Search

Quantum private comparison (QPC) is judging whether two secrets are equal or not without any information leakage. This paper suggests that the privacy is reflected in the three pieces of information—value, data length, and bits equality. However, existent QPC protocols generally just keep the first item, i.e. value secret, whereas the other two is revealed. This work insists that it should be forbidden for a true QPC protocol. For this purpose, the paper firstly proposes a novel concept of enhanced quantum private comparison (EQPC), which protects not only secrets' specific value, but also their data length and bits equality, and then presents a novel protocol implementing EQPC. The proposed EQPC protocol was fully analysed correct and secure. Also, it is extremely easy to implement for its only usage of one type of Bell states. It can be said that the EQPC protocol is a significant step forward for the QPC development. [ABSTRACT FROM AUTHOR]

Quantum-enhanced receiver is an effective approach to discriminate weak coherent states with better performance. As a typical quantum-enhanced measurement scheme, Dolinar receivers theoretically approach the standard quantum limit by using real-time quantum feedback with optimal displacement and photon measurements. However, thermal noise can interfere with the results of photon measurement, ultimately leading to a degradation of performance. In this paper, we analyze the influence of thermal noise toward the detector and we build a more practical model of quantum-enhanced receiver with a replaced photon number resolving detector under thermal noise. The calculation model for decision strategy and displacement operator is optimized correspondingly by theoretical analysis to further improve the detection performance. This scheme provides an exact number of photons and accuracy calculation model of displacement operator and decision strategy, which reduce the degradation of performance caused by thermal noise. The simulation results show that the thermal noise causes a large interference with the quantum-enhanced measurements. The corrected scheme with the measurement model developed in this paper reduces the degradation of performance caused by thermal noise, and beats the standard quantum limit with the mean photon number of thermal noise less than 0.1. This work provides a meaningful step toward the performance enhancement of coherent state discrimination and enhances the capability for practical applications of quantum-enhanced measurement in coherent optical communications. [ABSTRACT FROM AUTHOR]

The parallel computing power of quantum computing and the special properties of qubits provide an effective solution for image processing tasks. This paper presents a quantum image encryption algorithm based on Fisher–Yates algorithm and Logistic mapping. Firstly, the Fisher–Yates algorithm is used to generate three key sequences, one of which is used to encode the coordinate qubits of the image. Using the other two keys and the preset rules, the quantum coordinate scrambling operation is designed based on the encoded coordinate qubit, which effectively scrambles the spatial information of the plaintext image. Next, another set of key sequences is generated, one of which is used to encode the color qubits of the image. Using two other key sequences and different rules, a qubit plane scrambling operation based on coded color qubits is designed, and the color information of image is scrambled successfully. Finally, the quantum key image is generated based on Logistic mapping, and the key image is scrambled based on Fisher–Yates algorithm to improve the key complexity. The final ciphertext image is obtained by performing XOR operation between the original image and the scrambled key image. The complete quantum circuit diagram of the scheme is given in this paper. The experimental results and security analysis prove the effectiveness of the scheme, which provides a large key space and the computational complexity is only O(n). [ABSTRACT FROM AUTHOR]

Internet of vehicles (IoV) technology connects various types of vehicles through the Internet of Things to achieve mutual communication and data sharing, thereby promoting the development of intelligent transportation systems. Present data sharing in IoV mainly relies on complicated centralized certificate management and modern public-key cryptosystems, which are insecure and inefficient because the rapid development of quantum computing has put the security of modern public-key cryptosystems under serious threat. Considering the potential quantum adversaries, this paper proposes a quantum blockchain-based data sharing scheme called quantum blockchain for IoV (QBIoV) to realize secure and efficient data sharing in IoV. Specifically, QBIoV discards vulnerable modern cryptographic components, such as classical hash functions, public key signatures, and voting protocols, and innovatively introduces quantum replacement items, such as a quantum hash function (QHF), a quantum public key signature, and a quantum binary voting (QBV) protocol, to eliminate potential quantum cyberspace attack hazards. Furthermore, QBIoV improves the conventional proof of authority (PoA) consensus algorithm and introduces a more secure and fair consensus mechanism called quantum proof of authority (QPoA). QPoA enhances the efficiency of the blockchain system, enabling the secure and efficient sharing of data in IoV. Additionally, a security analysis of QBIoV is conducted, demonstrating that QBIoV is secure against both classic and quantum adversaries, with performance comparisons proving that QBIoV outperforms peer work regarding resource efficiency. In conclusion, this paper provides an effective solution for enhancing data security protection in IoV, assisting in designing blockchain systems in the post-quantum era. [ABSTRACT FROM AUTHOR]

