ABSTRACTThis study presents the challenges of learning deformable offsets in conventional machine learning (ML) systems. It significantly focuses on the representation data derived from the MNIST and FashionMNIST datasets. The primary difficulty with this approach is optimising a trade‐off between accuracy and efficiency by exploiting the gradient‐based algorithm. It is a significant phase of the image recognition and transformation process. Provide a strategy for incorporating quantum approaches utilising quantum loss functions, entanglement, and quantum feature maps to improve on conventional gradient‐based techniques. Employ hybrid ways that combine quantum algorithms, such as quantum natural gradient descent (QNGD) and variational quantum eigensolver (VQE), with classical optimisation techniques. This approach is applied to updating deformable offsets and optimising quantum eigenvalue issues. We use quantum Fisher information matrices (FIM) and train tensor networks efficiently and accurately. Then, we performed extensive tests comparing the quantum method with established conventional baselines through hyperparameters, such as accuracy, precision, recall and F1 score. The implementation results demonstrate significant gains in classification accuracy, which exhibit 97% on the MNIST dataset and 87% on the FashionMNIST dataset. The result of the paper emphasises significant conclusions, including improved model stability, increased generalisability and decreased overfitting, due to implementing quantum optimisation techniques. With quantum principles applied to convolution and feature extraction, such data exhibit substantial potential in processing.

ABSTRACT Medical image integrity is critical as telemedicine, cloud PACS and AI‐assisted diagnostics become routine. We present a tamper localisation framework that embeds authentication signatures in the phase domain of blockwise quantum Fourier transform (QFT) coefficients. The watermark is phase‐only, energy preserving and keyed through sparse midband supports with paired phase differences; a light cross‐block coupling imposes spatial consistency so that localised edits produce coherent high‐contrast residuals confined to manipulated regions after inverse QFT. Because magnitudes remain unaltered, benign photometric variations are naturally attenuated, improving specificity under common acquisition and storage pipelines. The verifier computes circular phase residuals and applies an adaptive threshold to generate blockwise tamper maps, which are refined to pixel resolution. Across standard distortions (JPEG recompression, Gaussian noise and blur) and localised forgeries (copy–move, inpainting and contrast edits), the scheme maintains diagnostic fidelity (typical PSNR 40 dB, SSIM 0.98) while delivering precise spatially resolved detection. The design is deterministic and reproducible via seeded keys, integrates with DICOM workflows and is amenable to future quantum hardware realisation. This work contributes a quantum‐ready, imperceptible and localisation‐oriented approach to medical image authentication suitable for deployment in modern healthcare systems. The proposed QFT phase–only watermark achieves imperceptibility (global PSNR dB; SSIM ) and detects localised tampering (ROC AUC under class imbalance).

ABSTRACT The emergence of quantum computing has introduced unprecedented security challenges to conventional cryptographic systems, particularly in the domain of classical communications. Our research addresses these challenges by creatively combining quantum key distribution (QKD), specifically the E91 protocol, with logistic chaotic maps to establish a secure image transmission scheme. Our approach utilises the pseudo‐randomness of chaotic systems alongside the security mechanisms inherent in quantum entanglement‐based protocols. This framework leverages the E91 protocol for secure quantum key distribution to generate identical key pairs at both ends, followed by chaos encryption using the key as a basis for the parameters. This framework utilises the E91 protocol for secure quantum key distribution, leveraging maximally entangled pairs and CHSH inequality tests to detect eavesdropping and potential double‐agent attacks by identifying nonentangled qubits, therefore maintaining key confidentiality. Furthermore, through quantitative simulations, we demonstrate the effectiveness of this scheme through key space and key sensitivity analysis, histogram analysis, information entropy analysis, execution time analysis, and differential attack analysis in end‐to‐end encryption. The results indicate a significant improvement in encryption and decryption efficiency, showcasing the scheme's potential as a viable solution against the vulnerabilities posed by quantum computing advancements. Our research offers a novel perspective on a critical aspect of cybersecurity applications across healthcare, defence, finance, and beyond in the realm of secure quantum communication.

Abstract High‐dimensional quantum states, or ‘qudits’, provide significant advantages over traditional qubits in quantum communication, such as increased information capacity, enhanced noise resilience, and reduced information loss. Despite these benefits, their implementation has been constrained by challenges in generation, transmission, and detection. This paper presents a novel theoretical framework for transmitting quantum information using qudit entanglement distribution over a superposition of causal orders in two quantum channels. Using this model, a quantum switch operation for 2‐qudit systems is introduced, which facilitates enhanced fidelity of entanglement distribution and quantum teleportation. The results demonstrate that the use of qudits in entanglement distribution achieves a fidelity improvement from 0.5 (for qubit‐based systems) to 0.94 for 20‐dimensional qudits, even under noisy channel conditions. This enhancement is achieved by exploiting the increased Hilbert space of high‐dimensional states and the inherent noise‐resilience properties of quantum switches operating in superpositions of causal orders. The findings underscore the potential of qudit‐based quantum systems in achieving robust and high‐fidelity communication in environments where traditional qubit‐based systems face limitations.

