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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]

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]

In quantum key distribution, secret randomness is extracted quantum-mechanically from two-sided local random choices of measurement bases. Subsequently, the public announcement of basis information is necessary to perform a security check and establish the key. Recent studies have demonstrated that, provided the basis information is accessible, even adversaries with limited computational power can readily compromise the key through side-channel attacks. In this paper, we propose a quantum key distribution scheme using entangled coherent states. The present scheme is based on the secure exchange of one-sided quantum randomness, thus obviating the necessity for basis-information announcement. This effectively closes the security loophole associated with access to basis information during side-channel attacks. The security of the present protocol has been verified against both local and global quantum attacks. Furthermore, the impact of high photon loss and an authentication scheme has been discussed. [ABSTRACT FROM AUTHOR]

In this paper, we propose a protocol for quantum secure multiparty summation and privacy sorting based on inverse quantum Fourier transform. The protocol allows multiple participants to obtain the summation and sorting of their secrets without revealing their private inputs. Each participant in the protocol encodes his/her own secret input into the phase of the d-level entangled state of n particles by means of a phase transformation operator and an inverse quantum Fourier transform. Finally, all participants perform measurements and jointly calculate the sum of all the secret data, meanwhile deriving their own rankings of the private inputs based on the final results. Compared to the existing similar quantum summation and sorting protocols, this protocol requires only a one-time particle transmission and does not require private key sequences to encrypt secret information, resulting in higher quantum efficiency. The participants can further obtain the ranking of their secret inputs by themselves. The credibility of the protocol is demonstrated in security analysis and simulation. [ABSTRACT FROM AUTHOR]

This paper proposes a magnetic field measurement scheme based on a hybrid microwave optomechanical-magnetic coupled system. The proposed sensor comprises a yttrium iron garnet sphere and an optomechanical cavity, where the spring coefficient of the cavity is parametrically modulated. The results demonstrate that the system's response to the input signal is significantly enhanced, amplifying the weak input signal while reducing the added noise of measurement below the standard quantum limit. Consequently, this hybrid system serves as an effective amplifier, generating a stronger output signal while maintaining sensitivity nearly identical to that of the bare system. We posit that these findings may offer an efficient method for magnetic field measurement and contribute to the advancement of technology in quantum precision measurements. [ABSTRACT FROM AUTHOR]

Bell state measurement plays a pivotal role in the realm of quantum communication, yet a definitive solution for achieving complete Bell state measurement remains unclear. In this paper, we propose a theoretical scheme for four-dimensional orbital angular momentum Bell state measurement, harnessing the polarization and frequency degree of freedom as auxiliary tools. Within this scheme, the input state traverses a hyperentangled state analyzer comprised of quantum logic gates, ultimately enabling the realization of Bell state measurement in a four-dimensional mode. Simultaneously, serving as a novel avenue to enhance the capacity of quantum communication, this scheme has potential applications in realizing large-capacity quantum communication. [ABSTRACT FROM AUTHOR]

Quantum key distribution (QKD) is a secure communication method that relies on the inherent randomness of quantum mechanics to ensure information-theoretic security. The first and most widely used QKD protocol is BB84, and the proof of BB84's security is vital. The discrete phase randomized BB84 protocol is a variant of the decoy BB84 protocol. It has been proven to be promising in the development of high-speed QKD systems. However, it still lacks an analysis with a finite number of pulses. This paper presents a comprehensive security analysis of the discrete phase BB84 protocol, using two different methods under different conditions. The analysis involves simulations and optimizations to determine the optimal parameter settings. It is confirmed that for a small number of finite pulses, i.e., 10 7 , if the number of discrete phases exceeds 30, one can calculate the key rate by assuming that a continuous phase randomization process was in operation. On the other hand, for a relatively smaller number of discrete values, i.e., 16 discrete phases, we have developed a numerical method to calculate the key rate. We have confirmed that its performance is reduced but still acceptable with a finite number of pulses. [ABSTRACT FROM AUTHOR]