Quantum machine learning (QML) has emerged as a promising domain offering significant computational advantages over classical counterparts. In recent times, researchers have directed their attention towards this field. The objective of this paper is to provide a thorough overview of the advancements in quantum machine learning, encompassing the state-of-the-art approaches. The machine learning field is itself quite diverse. Diversity of QML is broadened due to the respective roles the quantum information processing and machine learning play in it. The study focuses on analysing the predictive efficacy of deep learning models on time series data. After experimental evaluation, we have chosen deep learning models that have better performance on time series data. The paper illustrates how different quantum techniques such as quantum encoding, optimization, etc., are used in quantum-enhanced models and provides a comprehensive review and an experimental analysis of three state-of-the-art quantum-enhanced models. Mental health is a serious global public health concern that has permeated modern civilization. So, seven time series data related to mental health conditions were collected from SWELL-KW, Wesad and psykose. Based on the experimental findings from the current dataset, it is evident that the quantum LSTM model exhibits superior predictive performance compared to other state-of-the-art approaches. [ABSTRACT FROM AUTHOR]

The foundation of this research is the quantum implementation of two hashing algorithms, namely Secure Hash Algorithm (SHA1) and Message Digest (MD5). Quantum cryptography is a challenging topic in network security for future networks. Quantum cryptography is an outgrowth of two broad topics—cryptology and cryptanalysis. In this paper, SHA1 and MD5 algorithms are designed and implemented for quantum computers. The main aim is to study and investigate the time requirement to build a hash and the bit rate at which a hash value is sent through. In this paper, a comprehensive analysis of these two algorithms is performed. Experiments have been done to compare and contrast the performances of the classical and proposed algorithms. In the experiment, it was found that the total time of execution of quantum SHA1 and quantum MD5 is much higher than the classical SHA1 and MD5. During quantum MD5 execution, it is observed that the time doubles when the number of chunks is increased from 1 to 2. Another experimental observation is that the execution time of the implemented algorithms depends upon the processor's speed. [ABSTRACT FROM AUTHOR]

Thus far, several papers reported concrete resource estimates of Shor's quantum algorithm for solving the elliptic curve discrete logarithm problem. In this paper, we study quantum FLT-based inversion algorithms over binary elliptic curves. There are two major algorithms proposed by Banegas et al. and Putranto et al., where the former and latter algorithms achieve fewer numbers of qubits and smaller depths of circuits, respectively. We propose two quantum FLT-based inversion algorithms that essentially outperform previous FLT-based algorithms and compare the performance for NIST curves of the degree n. Specifically, for all n, our first algorithm achieves fewer qubits than Putranto et al.'s one without sacrificing the number of Toffoli gates and the depth of circuits, while our second algorithm achieves smaller depths of circuits without sacrificing the number of qubits and Toffoli gates. For example, when n = 571 , the number of qubits of our first algorithm is 74 % of that of Putranto et al.'s one, while the depth of our second algorithm is 83 % of that of Banegas et al.'s one. The improvements stem from the fact that FLT-based inversions can be performed with arbitrary sequences of addition chains for n - 1 although both Banegas et al. and Putranto et al. follow fixed sequences that were introduced by Itoh and Tsujii's classical FLT-based inversion. In particular, we analyze how several properties of addition chains, which do not affect the computational resources of classical FLT-based inversions, affect the computational resources of quantum FLT-based inversions and find appropriate sequences. [ABSTRACT FROM AUTHOR]

