liu
Chin. Phys. Lett. 2022, 39 (5):
056101
.
DOI: 10.1088/0256-307X/39/5/056101
The hybridization of fullerene and nanotube structures in newly isolated C$_{90}$ with the $D_{5h}$ symmetric group ($D_{5h}$(1)-C$_{90}$) provides an ideal model as a mediating allotrope of nanocarbon from zero-dimensional (0D) fullerene to one-dimensional nanotube. Raman and infrared spectroscopy combined with classical molecular dynamics simulation were used to investigate the structural evolution of $D_{5h}$(1)-C$_{90}$ at ambient and high pressure up to 35.1 GPa. Interestingly, the high-pressure transformations of $D_{5h}$(1)-C$_{90}$ exhibit the features of both fullerene and nanotube. At around 2.5 GPa, the $D_{5h}$(1)-C$_{90}$ molecule in the crystal undergoes an orientational transition to a restricted rotation. At 6.6 GPa, the tubular hexagonal part occurs and transforms into a dumbbell-like structure at higher pressure. The material starts to amorphize above 13.9 GPa, and the transition is reversible until the pressure exceeds 25 GPa. The amorphization is probably correlated with both the intermolecular bonding and the morphology change. Our results enrich our understanding of structural changes in nanocarbon from 0D to 1D.
|
|
Pressure-Driven Ne-Bearing Polynitrides with Ultrahigh Energy Density
Lulu Liu, Shoutao Zhang, and Haijun Zhang
Chin. Phys. Lett. 2022, 39 (5):
056102
.
DOI: 10.1088/0256-307X/39/5/056102
Neon (Ne) can reveal the evolution of planets, and nitrogen (N) is the most abundant element in the Earth's atmosphere. Considering the inertness of neon, whether nitrogen and neon can react has aroused great interest in condensed matter physics and space science. Here, we identify three new Ne–N compounds (i.e., NeN$_6$, NeN$_{10}$, and NeN$_{22}$) under pressure by first-principles calculations. We find that inserting Ne into N$_2$ substantially decreases the polymeric pressure of the nitrogen and promotes the formation of abundant polynitrogen structures. Especially, NeN$_{22}$ acquires a duplex host-guest structure, in which guest atoms (Ne and N$_2$ dimers) are trapped inside the crystalline host N$_{20}$ cages. Importantly, both NeN$_{10}$ and NeN$_{22}$ not only are dynamically and mechanically stable but also have a high thermal stability up to 500 K under ambient pressure. Moreover, ultra-high energy densities are obtained in NeN$_{10}$ (11.1 kJ/g), NeN$_{22}$ (11.5 kJ/g), tetragonal t-N$_{22}$ (11.6 kJ/g), and t-N$_{20}$ (12.0 kJ/g) produced from NeN$_{22}$, which are more than twice the value of trinitrotoluene (TNT). Meanwhile, their explosive performance is superior to that of TNT. Therefore, NeN$_{10}$, NeN$_{22}$, t-N$_{22}$, and t-N$_{20}$ are promising green high-energy-density materials. This work promotes the study of neon-nitrogen compounds with superior properties and potential applications.
|
|
Quantum Hydrodynamics of Fractonic Superfluids with Lineon Condensate: From Navier–Stokes-Like Equations to Landau-Like Criterion
Jian-Keng Yuan, Shuai A. Chen, and Peng Ye
Chin. Phys. Lett. 2022, 39 (5):
057101
.
DOI: 10.1088/0256-307X/39/5/057101
Fractonic superfluids are exotic states of matter with spontaneously broken higher-rank $U(1)$ symmetry. The broken symmetry is associated with conserved quantities, including not only particle number (i.e., charge) but also higher moments, such as dipoles, quadrupoles, and angular moments. Owing to the presence of such conserved quantities, the mobility of particles is restricted either completely or partially. Here, we systematically study the hydrodynamical properties of fractonic superfluids, especially focusing on the fractonic superfluids with conserved angular moments. The constituent bosons are called “lineons” with $d$ components in $d$-dimensional space. From the Euler–Lagrange equation, we derive the continuity equation and Navier–Stokes-like equations, in which the angular moment conservation introduces extra terms. Further, we discuss the current configurations related to the defects. Like the conventional superfluid, we study the critical values of velocity fields and density currents, which gives rise to a Landau-like criterion. Finally, several future directions are discussed.
|
|
Anisotropic Fermi Surfaces, Electrical Transport, and Two-Dimensional Fermi Liquid Behavior in Layered Ternary Boride MoAlB
Pan Nie, Huakun Zuo, Lingxiao Zhao, and Zengwei Zhu
Chin. Phys. Lett. 2022, 39 (5):
057102
.