This paper presents a study on the structure of 1-generator quasi-cyclic (QC) codes over the non-chain ring R = F q + u F q + v F q + u v F q , where u 2 = v 2 = 0 , u v = v u , and F q is a finite field of cardinality q = p r ; p is a prime. A minimal spanning set and size of these codes are determined. A sufficient condition for 1-generator QC codes over R to be free is given. BCH-type bounds on the minimum distance of free QC codes over R are also presented. Some optimal linear codes over F q are obtained as the Gray images of quasi-cyclic codes over R. Some characterizations of the Gray images of QC codes over R in F q and F q + u F q (u 2 = 0) are done. As an application, we consider self-orthogonal subcodes of the Gray images of QC codes over R to obtain new and better quantum codes than those are available in the literature. [ABSTRACT FROM AUTHOR]

Quantum computing has the potential to solve many complex algorithms in the domains of optimization, arithmetics, structural search, financial risk analysis, machine learning, image processing, and others. Quantum circuits built to implement these algorithms usually require multi-controlled gates as fundamental building blocks, where the multi-controlled Toffoli stands out as the primary example. For implementation in quantum hardware, these gates should be decomposed into many elementary gates, which results in a large depth of the final quantum circuit. However, even moderately deep quantum circuits have low fidelity due to decoherence effects and, thus, may return an almost perfectly uniform distribution of the output results. This paper proposes a different approach for efficient cost multi-controlled gates implementation using the quantum Fourier transform. We show how the depth of the circuit can be significantly reduced using only a few ancilla qubits, making our approach viable for application to noisy intermediate-scale quantum computers. This quantum arithmetic-based approach can be efficiently used to implement many complex quantum gates. [ABSTRACT FROM AUTHOR]

As one of the most important branches of quantum information science, quantum communication is known for its unconditional security and efficiency. Nevertheless, the practical security of quantum key distribution protocols and quantum secure direct communication protocols is challenged due to the imperfections in experimental devices. Despite significant progress in theoretical and experimental research on the MDI-QSDC Protocol, challenges and unresolved issues remain. For example, further enhancing the scalability and system complexity of the protocol to meet the demands of large-scale quantum networks is necessary. In this paper, we propose a multi-party MDI-QSDC scheme based on multi-degree-of-freedom hyperentangled photons. Compared to the original MDI-QSDC protocol, our protocol allows multiple parties to participate in the information transmission process. For example, for four communicating parties, we can encode the information of three independent degrees of freedom so that each photon of each degree of freedom can transmit 2 bits of information. Moreover, all measurement tasks are performed by the fifth party, which can be untrusted or even completely controlled by eavesdroppers. The protocol is resistant to all possible attacks from imperfect measurement devices. It can eventually be extended to arbitrary degrees of freedom, allowing multiple parties to participate. [ABSTRACT FROM AUTHOR]

In this paper, we first study the maximally commutative set in prime dimensional systems, which is a set of generalized Pauli matrices, and it can be used to detect the local discrimination of generalized Bell states. We give a simple characterization of prime dimensional maximally commutative sets, that is, a subset of a set of generalized Bell states, whose second subscript is a multiple of the first subscript. Furthermore, some sets of generalized Bell states which can be locally distinguishable by one-way local operation and classical communication (LOCC) are constructed by using the structural characteristics of prime dimensional maximally commutative sets. Based on these distinguishable generalized Bell states, we propose a (t, n)-threshold quantum secret sharing scheme. Compared with the existing quantum secret sharing scheme, it can be found that there are enough distinguishable states to encode classical information in our scheme, the dealer only needs to send entangled particles once to make the participants get their secret share, which makes the secret sharing process more efficient than the existing schemes. Finally, we prove that this protocol is secure under dishonest participant attack, interception-and-resend attack and entangle-and-measure attack. [ABSTRACT FROM AUTHOR]

