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In this paper, a neural networks model for quantum computer is proposed. The core of this model is quantum neuron. Firstly, the inner product of the input qubits and the weight qubits is mapped to the phase of the control qubits in the neuron by the swap test technology, and then these phases are obtained by the phase estimation method, which are further used as the phase of the output qubit in the neuron. In this way, the mapping of input qubits to output qubit in quantum neuron is completed. The quantum neurons mentioned above can be used to construct quantum neural networks. In this paper, the quantum circuit for each operation step are given. The simulation results on the classic computer verify the effectiveness of the proposed model. [ABSTRACT FROM AUTHOR]

Compared with ferromagnetic counterparts, antiferromagnetic materials are considered as the future of spintronic applications since these materials are robust against the magnetic perturbation, produce no stray field, and display ultrafast dynamics. There are (at least) two sets of magnetic moments in antiferromagnets (AFMs) (with magnetization of the same magnitude but antiparallel directions) and ferrimagnets (with the magnetization of the different magnitude). The coupled dynamics of the bipartite collinear AFMs is modeled by a coupled system of Landau–Lifshitz–Gilbert equations with additional terms originated from the interlattice exchange, which leads to femtosecond magnetization dynamics in AFMs. In this article, we develop three Gauss–Seidel projection methods for micromagnetics simulation in AFMs and ferrimagnets. They are first-order accurate in time and second-order accurate in space, and only solve linear systems of equations with constant coefficients at each step. Femtosecond dynamics, Néel wall structure, and phase transition in the presence of an external magnetic field for AFMs are provided with the femtosecond stepsize. [ABSTRACT FROM AUTHOR]

Edge detection is a fundamental task in digital image processing. Marr–Hildreth edge detection is the basic tool for implementing edge detection in classic image processing. This paper studies the quantum version of the classical Marr–Hildreth edge detection, which includes two core processes: Gaussian–Laplacian filtering and zero-crossing extraction. Based on the sampling results of the Gaussian–Laplace function, Gaussian–Laplacian filtering is implemented directly using quantum multipliers and quantum adders. Zero-crossing extraction is achieved using several quantum comparators. The quantum circuits of these two core processes with several auxiliary operators are designed in detail. Complexity analysis shows that the quantum Marr–Hildreth edge detection has exponential speedup compared to its classical counterpart. The simulation on the classical computer verifies the correctness of the quantum Marr–Hildreth edge detection results. [ABSTRACT FROM AUTHOR]

In this paper, a design method of quantum circuits for threshold segmentation of gray-scale image is proposed, which is a quantum counterpart of classical optimum global thresholding using Otsu's method. First, we design a quantum circuit to obtain the histogram of the pixels distribution. Then, on this basis, we design the quantum circuits of some sub-modules, such as the cumulative histogram, cumulative mean, multiplication, division, the between-class variance and so on. Finally, all the between-class variances corresponding to each gray-level are sorted. At this time, the gray-level corresponding to the maximum of the between-class variance is the Otsu's threshold. For all the operations involved in the classical Otsu's threshold selection, we designed the corresponding quantum circuits, analyzed the computational complexity, and verified the correctness of these circuits by simulations on classical computers. [ABSTRACT FROM AUTHOR]

The vortex search is proposed as a new optimization algorithm recently. This algorithm has the advantages of simple operation and strong search capabilities. By introducing quantum computing into this algorithm, A quantum-inspired vortex search algorithm is presented in this paper. The initial population of the algorithm has only one individual called vortex center. First this individual is encoded by qubits described on the Bloch sphere, and then by repeatedly rotating all qubits on this individual about the same coordinate axis through random angles, some new individuals are generated. By choosing the best individual as a new vortex center, and rotating it again until meeting the termination conditions, the global optimal solution can be obtained. As the search in each dimension is carried out on the Bloch sphere, thus it is helpful to enhance the diversity of candidate solutions and inhibit premature convergence in the late stages of the algorithm. That the proposed algorithm is superior to the original one is demonstrated by the experimental results of some benchmark functions extreme optimization. [ABSTRACT FROM AUTHOR]