Combining the advantages of quantum computing and machine learning, quantum machine learning is anticipated to advance the field of artificial intelligence further. Recent research has demonstrated, however, that the state-of-the-art quantum classifiers can be deceived by adversarial examples, leading to incorrect classifications by quantum models. This paper proposes the quantum fuzzy convolutional neural network, which is used to detect adversarial examples, by combining the benefits of fuzzy systems and the quantum convolutional neural network. This defensive strategy does not modify the structure and training process of the quantum classifier that requires protection. Simulation experiments show that the adversarial example detection approach proposed in this paper can successfully separate the real data distribution from the adversarial data distribution and detect the adversarial examples generated by a specific attack method on a specific quantum classifier. [ABSTRACT FROM AUTHOR]

This paper presents a quantum image steganography algorithm based on HSI color space embedding technique. To increase the security of sensitive information, a three-dimensional hyperchaotic system incorporating sinusoidal mapping, Henon mapping, and Cubic mapping using the cascade modulation method is first presented. Additionally, a brand-new steganography algorithm built on the HSI color space embedding method is suggested in this study. The effective pixel information of three channels can be concentrated in one intensity channel by converting color images from RGB to HSI, which decreases the null domain steganography algorithm's time and space complexity. In the meantime, a successful quantum steganography circuit is created. The simulation and numerical analysis results show that the algorithm has good invisibility, security, and robustness. [ABSTRACT FROM AUTHOR]

Quantum computing algorithms offer the potential to revolutionize computational efficiency across a wide range of applications. However, one significant challenge that has impeded progress in color image processing is the difficulty of representing color relationships in quantum computers. In addition to this challenge, another major hurdle is efficiently representing data in quantum computers and performing quantum operations or arithmetic. To overcome these challenges, researchers have proposed various novel approaches, including using qubit lattices and flexible representations of quantum images. Despite these advancements, the quantum color image processing field is still in its early stages. This paper proposes a new arithmetic for processing quantum color images using novel operations for 2-qubits and the concept of quantum quaternion Fourier transform. We first study arithmetic operations in the 2-qubit setting, such as multiplication, inverse, and division on 2-qubits in quantum computation. The space of 2-qubits with real amplitudes is considered, and prototypes of power and exponent operations are also defined. The presented operations are applied to quantum superpositions of 2-qubits, to enable processing of quaternion images, which are 4-dimensional vectors and can be represented by 2-qubits at each pixel. The proposed methods and tools are designed to be embedded in a quantum device, which allows them to be used in various applications in the 2-qubits domain. To facilitate practical applications, the paper also introduces a tool for processing color images that can be used for color image filtering. Furthermore, this work provides a foundation to explore theoretical and practical aspects of color image processing on quantum computers. [ABSTRACT FROM AUTHOR]

Quantum secret sharing is one of the important techniques in quantum cryptography. In this paper, we propose a novel dynamic hierarchical quantum secret sharing scheme with general access structure. Participants from different levels share the same secret. Firstly, a special hierarchical structure based on the generalized GHZ state is constructed, which expands the application value of the existing hierarchical quantum secret sharing. Secondly, this paper uses the monotone span program (MSP) and the generalized Pauli operator to realize the dynamic property of the scheme, which includes three aspects: The hierarchical access structure is variable; participants can join or leave, and the shared secret can be updated. Moreover, the shares of the participants can be protected so as to reduce communication consumption due to reuse of the shares. Finally, compared with other hierarchical quantum secret sharing schemes, the proposed scheme is not only more flexible but also more secure. [ABSTRACT FROM AUTHOR]

Corners are very important local features for an image that can be widely used in many image processing tasks such as object detection, image recognition and data compression. However, current corner detection algorithms are complex and time consuming. In this paper, a new quantum fast corner detection algorithm is proposed taking full advantage of quantum parallelism. The algorithm is implemented in three steps: the 'nucleus' is defined and its neighborhood pixels are determined in the first step. Two thresholds are selected in the second step, and corners are obtained in the third step. The first and second steps are the same as the classical corner detection algorithm. The third step is divided into two stages. In the first stage, the differences between grayscale values of the nucleus and pixels in the neighborhood are calculated, followed by the comparison of those differences with the 'intensity threshold,' then is the quantum measurement on the comparison results, and finally the measured results are organized into an array. In the second stage, the array is used for counting, followed by the comparison of those counted results with the 'accuracy threshold,' and finally the corners are obtained. It is worth noting that through the quantum–classical–quantum mode, quantum resources can be reduced significantly. The analysis in the proposed quantum fast corner detection algorithm shows that the time complexity and quantum delay of the algorithm do not increase with the increase in the size and number of images, and its time complexity is exponentially lower than that of the classical fast corner detection algorithm. [ABSTRACT FROM AUTHOR]