DOI: 10.1088/0256-307X/39/5/057102
We report a study of fermiology, electrical anisotropy, and Fermi liquid properties in the layered ternary boride MoAlB, which could be peeled into two-dimensional (2D) metal borides (MBenes). By studying the quantum oscillations in comprehensive methods of magnetization, magnetothermoelectric power, and torque with the first-principle calculations, we reveal three types of bands in this system, including two 2D-like electronic bands and one complex three-dimensional-like hole band. Meanwhile, a large out-of-plane electrical anisotropy ($\rho_{bb}/\rho_{aa}\sim 1100$ and $\rho_{bb}/\rho_{cc}\sim 500$, at 2 K) was observed, which is similar to those of the typical anisotropic semimetals but lower than those of some semiconductors (up to $10^{5}$). After calculating the Kadowaki–Woods ratio (${\rm KWR} = A/\gamma^2$), we observed that the ratio of the in-plane $A_{a,c}/\gamma^2$ is closer to the universal trend, whereas the out-of-plane $A_{b}/\gamma^2$ severely deviates from the universality. This demonstrates a 2D Fermi liquid behavior. In addition, MoAlB cannot be unified using the modified KWR formula like other layered systems (Sr$_2$RuO$_4$ and MoOCl$_2$). This unique feature necessitates further exploration of the Fermi liquid property of this layered molybdenum compound.
|
|
Lieb Lattices Formed by Real Atoms on Ag(111) and Their Lattice Constant-Dependent Electronic Properties
Xiaoxia Li, Qili Li, Tongzhou Ji, Ruige Yan, Wenlin Fan, Bingfeng Miao, Liang Sun, Gong Chen, Weiyi Zhang, and Haifeng Ding
Chin. Phys. Lett. 2022, 39 (5):
057301
.
DOI: 10.1088/0256-307X/39/5/057301
Scanning tunneling microscopy is a powerful tool to build artificial atomic structures that do not exist in nature but possess exotic properties. In this study, we constructed Lieb lattices with different lattice constants by real atoms, i.e., Fe atoms on Ag(111), and probed their electronic properties. We obtain a surprising long-range effective electron wavefunction overlap between Fe adatoms as it exhibits a $\frac{1}{r^{2}}$ dependence with the interatomic distance $r$ instead of the theoretically predicted exponential one. Combining control experiments, tight-binding modeling, and Green's function calculations, we attribute the observed long-range overlap to being enabled by the surface state. Our findings enrich the understanding of the electron wavefunction overlap and provide a convenient platform to design and explore artificial structures and future devices with real atoms.
|
|
Unusual Band Splitting and Superconducting Gap Evolution with Sulfur Substitution in FeSe
Yuanyuan Yang, Qisi Wang, Shaofeng Duan, Hongliang Wo, Chaozhi Huang, Shichong Wang, Lingxiao Gu, Dong Qian, Jun Zhao, and Wentao Zhang
Chin. Phys. Lett. 2022, 39 (5):
057302
.
DOI: 10.1088/0256-307X/39/5/057302
High-resolution angle-resolved photoemission measurements were taken on FeSe$_{1-x}$S$_x$ ($x$ = 0, 0.04, and 0.08) superconductors. With an ultrahigh energy resolution of 0.4 meV, unusual two hole bands near the Brillouin-zone center, which was possibly a result of additional symmetry breaking, were identified in all the sulfur-substituted samples. In addition, in both of the hole bands highly anisotropic superconducting gaps with resolution limited nodes were evidenced. We find that the larger superconducting gap on the outer hole band is reduced linearly to the nematic transition temperature while the gap on the inner hole is nearly S-substitution independent. Our observations strongly suggest that the superconducting gap increases with enhanced nematicity although the superconducting transition temperature is not only governed by the pairing strength, demonstrating strong constraints on theories in the FeSe family.
|
|
Neutron Spectroscopy Evidence for a Possible Magnetic-Field-Induced Gapless Quantum-Spin-Liquid Phase in a Kitaev Material $\alpha$-RuCl$_3$
Xiaoxue Zhao, Kejing Ran, Jinghui Wang, Song Bao, Yanyan Shangguan, Zhentao Huang, Junbo Liao, Bo Zhang, Shufan Cheng, Hao Xu, Wei Wang, Zhao-Yang Dong, Siqin Meng, Zhilun Lu, Shin-ichiro Yano, Shun-Li Yu, Jian-Xin Li, and Jinsheng Wen
Chin. Phys. Lett. 2022, 39 (5):
057501
.