In this paper, we propose a quantum circuit for calculating the squared sum of the inner product of quantum states. The circuit is designed by the multi-qubits controlled-swapping gates, in which the initial state of each control qubit is | 0 〉 and they are in the equilibrium superposition state after passing through some Hadamard gates. Then, according to the control rules, each basis state in the superposition state controls the corresponding quantum states pair to swap. Finally, the Hadamard gates are applied to the control qubits again, and the squared sum of the inner product of many pairs of quantum states can be obtained simultaneously by measuring only one control qubit. We investigate the application of this method in quantum images matching on a classical computer, and the experimental results verify the correctness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, we design a quantum associative classifier, which includes pattern storage and pattern classification. For pattern storage, we present a method to construct quantum superposition states with arbitrary number of basis states. The method employs three groups of qubits to encode the sequence number, category, and value of each sample respectively. Firstly, according to the total number of samples N to be stored, the number of sequence number qubits needed by associative classifier is calculated. Then, some quantum rotation gates and Hadamard gates are used to transform the sequence number qubits with initial state of | 0 ⟩ into the quantum equilibrium superposition state which contains exactly N basis states. Finally, according to the category and value of the sample to be stored, the remaining two groups of qubits with initial state of | 0 ⟩ are converted into corresponding quantum basis states by some controlled operations. For associative classification, we design a classification method based on quantum minimum search. Firstly, the Hamming distances between the input sample and all the stored samples are calculated, and then Grover’s algorithm with fixed phase is used to search the minimum value of these Hamming distances. At this time, the category of the stored sample corresponding to the minimum value is the category of the input sample. The specific classification results can be obtained through the measurement of quantum state in the register. The number of iterations of the search is exponentially lower than that of its classical counterpart, so that pattern classification can be realized quickly. [ABSTRACT FROM AUTHOR]

This paper presented a quantum representation and some basic operations for one-dimensional finite length digital signal. For the representation, similar to the existing flexible representation of quantum audio (FRQA), two sets of qubits are used to represent the amplitudes and positions of the signal, respectively, wherein the amplitude is represented by an (n + 1)-bit signed number in twos complement, including one sign bit, m integer bits and n − m fractional bits. The basic operations include the addition, subtraction, multiplication, division, and circular convolution of two digital signals. We designed the quantum circuits that implements these basic operations, analyzed the computational complexity, and verified the correctness of these circuits by simulations on classical computers. [ABSTRACT FROM AUTHOR]

Image scaling is the basic operation that is widely used in classic image processing, including nearest-neighbor interpolation, bilinear interpolation, and bicubic interpolation. In quantum image processing (QIP), the research on image scaling is focused on nearest-neighbor interpolation, while the related research of bilinear interpolation is very rare, and that of bicubic interpolation has not been reported yet. In this study, a new method based on quantum Fourier transform (QFT) is designed for bilinear interpolation of images. Firstly, some basic functional modules are constructed, in which the new method based on QFT is adopted for the design of two core modules (i.e. addition and multiplication), and then these modules are used to design quantum circuits for the bilinear interpolation of images, including scaling-up and down. Finally, the complexity analysis of the scaling circuits based on the elementary gates is deduced. Simulation results show that the scaling image using bilinear interpolation is clearer than that using the nearest-neighbor interpolation. [ABSTRACT FROM AUTHOR]

At present, the classical least-significant-bit (LSB) based image steganography has been extended to quantum image processing. For the existing LSB-based quantum image steganography schemes, the embedding capacity is no more than 3 bits per pixel. Therefore, it is meaningful to study how to improve the embedding capacity of quantum image steganography. This work presents a novel LSB-based steganography using reflected Gray code for colored quantum images, and the embedding capacity of this scheme is up to 4 bits per pixel. In proposed scheme, the secret qubit sequence is considered as a sequence of 4-bit segments. For the four bits in each segment, the first bit is embedded in the second LSB of B channel of the cover image, and and the remaining three bits are embedded in LSB of RGB channels of each color pixel simultaneously using reflected-Gray code to determine the embedded bit from secret information. Following the transforming rule, the LSB of stego-image are not always same as the secret bits and the differences are up to almost 50%. Experimental results confirm that the proposed scheme shows good performance and outperforms the previous ones currently found in the literature in terms of embedding capacity. [ABSTRACT FROM AUTHOR]

In quantum image steganography, embedding capacity and security are two important issues. This paper presents a novel quantum steganography scheme using color images as cover images. First, the secret information is divided into 3-bit segments, and then each 3-bit segment is embedded into the LSB of one color pixel in the cover image according to its own value and using Gray code mapping rules. Extraction is the inverse of embedding. We designed the quantum circuits that implement the embedding and extracting process. The simulation results on a classical computer show that the proposed scheme outperforms several other existing schemes in terms of embedding capacity and security. [ABSTRACT FROM AUTHOR]