This paper investigates quantum error correction schemes for fully-correlated noise channels on an n-qubit system, where error operators take the form W ⊗ n , with W being an arbitrary 2 × 2 unitary operator. In previous literature, a recursive quantum error correction scheme can be used to protect k qubits using (k + 1) -qubit ancilla. We implement this scheme on 3-qubit and 5-qubit channels using the IBM quantum computers, where we uncover an error in the previous paper related to the decomposition of the encoding/decoding operator into elementary quantum gates. Here, we present a modified encoding/decoding operator that can be efficiently decomposed into (a) standard gates available in the qiskit library and (b) basic gates comprised of single-qubit gates and CNOT gates. Since IBM quantum computers perform relatively better with fewer basic gates, a more efficient decomposition gives more accurate results. Our experiments highlight the importance of an efficient decomposition for the encoding/decoding operators and demonstrate the effectiveness of our proposed schemes in correcting quantum errors. Furthermore, we explore a special type of channel with error operators of the form σ x ⊗ n , σ y ⊗ n and σ z ⊗ n , where σ x , σ y , σ z are the Pauli matrices. For these channels, we implement a hybrid quantum error correction scheme that protects both quantum and classical information using IBM's quantum computers. We conduct experiments for n = 3 , 4 , 5 and show significant improvements compared to recent work. [ABSTRACT FROM AUTHOR]

In this paper, we prove the unconditional security of a single-state circular mediated semi-quantum key distribution protocol. It starts with a third-party quantum server, TP, sending a string of qubits sequentially through two classical users Alice and Bob, and finally back to TP. We derive an expression for the key rate in the asymptotic scenario. When the communication parties Alice and Bob observe that the error rate is less than a determined threshold, the key rate is always greater than 0, so they can distill a string of secure secret keys. At the end of this paper, we extend this protocol to the multiple users case, where more than two classical users establish a string of security keys. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the learnability of some hypothesis sets for regression and binary classification defined by quantum circuits. The analysis is based on concepts and results from quantum computing (Solovay–Kitaev theorem) and statistical learning theory (covering numbers and Rademacher complexity). The obtained learning bounds depend polynomially on the parameters defining the circuits set, namely the number of qubits and the number of 1 and 2 qubits gates used for their implementation. Our setting is quite general: no realisability assumptions are made, and any 1 and 2 qubits gates are allowed. Finally, we compare the current bounds with others found in the literature and discuss their implications for classification and regression on quantum data. [ABSTRACT FROM AUTHOR]

This paper proposes a novel quantum color image steganography algorithm using an efficient embedding technique of exploiting modification direction (EMD). In this paper, the EMD algorithm is improved to reduce the number of modified pixels and smooth the noticeable changes at both ends of the histogram of hidden images. Besides, a fractional-order chaotic system is proposed to increase the security of secret information. The effective quantum circuit for the quantum steganography algorithm is also presented in this paper. The simulation and numerical analysis demonstrate that the proposed algorithm has good performance in imperceptibility analysis, capacity analysis and security analysis. [ABSTRACT FROM AUTHOR]

This paper takes advantage of the quantum mechanics to present two efficient circular controlled quantum communication schemes. The proposed protocols utilize ten qubits for transmitting the information qubits to five partners circularly, under the permission of a controller. The first protocol is a circular controlled quantum teleportation, which teleports unknown quantum states. The second protocol is a circular controlled quantum broadcast scheme which sends quantum states to two dispersed recipients, circularly. In this paper, the effects of quantum noises on these protocols are analyzed, and the fidelity of the quantum states is calculated too. We will see that, in the circular controlled quantum teleportation protocol, the impact of the noise on input qubits is less than its impact on channel qubits. [ABSTRACT FROM AUTHOR]