DOI: 10.1088/0256-307X/39/5/057501
As one of the most promising Kitaev quantum-spin-liquid (QSL) candidates, $\alpha$-RuCl$_3$ has received a great deal of attention. However, its ground state exhibits a long-range zigzag magnetic order, which defies the QSL phase. Nevertheless, the magnetic order is fragile and can be completely suppressed by applying an external magnetic field. Here, we explore the evolution of magnetic excitations of $\alpha$-RuCl$_3$ under an in-plane magnetic field, by carrying out inelastic neutron scattering measurements on high-quality single crystals. Under zero field, there exist spin-wave excitations near the $M$ point and a continuum near the $\varGamma$ point, which are believed to be associated with the zigzag magnetic order and fractional excitations of the Kitaev QSL state, respectively. By increasing the magnetic field, the spin-wave excitations gradually give way to the continuous excitations. On the verge of the critical field $\mu_0H_{\rm c}=7.5$ T, the former ones vanish and only the latter ones are left, indicating the emergence of a pure QSL state. By further increasing the field strength, the excitations near the $\varGamma$ point become more intense. By following the gap evolution of the excitations near the $\varGamma$ point, we are able to establish a phase diagram composed of three interesting phases, including a gapped zigzag order phase at low fields, possibly gapless QSL phase near $\mu_0H_{\rm c}$, and gapped partially polarized phase at high fields. These results demonstrate that an in-plane magnetic field can drive $\alpha$-RuCl$_3$ into a long-sought QSL state near the critical field.
|
|
In Situ Epitaxy of Pure Phase Ultra-Thin InAs-Al Nanowires for Quantum Devices
Dong Pan, Huading Song, Shan Zhang, Lei Liu, Lianjun Wen, Dunyuan Liao, Ran Zhuo, Zhichuan Wang, Zitong Zhang, Shuai Yang, Jianghua Ying, Wentao Miao, Runan Shang, Hao Zhang, and Jianhua Zhao
Chin. Phys. Lett. 2022, 39 (5):
058101
.
DOI: 10.1088/0256-307X/39/5/058101
We demonstrate the in situ growth of ultra-thin InAs nanowires with an epitaxial Al film by molecular-beam epitaxy. Our InAs nanowire diameter ($\sim $30 nm) is much thinner than before ($\sim $100 nm). The ultra-thin InAs nanowires are pure phase crystals for various different growth directions. Transmission electron microscopy confirms an atomically abrupt and uniform interface between the Al shell and the InAs wire. Quantum transport study on these devices resolves a hard induced superconducting gap and 2$e$-periodic Coulomb blockade at zero magnetic field, a necessary step for future Majorana experiments. By reducing wire diameter, our work presents a promising route for reaching fewer sub-band regime in Majorana nanowire devices.
|
|
Highly Sensitive Mid-Infrared Photodetector Enabled by Plasmonic Hot Carriers in the First Atmospheric Window
Yuan-Fang Yu, Ye Zhang, Fan Zhong, Lin Bai, Hui Liu, Jun-Peng Lu, and Zhen-Hua Ni
Chin. Phys. Lett. 2022, 39 (5):
058501
.
DOI: 10.1088/0256-307X/39/5/058501
The first atmospheric window of 3–5 µm in the mid-infrared (MIR) spectral range pertains to crucial application fields, with particular scientific and technological importance. However, conventional narrow-bandgap semiconductors operating at this band, represented by mercury cadmium telluride and indium antimonide, suffer from limited specific detectivity at room temperature and hindered optoelectronic integration. In this study, a plasmonic hot electron-empowered MIR photodetector based on Al-doped ZnO (AZO)/bi-layer graphene heterostructure is demonstrated. Free electrons oscillate coherently in AZO disk arrays, resulting in strong localized surface plasmon resonance (LSPR) in the MIR region. The photoelectric conversion efficiency at 3–5 µm is significantly improved due to plasmon-induced hot-electron extraction and LSPR-enhanced light absorption. The specific detectivity reaches about $1.4 \times 10^{11}$ Jones and responsivity is up to 4712.3 A/W at wavelength of 3 µm at room temperature. The device's specific detectivity is among the highest performance of commercial state-of-the-art photodetectors and superior to most of the other 2D materials based photodetectors in the MIR region. These results demonstrate that a plasmonic heavily doped metal oxides/2D material heterostructure is a suitable architecture for constructing highly sensitive room-temperature MIR photodetectors.
|
19 articles
|