ABSTRACTQuantum key distribution (QKD) has often been hailed as a reliable technology for secure communication in cyber–physical microgrids. Even though unauthorised key measurements are not possible in QKD, attempts to read them can disturb quantum states leading to mutations in the transmitted value. Further, inaccurate quantum keys can lead to erroneous decryption producing garbage values, destabilising microgrid operation. QKD can also be vulnerable to node‐level manipulations incorporating attack values into measurements before they are encrypted at the communication layer. To address these issues, this paper proposes a secure QKD protocol that can identify errors in keys and/or nodal measurements by observing violations in control dynamics. Additionally, the protocol uses a dynamic adjacency matrix‐based formulation strategy enabling the affected nodes to reconstruct a trustworthy signal and replace it with the attacked signal in a multi‐hop manner. This enables microgrids to perform nominal operations in the presence of adversaries who try to eavesdrop on the system causing an increase in the quantum bit error rate (QBER). We provide several case studies to showcase the robustness of the proposed strategy against eavesdroppers and node manipulations. The results demonstrate that it can resist unwanted observation and attack vectors that manipulate signals before encryption.

ABSTRACTWith the rising demand for secure and reliable telecommunication networks, efficient resource allocation strategies in quantum key distribution‐based software‐defined optical networks (SDONs) are becoming essential. In this research, we propose a heuristic adaptive quantum routing (RWTA_AQR) algorithm for routing, wavelength and timeslot assignment. RWTA_AQR utilises the FirstFit algorithm to assign wavelengths in both contiguous and noncontiguous timeslots for optimal resource utilisation based on the priority. To verify its effectiveness, the proposed RWTA_AQR is tested on NSFNET and UBN24 network topologies under diversified traffic models, towards low as well as high demand, network congestion scenarios. We use network security performance (NSP), success ratio of connection requests, timeslot utilisation, quantum key utilisation, blocking probability (BP) and security downgrade ratio as metrics to prove its effectiveness against the existing methods based on flexible security level, strict security level and classical approach. The results demonstrate that RWTA_AQR performs better by allowing NSP of up to 90% and having the lowest BP (below 10%) at lower traffic load. The proposed solution provides a systematic trade‐off in security and resource utilisation with controlled overhead for improving the performance of QKD‐SDONs in dynamic resource‐constrained environments.

Abstract Hyperentangled swapping is a quantum communication technique that involves the exchange of hyperentangled states, which are quantum states entangled in multiple degrees of freedom, to enable secure and efficient quantum information transfer. In this paper, we demonstrate schematics for the hyperentanglement swapping between separate pairs of neutral atoms through the mathematical framework of atomic Bragg diffraction, which is efficient and resistant to decoherence, yielding deterministic results with superior overall fidelity. The utilised cavities are in a superposition state and interact with the incoming atoms off‐resonantly. Quantum information carried by the cavities is swapped through resonant interactions with two‐level auxiliary atoms. We also discuss entanglement swapping under a delayed‐choice scenario and provide a schematic generalisation covering multiple‐qubit scenarios. Finally, we introduce specific experimental parameters to demonstrate the experimental feasibility of the scheme.

Abstract Given the diverse array of physical systems available for quantum computing and the absence of a well‐defined quantum Internet protocol stack, the design and optimisation of quantum networking protocols remain largely unexplored. To address this, the authors introduce an approach that facilitates the establishment of paths capable of delivering end‐to‐end fidelity above a specified threshold, without requiring detailed knowledge of the quantum network's properties. In this study, the authors define algorithms that are specific instances of this approach and evaluate them in comparison to Dijkstra's shortest path algorithm and a fully knowledge‐aware algorithm through simulations. The authors’ results demonstrate that one of the proposed algorithms consistently outperforms the other methods in delivering paths above the fidelity threshold, across various network topologies and the number of source‐destination pairs involved, while maintaining significant levels of fairness among the users and being robust to inaccurate estimations of the expected end‐to‐end fidelity.

ABSTRACT Quantum key distribution (QKD) allows two users to exchange a provably secure key for cryptographic applications. In prepare‐and‐measure QKD protocols, the states must be indistinguishable to prevent information leakage to an eavesdropper performing a side‐channel attack. Here, we measure the indistinguishability of quantum states in a prepare‐and‐measure three‐state BB84 polarisation‐based decoy state protocol using resonant‐cavity light‐emitting diodes (RC‐LEDs) as the source in the transmitter. We make the spatial, spectral and temporal DOF of the generated quantum states nearly indistinguishable using a spatial filter single‐mode fibre, a narrow‐band spectral filter and adjustable timing of the electrical pulses driving the RC‐LEDs, respectively. The sources have fully indistinguishable transverse spatial modes. The measured fractional mutual information between an assumed eavesdropper and the legitimate receiver is due to the spectral distinguishability and for the temporal distinguishability. The source is integrated into a full QKD system operating in a laboratory environment, where we achieve a secure key rate of 41.5 kbits/s with an average quantum bit error rate of 2.9%. The low system size, weight and power make it suitable for mobile platforms such as uncrewed aerial vehicles (drones) or automobiles.

ABSTRACT Many quantum algorithms operate on classical data, by first encoding classical data into the quantum domain using quantum data encoding circuits. To be effective for large data sets, encoding circuits that operate on large data sets are required. However, as the size of the data sets increases, the encoding circuits quickly become large, complex and error prone. Errors in the encoding circuit will provide incorrect inputs to quantum algorithms, making them ineffective. To address this problem, a formal method is proposed for verification of encoding circuits. The key idea to address scalability is the use of abstractions that reduce the verification problem to bit‐vector space. The major outcome of this work is that using this approach, the authors have been able to verify encoding circuits with up to 8191 qubits with very low memory (85 MB) and time (0.29s), demonstrating that the proposed approach can easily be employed to verify even much larger encoding circuits. The results are very significant because, traditional verification approaches that rely on modelling quantum circuits in Hilbert space have only demonstrated verification scalability up to 250 qubits. Also, this is the first approach to tackle the verification of quantum encoding circuits.