Qutrit is a three-level quantum system with a higher level than qubits, which can process quantum information in a more complex state space. Therefore, in some information processing tasks, qutrits are more efficient than qubits. In this paper, we first briefly review the basic knowledge of qubit and extend it to the qutrit scenario. Then, the noiseless qutrit channel is given by simple extension, and the transmission characteristics between it and the noiseless qubit channel are discussed. Subsequently, we provided a three-dimensional version of the amplitude damping channel based on its construction method. In this paper we will refer to it as the noisy qutrit channel N (ρ) . Finally, we discuss the transmission characteristics of N (ρ) and the amplitude damping channel, as well as the expected fidelity and entanglement fidelity of N (ρ) . What's interesting is that we find whether it is a noisy channel or a noiseless channel, the qutrit channel can send qubit information, but the qubit channel cannot send qutrit information completely. The special case in which the qubit channel can send qutrit information completely is when the input qutrit state is | 0 ⟩ or | 1 ⟩ or a linear combination of | 0 ⟩ and | 1 ⟩ . [ABSTRACT FROM AUTHOR]

This paper is a fundamental exploration of quantum theory within the quadratic Fock space in consistency with the quadratic quantization program, with a particular focus on two sets of operators that hold immense significance: the quadratic creation and preservation operators. In this paper, we highlight a critical contribution to the quadratic quantization program. In which we prove that when the argument f is a real valued function, the quadratic preservation operator is symmetric and even essentially self-adjoint. This mathematical confirmation not only solidifies the foundations of quantum theory but also amplifies its practical applicability in real-world scenarios. In consistency with previous result, we give the exponential action of the creation operator on the domain of quadratic exponential vectors. This is an expansion of what obtained in Accardi, Ouerdiane, Rebei (Infin Dimens Anal Quantum Probab Relat Top 13(4):551–587, 2010) for the one-mode case. [ABSTRACT FROM AUTHOR]

Quantum secret sharing plays a crucial role in quantum cryptography. In this paper, we present a rational hierarchical (t,n)-threshold quantum secret sharing scheme based on Lagrange interpolation. In our scheme, participants possess rational and hierarchical properties, and the secret can be reconstructed when the number of rational participants satisfies the hierarchical (t,n)-threshold structure proposed in this paper. The reconstructed secret can encompass both classical information and quantum state information, enhancing the practicality and flexibility of our scheme compared to existing ones. Additionally, we redefine the utility of participants based on their roles in the secret recovery process. This newly defined utility allows for a more precise analysis of the correctness, fairness, and equilibrium of our scheme. Finally, our scheme not only resists a typical set of external attacks but also incorporates mechanisms to detect forgery and collusion among participants. [ABSTRACT FROM AUTHOR]

In this paper, we present a construction of quantum error-correcting codes (QECCs) codes and entanglement-assisted quantum error-correcting (EAQECCs) using Euclidean hulls and sums of cyclic codes of length n over a family of ring R s = F q + v 1 F q + v 2 F q + ⋯ + v s F q , where q is an odd prime power and v i 2 = v i , v i v j = v j v i = 0 , for i , j = 1 , 2 , 3 , ⋯ , s and i ≠ j . The study delves into various aspects of this construction. We explore the generator polynomials, the dimension of both Euclidean hulls and the sums of cyclic codes over the ring R s . Further, we determine several new QECCs and EAQECCs. This paper claims that our obtained codes have improved parameters (e.g. higher minimum distance or greater dimension) than the existing quantum codes. Moreover, we present some detailed examples that effectively illustrate our findings. [ABSTRACT FROM AUTHOR]

Finding solutions to systems of linear equations is a common problem in many areas of science and engineering, with much potential for a speed up on quantum devices. While the Harrow–Hassidim–Lloyd (HHL) quantum algorithm yields up to an exponential speed up over classical algorithms in some cases, it requires a fault-tolerant quantum computer, which is unlikely to be available in the near-term. Thus, attention has turned to the investigation of quantum algorithms for noisy intermediate-scale quantum (NISQ) devices where several near-term approaches to solving systems of linear equations have been proposed. This paper focuses on the Variational Quantum Linear Solvers (VQLS), and other closely related methods and adaptions. Several contributions are made in this paper, which include: the first application of the Evolutionary Ansatz to the VQLS (EAVQLS), the first implementation of the Logical Ansatz VQLS (LAVQLS), based on the Classical Combination of Quantum States (CQS) method, a proof of principle demonstration of the CQS method on real quantum hardware and a method for the implementation of the Adiabatic Ansatz on the VQLS (AAVQLS). These approaches are implemented and contrasted. The CQS method is run with moderate success on a real quantum device. The EAVQLS and AAVQLS show promise as possible improvements to the standard VQLS algorithm once refined. [ABSTRACT FROM AUTHOR]