With the development of computer vision and digital image processing technology, image segmentation has become an important part of various image processing and image analysis. Since interactive segmentation can obtain more accurate results than automatic segmentation, the most representative Graph Cuts has gradually become a popular method in image segmentation. However, this algorithm has two significant disadvantages. On the one hand, if the background is complex or very similar to the foreground, the accuracy will be low; on the other hand, the algorithm is slow and the iteration process is complicated. To improve it, this paper proposes a new image segmentation algorithm based on quantum annealing and Graph Cuts. The algorithm beds the classical interactive image segmentation problem into a quantum optimization algorithm and obtains ideal image segmentation results on the D-Wave quantum annealer. Meanwhile, it is compared with the other three methods. Compared with MATLAB, the segmentation results are more beautiful, with an average precision higher than 5.27% and an average recall higher than 5.43%; the quantum annealing time is always lower than the simulated annealing time; and the success probability is more than twice that of the quantum approximate optimization algorithm. Therefore, it is concluded that this method is superior. [ABSTRACT FROM AUTHOR]

The discrete-logarithm problem and related problems are important in public-key cryptography; however, these problems can be reduced to the hidden-subgroup problem (HSP) of an abelian group, for which efficient quantum algorithms exist. This paper more broadly regards these problems as semigroup-action problems (SAPs) on different modules. The results prove that if the action on a module is injective or the cardinality of the hidden subgroup's least generating set is less than or equal to that of the ring's least generating set, the corresponding SAP on the module can be reduced to the HSP of an abelian group in polynomial time; therefore, most cryptosystems based on the SAP on a module cannot resist quantum cryptanalysis. The results are applicable to the discrete-logarithm problem and matrix-action problem on a group, along with other SAPs on a module. Such reduction is not be found for the SAP on the semi-module. The cryptographic systems based on SAPs on some semi-modules are likely to resist quantum attacks. [ABSTRACT FROM AUTHOR]

The assumption of measurement independence is essential for the derivation of Bell's inequalities under local, realistic conditions. Violations of these inequalities indicate that the assumption of measurement independence must be relaxed to some extent in order to obtain locally realistic models. The extent to which this assumption needs to be relaxed to achieve violations of certain bipartite Bell inequalities has been studied in Hall (Phys Rev Lett 105:250404, 2010) and Friedman (Phys Rev A 99:012121, 2019). In this paper, we investigate the minimal degree of relaxation required to simulate violations of various known tripartite Bell inequalities. We also provide local deterministic models that achieve these violations. [ABSTRACT FROM AUTHOR]

This paper proposes a scalable three-level hierarchical quantum information splitting (HQIS) protocol with double quantum unknown states. Generally, the traditional HQIS is to distribute the secret to two levels of receivers for purpose of achieving the secret recovery with the help of some receivers to recover the secret. Our proposed protocol uses the product states of two four-particle cluster states and two three-particle GHZ state as quantum channels to transmit the information of double-quantum unknown states, which can face more complex application scenarios and realize the extension of the agent level. By using multi-qubit GHZ state, the proposed protocol can be modified and extended to achieve the change of the number of agents, and it can make the scheme scalable. Finally, we analyzed the efficiency and safety of the scheme and gave a comparison of its similar schemes. [ABSTRACT FROM AUTHOR]

This paper presents a quantum image encryption algorithm based on a novel 3D chaotic system and the quantum Rubik's cube principle. Initially, we propose a new 3D chaotic system for generating chaotic key sequences and chaotic images. Subsequently, we introduce the quantum Rubik's cube principle, which serves as a fundamental component of our encryption scheme. The scheme consists of two stages: In the first stage, chaotic key sequences control the operation of the quantum Rubik's cube principle, enabling pixel permutation in the encrypted image. In the second stage, the scrambled image undergoes bitwise XOR with the chaotic image, facilitating pixel diffusion through quantum bitwise XOR operations. By leveraging the chaotic system's sensitivity to initial values and its large key space, our proposed scheme effectively resists statistical attacks and noise interference. The time complexity of our scheme is exponential reduced compared to its classical counterpart. We also conduct experiments on both the IBM Qiskit platform and a classical computer and analyze the results. [ABSTRACT FROM AUTHOR]