To address quantum description for color images, an improved FRQI model called FRQCI is proposed in this paper. In our model, the qubit has two-phase parameters and , and the primary color R is stored in , the primary colors G and B are stored in . We provide several simple image processing operators, including color change and geometric transformation. Next, we focus on an encryption algorithm, which includes two parts: position scrambling and color transformation. All operations involved in this paper are implemented by the rotation of the qubit on the Bloch sphere. The simulation results on classical computer show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper we investigate the use of quantum Fourier transform (QFT) in the field of image processing. We consider QFT-based color image filtering operations and their applications in image smoothing, sharpening, and selective filtering using quantum frequency domain filters. The underlying principle used for constructing the proposed quantum filters is to use the principle of the quantum Oracle to implement the filter function. Compared with the existing methods, our method is not only suitable for color images, but also can flexibly design the notch filters. We provide the quantum circuit that implements the filtering task and present the results of several simulation experiments on color images. The major advantages of the quantum frequency filtering lies in the exploitation of the efficient implementation of the quantum Fourier transform. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the quantum image spatial filtering, and focused on the design method of quantum weighted averaging filter and its application in image de-noising. To this end, we first designed the quantum circuits for some auxiliary modules, such as swapping two numbers, comparing two numbers, computing the weighted average of some integers, etc. Next, we constructed a weighted averaging filter of size 3 × 3 using auxiliary modules. The spatial filtering directly on the image itself can be accomplished by using designed filter. We provided the quantum circuits that implements the filtering task and presented the results of several simulation experiments on some gray images with different noises. The significance of this paper is to explore the quantum realization method of image filtering in spatial domain. [ABSTRACT FROM AUTHOR]

In this paper, a simple encryption scheme for quantum color image is proposed. Firstly, a color image is transformed into a quantum superposition state by employing NEQR (novel enhanced quantum representation), where the R,G,B values of every pixel in a 24-bit RGB true color image are represented by 24 single-qubit basic states, and each value has 8 qubits. Then, these 24 qubits are respectively transformed from a basic state into a balanced superposition state by employed the controlled rotation gates. At this time, the gray-scale values of R, G, B of every pixel are in a balanced superposition of 2 multi-qubits basic states. After measuring, the whole image is an uniform white noise, which does not provide any information. Decryption is the reverse process of encryption. The experimental results on the classical computer show that the proposed encryption scheme has better security. [ABSTRACT FROM AUTHOR]

In this paper, a novel quantum representation and watermarking scheme based on the controlled rotation of qubits are proposed. Firstly, a flexible representation for quantum color image (FRQCI) is proposed to facilitate the image processing tasks. Some basic image processing operations based on FRQCI representation are introduced. Then, a novel watermarking scheme for quantum images is presented. In our scheme, the carrier image is stored in the phase $$\theta $$ of a qubit; at the same time, the watermark image is embedded into the phase $$\phi $$ of a qubit, which will not affect the carrier image's visual effect. Before being embedded into the carrier image, the watermark image is scrambled to be seemingly meaningless using quantum circuits, which further ensures the security of the watermark image. All the operations mentioned above are implemented by the controlled rotation of qubits. The experimental results on the classical computer show that the proposed watermarking scheme has better visual quality under a higher embedding capacity and outperforms the existing schemes in the literature. [ABSTRACT FROM AUTHOR]

• Lithofacies identification based on the shape characteristics of logging response. • Lithofacies identification method of using 2-dimensional convolution network. • Lithofacies identification method of using 1-dimensional convolution network and LSTM. To address lithofacies identification of single-well, we proposed two solutions based on logging response and convolutional neural network. Firstly, the lithofacies types are obtained according to the coring well data, and then the logging response characteristics of different lithofacies are obtained by associating the lithofacies with some logging responses. Finally, the mapping relationship between logging responses and lithofacies types is established by convolutional neural network. The trained network can be used for single-well lithofacies identification. In the first scheme, we employed a deep residual network based on transfer learning. This network receives three-dimensional image as input and use two-dimensional convolution to extract pattern characteristics. Hence, it needs to plot the logging responses of each lithofacies into an image in advance. In the second scheme, we employed a parallel model composed of residual network and long short-term memory network, which can directly receive the sequence data of logging response without transforming them into images. The lithofacies identification results of 2 test single-wells show that the identification accuracy of the two schemes is more than 92 % , which provides a new way for lithofacies identification in oil and gas exploration and development. [ABSTRACT FROM AUTHOR]