The size of quantum circuits is growing as quantum computing develops, yet the devices available today cannot handle the large-scale quantum computing problems. Distributed quantum computing is an effective way to solve this problem. How to efficiently reduce the transmission cost of distributed quantum circuits is crucial because it serves as a fundamental standard of the effectiveness of distributed quantum computing. To this end, this research suggests a distributed storage pattern and a merged transfer model. Based on this distributed storage pattern, the quantum circuit matches the appropriate architecture for distribution, and the circuit is initially partitioned. To determine the most effective partitioning scheme for the circuits, a genetic algorithm is employed to reorder qubits and partition distributed circuits. Based on the merged transfer model, the exchange rules of quantum gates are used to combine a number of discontinuous gates into a single transmission through which these gates can be executed. The merged transfer model completes execution with fewer redundant transmissions, so as to achieve a lower transmission cost overall. The method proposed in this paper takes up fewer quantum resources and has a lower transmission cost than previous research results, with an average transmission cost optimization of 51.3%. [ABSTRACT FROM AUTHOR]

Designing quantum arithmetic logic unit, quantum full adder and quantum full subtractor are the most vital digital circuits. The paper first presents the fundamentals of reversible quantum computing and quantum implementation design methodology with matrix modeling approach of realization of controlled gates. For any designer, it is challenging to reduce the controlled-gate count in circuit implementation. Based on the available 3 × 3 reversible quantum gates, the optimized quantum implementations of five novel and efficient controlled adders/subtractors are presented. Significant improvements in all the performance parameters have been achieved. Moreover, optimized quantum cost improvement of 20%, 16%, 9%, 10% and 31.25% has been obtained. The paper makes comparison of adder/subtractor circuits for efficient quantum realization. It has been deducted that our proposed designs are combined in nature and are more efficient than existing separate adder/subtractor and combined designs. [ABSTRACT FROM AUTHOR]

To minimize the quantum resources consumed by the quantum channel and the classical resources consumed in the communication process, this paper proposes bidirectional quantum teleportation using a five-qubit cluster state as the quantum channel. Alice sends her message, a pure entangled-state EPR pair, to the receiver, Bob. Bob also sends his message, a single quantum state, to Alice, so that both parties can successfully complete the asymmetric quantum teleportation process. A local-based controlled-NOT gate (CNOT gate) operation is used to transform the five-qubit cluster state into a different state from the past. According to the GHZ state measurement, the Bell state measurement, and the corresponding unitary transformation, the communication parties can complete the asymmetric quantum teleportation process. Because this paper does not involve third-party controllers, it reduces resource consumption and operational complexity and optimizes transmission efficiency. [ABSTRACT FROM AUTHOR]

Introduction: In the future, quantum networks will be an important development direction. Quantum networks should be studied considering quantum's unique physical properties. In quantum networks with limited resources, decoherence will lead to qubits loss, which restricts the time that data qubits can be stored in memory before use. To realize the network function, it is very important to transmit data qubits as quickly as possible. In order to ensure timeliness and make use of entanglement resources as much as possible, this paper proposes a concurrent multipath entanglement routing scheme based on segment routing for quantum hybrid networks. Methods: In this scheme, centralized routing is used to calculate the "segments" of quantum relay path, and distributed routing is used to transmit control messages between the "segments". The "concurrent" mechanism is fully adopted in classical messages passing, path nodes BSM (Bell State Measurement) execution and multipath shunt transmission. Conclusion: This scheme has obvious advantages in multipath concurrent transmission, traffic diversion, reducing transmission time and providing redundancy. [ABSTRACT FROM AUTHOR]

