Witness of topological phase transition and Weyl points in an open topological system

Recently, the tunable Weyl-semimetal bands and the associate topological phase transition have been successfully simulated in superconducting quantum circuits [X. Tan, \textit{et al.} Phys. Rev. Lett. {\bf 122}, 010501 (2019)]. Since the superconducting quantum circuits inevitably couple to the environment, we here focus on the steady state and decoherence process by taking the reservoir into consideration via quantum master equation. Our results show that the purity of the steady state can be used to indicate the topological phase transition and Weyl points. Furthermore, the coherence will exponentially decay to zero at the Weyl points, and decay to a nonzero value with oscillation at other points in the momentum space. Our work may have significant impact on the study of quantum open topological system.Comment: 5 pages, 4 figure

Non-adiabatic holonomic quantum computation in linear system-bath coupling

Non-adiabatic holonomic quantum computation in decoherence-free subspaces protects quantum information from control imprecisions and decoherence. For the non-collective decoherence that each qubit has its own bath, we show the implementations of two non-commutable holonomic single-qubit gates and one holonomic nontrivial two-qubit gate that compose a universal set of non-adiabatic holonomic quantum gates in decoherence-free-subspaces of the decoupling group, with an encoding rate of $\frac{N-2}{N}$. The proposed scheme is robust against control imprecisions and the non-collective decoherence, and its non-adiabatic property ensures less operation time. We demonstrate that our proposed scheme can be realized by utilizing only two-qubit interactions rather than many-qubit interactions. Our results reduce the complexity of practical implementation of holonomic quantum computation in experiments. We also discuss the physical implementation of our scheme in coupled microcavities.Comment: 2 figures; accepted by Sci. Re

The Longest Common Exemplar Subsequence Problem

In this paper, we propose to find order conserved subsequences of genomes by finding longest common exemplar subsequences of the genomes. The longest common exemplar subsequence problem is given by two genomes, asks to find a common exemplar subsequence of them, such that the exemplar subsequence length is maximized. We focus on genomes whose genes of the same gene family are in at most s spans. We propose a dynamic programming algorithm with time complexity O(s4 s mn) to find a longest common exemplar subsequence of two genomes with one genome admitting s span genes of the same gene family, where m, n stand for the gene numbers of those two given genomes. Our algorithm can be extended to find longest common exemplar subsequences of more than one genomes

A Deep Learning Approach to Generating Photospheric Vector Magnetograms of Solar Active Regions for SOHO/MDI Using SDO/HMI and BBSO Data

Solar activity is usually caused by the evolution of solar magnetic fields. Magnetic field parameters derived from photospheric vector magnetograms of solar active regions have been used to analyze and forecast eruptive events such as solar flares and coronal mass ejections. Unfortunately, the most recent solar cycle 24 was relatively weak with few large flares, though it is the only solar cycle in which consistent time-sequence vector magnetograms have been available through the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) since its launch in 2010. In this paper, we look into another major instrument, namely the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO) from 1996 to 2010. The data archive of SOHO/MDI covers more active solar cycle 23 with many large flares. However, SOHO/MDI data only has line-of-sight (LOS) magnetograms. We propose a new deep learning method, named MagNet, to learn from combined LOS magnetograms, Bx and By taken by SDO/HMI along with H-alpha observations collected by the Big Bear Solar Observatory (BBSO), and to generate vector components Bx' and By', which would form vector magnetograms with observed LOS data. In this way, we can expand the availability of vector magnetograms to the period from 1996 to present. Experimental results demonstrate the good performance of the proposed method. To our knowledge, this is the first time that deep learning has been used to generate photospheric vector magnetograms of solar active regions for SOHO/MDI using SDO/HMI and H-alpha data.Comment: 15 pages, 6 figure

Improved Method to Determine Standard Values of Mechanical Properties of Original Bamboo

The standard values of mechanical properties are important performance indexes of original bamboo as a sustainable building material. Such values should be determined by combining the requirement of confidence level and the number of samples. In this paper, systematic tests of longitudinal compression, bending, longitudinal tensile, longitudinal shear, transverse compression, and transverse tensile of bamboo were performed. Based on parametric and non-parametric methods, the influencing factors of the standard values of mechanical properties of bamboo were analyzed. A calculation method and prediction formulas were proposed and the standard values of mechanical properties of bamboo were determined. The results show that the choice of parametric method to calculate the standard value of bamboo strength in the case of a small number of samples may lead to distortion of the results, and the use of non-parametric analysis can effectively reduce the error

Ore-Forming Processes at the Xiajinbao Gold Deposit in Eastern Hebei Province: Constraints from EPMA and LA-ICPMS Analysis

The Xiajinbao gold deposit is located at the northern margin of the North China Craton. Hydrothermal pyrites belonging to three stages were identified: Py1; Py2; and Py3. Geochemical study of these pyrites was conducted using electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry to investigate the distributions of minor and trace elements, constrain pyrite genesis, and to obtain an improved understanding of the ore-forming processes. Py1 and Py2 contain high concentrations of Au and are interpreted to have been deposited from fluids from a dominantly magmatic source. Py3 grains have the lowest Co/Ni ratios. All generations of pyrite were deposited by mixing of meteoric waters with magmatic-hydrothermal fluids. Boiling of early ore-forming fluids led to the precipitation of Py1 and gold. Decreasing fO2 in the ore-forming system resulted in the formation of Py2 and gold. Fluid mixing was the dominant controlling factor for the precipitation of Py3 together with small amounts of gold

Nonlinear Landau-Zener tunneling in Majorana’s stellar representation

By representing the evolution of a quantum state with the trajectories of the stars on a Bloch sphere, the Majorana’s stellar representation provides an intuitive way to understand quantum motion in a high dimensional projective Hilbert space. In this work we show that the Majorana’s representation offers a very interesting and intuitive way to understand the nonlinear Landau-Zener tunneling. In particular, the breakdown of adiabaticity in this tunneling phenomenon can be understood as some of the stars never reaching the south pole. We also establish a connection between the Majorana stars in the second quantized model and the single star in the mean field model by using the reduced density matrix

Major and Trace Element Geochemistry of Pyrite and Pyrrhotite from Stratiform and Lamellar Orebodies: Implications for the Ore Genesis of the Dongguashan Copper (Gold) Deposit, Eastern China

The Dongguashan copper (gold) deposit in Anhui Province is one of the largest copper (gold) deposits in the Tongling ore district, which is the most important region in the Middle–Lower Yangtze River Metallogenic Belt, Eastern China. Stratiform and lamellar orebodies are the major deposit types. Pyrite and pyrrhotite from the stratiform deposit type (Py I, Po I) and lamellar deposit type (Py II, Po II) are investigated using Electron-probe Microanalyses (EPMA) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Py I, Py II, Po I and Po II have high contents of Cu, Co, Au and Se, low contents of As, Pb and Zn, with Co/Ni ratios of 0.50−48.00, 4.00−45.00, 1.55−14.45 and 1.02−1.36, respectively, most of which are greater than 1 and vary widely; these characteristics are consistent with those of pyrite with a magmatic–hydrothermal origin. The higher Au/Ag and Fe/(S + As) ratios of pyrite and crystallization temperatures (286–387 °C) of hexagonal pyrrhotite indicate that the mineralization occurrs in environments with medium- to high-temperatures, high sulfur fugacity and medium-shallow depths. Therefore, we suggest that the Dongguashan copper (gold) deposit is a stratabound skarn-type ore deposit associated with magma intrusion activity during the Yanshanian Period