Abstract: To enhance the performance of classical neural networks, a quantum-inspired neural networks model based on the controlled-Hadamard gates is proposed. In this model, the inputs are discrete sequences described by a matrix where the number of rows is equal to the number of input nodes, and the number of columns is equal to the sequence length. This model includes three layers, in which the hidden layer consists of quantum neurons, and the output layer consists of classical neurons. The quantum neuron consists of the quantum rotation gates and the multi-qubits controlled-Hadamard gates. A learning algorithm is presented in detail according to the basic principles of quantum computation. The characteristics of input sequence can be effectively obtained from both breadth and depth. The experimental results show that, when the number of input nodes is closer to the sequence length, the proposed model is obviously superior to the BP neural networks. [Copyright &y& Elsevier]

Abstract: A novel quantum-inspired evolutionary algorithm is proposed based on the Bloch coordinates of quantum bits (qubits) in this paper. The chromosome is comprised of qubits whose Bloch coordinates comprise gene chain. The quantum chromosomes are updated by quantum rotation gates, and are mutated by quantum non-gates. For the rotation direction of quantum rotation gates, a simple determining method is proposed. For the rotation and mutation of qubits, two new operators are constructed based on Bloch coordinates of qubits. In this algorithm, the Bloch coordinates of each qubit are regarded as three paratactic genes, each chromosome contains three gene chains, and each gene chain represents an optimization solution, which can accelerate the convergence process for the same number of chromosomes. By two application examples of function extremum and neural network weights optimization, the simulation results show that the approach is superior to common quantum evolutionary algorithm and simple genetic algorithm in both search capability and optimization efficiency. [Copyright &y& Elsevier]

Abstract: When the Grover''s algorithm is applied to search an unordered database, the probability of getting correct results usually decreases with the increase of marked items. The reason for this phenomenon is analyzed in this Letter, the Grover iteration is studied, and a new phase matching is proposed. With application of the new phase matching, when the fraction of marked items is greater than 1/3, the probability of getting correct results is greater than 25/27 with only one Grover iteration. The validity of the new phase matching is verified by a search example. [Copyright &y& Elsevier]

• We propose two improved Gauss-Seidel projection methods for Landau-Lifshitz equation. • We verify unconditional stability with respect to mesh size and damping parameter. • We demonstrate first-order accuracy in time and second-order accuracy in space. • We show the savings are about 2/7 and 4/7 compared to the original projection method. • We simulate magnetization dynamics with hysteresis loops and magnetization profiles. Micromagnetic simulation is an important tool to study various dynamic behaviors of magnetic order in ferromagnetic materials. The underlying model is the Landau-Lifshitz-Gilbert equation, where the magnetization dynamics is driven by the gyromagnetic torque term and the Gilbert damping term. Numerically, considerable progress has been made in the past decades. One of the most popular methods is the Gauss-Seidel projection method developed by Xiao-Ping Wang, Carlos García-Cervera, and Weinan E in 2001. It first solves a set of heat equations with constant coefficients and updates the gyromagnetic term in the Gauss-Seidel manner, and then solves another set of heat equations with constant coefficients for the damping term. Afterwards, a projection step is applied to preserve the length constraint in the pointwise sense. This method has been verified to be unconditionally stable numerically and successfully applied to study magnetization dynamics under various controls. In this paper, we present two improved Gauss-Seidel projection methods with unconditional stability. The first method updates the gyromagnetic term and the damping term simultaneously and follows by a projection step. The second method introduces two sets of approximate solutions, where we update the gyromagnetic term and the damping term simultaneously for one set of approximate solutions and apply the projection step to the other set of approximate solutions in an alternating manner. Compared to the original Gauss-Seidel projection method which has to solve heat equations 7 times at each time step, the improved methods solve heat equations 5 times and 3 times, respectively. First-order accuracy in time and second-order accuracy in space are verified by examples in both 1D and 3D. In addition, unconditional stability with respect to both the grid size and the damping parameter is confirmed numerically. Application of both methods to a realistic material is also presented with hysteresis loops and magnetization profiles. Compared with the original method, the recorded running times suggest that savings of both methods are about 2/7 and 4/7 for the same accuracy requirement, respectively. [ABSTRACT FROM AUTHOR]

Morphological image processing is a relatively mature image processing method in classical image processing. However, in quantum image processing, the related results are still quite scarce. In this paper, we first design the quantum circuits of the two basic operations of dilation and erosion for binary images and grayscale images. On this basis, for binary image, the quantum circuits of three morphological algorithms (noise removal, boundary extraction and skeleton extraction) are designed in detail. For grayscale image, the quantum circuits of three morphological algorithms (i.e., edge detection, image enhancement and texture segmentation) are also designed. In the design of these circuits, the parallelism of quantum computation is considered. The analysis of the circuits complexity shows that all the six morphological algorithms can speed up their classic counterparts. [ABSTRACT FROM AUTHOR]