Quantum computing allows a significant speed-up over traditional CPU- and GPU-based algorithms when applied to particular mathematical challenges such as optimisation and simulation. Despite promising advances and extensive research in hard- and software developments, currently available quantum systems are still largely limited in their capability. In line with this, practical applications in quantitative finance are still in their infancy. This paper analyses requirements and concrete approaches for the application to risk management in a financial institution. On the examples of Value-at-Risk for market risk and Potential Future Exposure for counterparty credit risk, the main contribution lies in going beyond textbook illustrations and instead exploring must-have model features and their quantum implementations. While conceptual solutions and small-scale circuits are feasible at this stage, the leap needed for real-life applications is still significant. In order to build a usable risk measurement system, the hardware capacity—measured in number of qubits—would need to increase by several magnitudes from their current value of about 10 2 . Quantum noise poses an additional challenge, and research into its control and mitigation would need to advance in order to render risk measurement applications deployable in practice. Overall, given the maturity of established classical simulation-based approaches that allow risk computations in reasonable time and with sufficient accuracy, the business case for a move to quantum solutions is not very strong at this point. [ABSTRACT FROM AUTHOR]

Training of Quantum Neural Networks can be affected by barren plateaus—flat areas in the landscape of the cost function, which impede the model optimisation. While there exist methods of dealing with barren plateaus, they could reduce the model's effective dimension—the measure of its capacity to learn. This paper therefore reports an investigation of four barren plateaus countermeasures, i.e. restricting the model's circuit depth and relying on the local cost function; layer-by-layer circuit pre-training; relying on the circuit block structure to support its initialisation; as well as, model creation without any constraints. Several experiments were conducted to analyse the impact of each countermeasure on the model training, its subsequent ability to generalise and its effective dimension. The results reveal which of the approaches enhances or impedes the quantum model's capacity to learn, which gives more predictable learning outcomes, and which is more sensitive to training data. Finally, the paper provides some recommendations on how to utilise the effective dimension measurements to assist quantum model development. [ABSTRACT FROM AUTHOR]

In this paper, we study a class of Hermitian dual-containing constacyclic codes of length n = q 2 m - 1 q + 1 , where q is a power of 2 and m ≥ 2 is an integer. We apply the Hermitian construction to gain quantum constacyclic codes, and lots of codes obtained in the present paper have parameters better than those of the known quantum codes. The Hermitian hull of a linear code is defined to be the intersection of itself and its Hermitian dual. We construct a family of entanglement-assisted quantum error-correcting (EAQEC) codes with n = 4 m - 1 3 via determining the dimensions of the Hermitian Hulls. [ABSTRACT FROM AUTHOR]

A recent paper (Quantum Info. Process 16.9, 2017) proposes a classical framework named Quantum Simulation Logic (QSL) capable of an efficient classical simulation of Deutsch–Jozsa and Simon algorithms. In this comment, we show instances of the Deutsch–Jozsa (DJ) and the Simon quantum algorithms that generate incorrect results with the QSL version, contradicting the proposal and the main results of the original paper. [ABSTRACT FROM AUTHOR]

Quantum secret sharing is a way to share secret messages among several people using the quantum channel with unconditional security. Hillery et al. (Phys Rev A 59(3):1829, 1999) proposed the first quantum secret sharing protocol for three parties by using the 3-qubit GHZ states and a possible generalization of the protocol for four parties by using the 4-qubit GHZ states. Also in the same paper, they proposed a three-party secret-sharing scheme to share quantum states. Later Xiao et al. (Phys Rev A 69(5):052307, 2004) generalized the quantum secret sharing protocol for n parties to share a classical secret message. In this paper, we implement these protocols in IBM simulators as well as real backends and check security against some quantum attacks. Also, we create a noise model and simulate the protocols using the noise model. Finally, we use the zero noise extrapolation method to mitigate errors due to noise. [ABSTRACT FROM AUTHOR]