With the rapid development of quantum computing technology, the traditional cryptosystem will face a significant threat. It is an urgent security issue to study the security impact of quantum computing on classical cryptosystems and provide reliable cryptographic primitives for the post-quantum era. A powerful way to solve this problem is to quantize the classical cryptanalysis tools and use the improved versions for cryptanalysis. In this paper, we propose a quantum Zero-correlation analysis algorithm based on the Bernstein–Vazirani and Grover algorithms. It can find zero-correlation linear hulls for Feistel and SPN structures. We prove the correctness of the algorithm and analyze its complexity. Compared with the classical algorithms, the proposed quantum algorithm has significant advantages when the number of encryption rounds of block ciphers is large. Moreover, compared with the existing quantum Zero-correlation linear analysis, the proposed algorithm is more efficient and does not depend on the algebraic characteristics of the target cipher, which makes the algorithm has more flexible application scenarios. With the development of quantum computers, we discuss the threat of quantum cryptanalysis algorithms to classical security. [ABSTRACT FROM AUTHOR]

There are various challenges facing quantum watermarking, of which the most significant one is that unlike classical watermarking, there remain few achievements made to build a complete system. Allowing for this, a two-domain quantum color image watermarking scheme based on least significant bit (LSB) algorithm is proposed in this paper. For the purpose of image representation, the image of the carrier and that of the watermark are represented through the novel quantum representation of color digital images (NCQI) (Sang et al. in Quantum Inf Process 16:1–14, 2017), the size of which is 2 n × 2 n and 2 n - 1 × 2 n - 1 , respectively. Firstly, the watermark image is scrambled by conducting operation on the color and position of the image. Through this simultaneous scrambling of color and position, the privacy of watermark images is better protected. Secondly, the scrambled watermark image is embedded into the spatial domain of the carrier image using the LSB algorithm. Additionally, the scrambled watermark image is embedded into the frequency domain of the carrier image through quantum Fourier transform and LSB algorithm, thus improving the capability to withstand illegal attacks. Lastly, both simulation experiment and comparative analysis are conducted to demonstrate the satisfactory visual quality of the proposed scheme and its strong robustness to the salt and pepper noises. These positive findings contributed to enriching the existing theory of color quantum image watermarking. [ABSTRACT FROM AUTHOR]

Quantum computation is growing in significance and proving to be a powerful tool in meeting the high real-time computational demands of classical digital image processing. However, extensive research has been done on quantum image processing, mainly rooted in binary quantum systems. In this paper, we propose a new quantum ternary image circuit based on the analysis of the existing qutrit representation of quantum images. The proposed design utilizes ternary shift gates and ternary Muthukrishnan–Stroud gates, with the belief that this circuit can be used for ternary quantum image processing. This study makes a significant improvement compared to the existing counterpart in terms of quantum cost, the number of constant inputs, and garbage outputs, which are all essential parameters in quantum circuit design. [ABSTRACT FROM AUTHOR]

The current blockchain systems lack the ability to resist quantum computing attacks. This puts the confidentiality and integrity of data in blockchain-based data sharing at risk. The security of data sharing faces the new challenges. In this paper, a blockchain data sharing scheme based on quantum re-encryption is proposed. The presented scheme uses quantum key and unitary matrix to encrypt data for two times. It ensures data sharing between the data owner and the data accessor without revealing the owner's private key. Moreover, it utilizes a quantum hash function based on controlled alternate quantum walks to compute quantum hash value. The obtained hash value has higher randomness, collision resistance and input sensitivity. Additionally, this method combines on-chain and off-chain storage. The combined storage method effectively alleviates the storage pressure on the blockchain. Finally, the security of the proposed scheme is analyzed. The results show that this scheme ensures the integrity, confidentiality and non-tampering of the shared data. At the same time, it protects the security of data owner's private keys. [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]