Studies on conservation of quantum symmetries have been initiated by recent papers (Brannan et al. in Commun Math Phys 376(2):795–839, 2020; Lee et al. in Quantum channels with quantum group symmetry, 2020). We, in this paper, investigate how quantum symmetries can be applied to study additivity questions for covariant quantum channels, particularly for the so-called O N + -Temperley–Lieb channels. Their information-theoretic properties were analyzed in Brannan et al. (Commun Math Phys 376(2):795–839, 2020), but the associated additivity questions remained open due to highly nontrivial structures. We present a new approach to analyze O N + -Temperley–Lieb channels with small perturbations in terms of Bures distance within the asymptotic regime N → ∞ and apply continuity bounds of classical capacity, private classical capacity and quantum capacity to study strong additivity questions. [ABSTRACT FROM AUTHOR]

As one of the primitive operations of quantum cryptography, quantum secure multiparty multiplication plays an important role in practical applications. In this paper, we propose a (k, n)-threshold dynamic quantum secure multiparty multiplication protocol. (i) Based on Shamir's threshold scheme, the threshold (k, n) can be implemented; (ii) In the multiparty multiplication phase, the cheating behavior of participants can be detected by the one-to-one correspondence of hash values; (iii) Any m participants can dynamically join or exit during the execution of the protocol. Moreover, the method of this paper can also achieve dynamic quantum secure multiparty summation. Further, the security analysis shows that our protocol is resistant to intercept-resend attack, entangle-measure attack, Trojan horse attack, and participant attack. [ABSTRACT FROM AUTHOR]

In this paper, we construct stronger lower bounds for the variance-based uncertainty relations of two unitary operators, via the power-mean inequalities. It is proved that these bounds are tighter in any interval, compared to the bounds given by Bong et al. (Phys Rev Lett 120:230402, 2018) and by Yu et al. (Phys Rev A 100:022116, 2019). Moreover, we build descending sequences of lower bounds for the uncertainty relations of two or three unitary operators. For illustration, some explicit examples are given to show the tightness of our bounds, in both pure and mixed state cases. [ABSTRACT FROM AUTHOR]

The (standard) average mixing matrix of a continuous-time quantum walk is computed by taking the expected value of the mixing matrices of the walk under the uniform sampling distribution on the real line. In this paper, we consider alternative probability distributions, either discrete or continuous, and first we show that several algebraic properties that hold for the average mixing matrix still stand for this more general setting. Then, we provide examples of graphs and choices of distributions where the average mixing matrix behaves in an unexpected way: for instance, we show that there are probability distributions for which the average mixing matrices of the paths on three or four vertices have constant entries, opening a significant line of investigation about how to use classical probability distributions to sample quantum walks and obtain desired quantum effects. We present results connecting the trace of the average mixing matrix and quantum walk properties, and we show that the Gram matrix of average states is the average mixing matrix of a certain related distribution. Throughout the text, we employ concepts of classical probability theory not usually seen in texts about quantum walks. [ABSTRACT FROM AUTHOR]

Quantum error-correcting codes and entanglement-assisted quantum error-correcting codes have important applications in quantum computing and quantum communication. In this paper, we construct several classes of quantum MDS codes and entanglement-assisted quantum MDS codes by using generalized Reed-Solomon codes. The parameters of most of the codes constructed are new. [ABSTRACT FROM AUTHOR]

In this paper, we provide a method to construct quantum codes from matrix-product codes which the constituent codes have no restrictions. Then, we construct several classes of quantum codes. Some of our quantum codes are new in the sense that the parameters are different from all the previous constructions. In addition, we have that the lengths of some quantum codes are same from the previous constructions, but these quantum codes have larger dimensions. [ABSTRACT FROM AUTHOR]

Quantum computation models have profoundly impacted cryptanalysis. Differential cryptanalysis is one of the most fundamental methods in cryptanalysis of block ciphers, and one of the variations of this attack is related-key differential cryptanalysis. In this paper, quantum related-key differential cryptanalysis is implemented in two main stages of classical version. We employ Bernstein–Vazirani algorithm to find related-key differential characteristics in the first stage. Building on this basis, the second stage combines quantum maximum algorithm and quantum counting algorithm to recover correct key pair by quantum random access memory model. Compared to classical related-key differential cryptanalysis, the first stage achieves exponential acceleration, while the second stage accelerates at O(K), where K 2 represents the number of candidate key pairs. [ABSTRACT FROM AUTHOR]