ABSTRACT We investigate how a homogeneous, isotropic dielectric modifies the resonance interaction energy of two atoms in a maximally entangled state undergoing synchronized motion. Our analytical and numerical results reveal that the magnitude, sign, and spatial profile of the interaction are governed by a subtle interplay among four key control knobs: the atoms' common velocity, the medium's refractive index, the interatomic separation, and the orientation of their electric dipole moments. By precisely tuning these parameters, one may not only amplify or suppress the interaction strength but also trigger a complete inversion of its character, converting attraction into repulsion or vice versa. The most dramatic departure from conventional behavior can occur at the Cherenkov threshold, . In the short‐distance regime, the resonance energy scales as , abandoning the familiar scaling characteristic of subluminal or superluminal motion and of free‐space configurations. The slower power‐law decay endows the interaction with an extended effective range, while its amplitude is universally diminished relative to the off‐threshold cases. Our findings establish that the synergistic interplay between a dielectric medium and uniform relativistic motion provides a tunable mechanism to control resonance interactions in entangled atomic pairs.

ABSTRACT Quantum key distribution (QKD) enables long‐distance secret keys transmission with information‐theoretic security. However, weak‐randomness obviously limits the security of practical QKD systems. This may leak the key information by considering the imperfect devices. In this work, we proposed a practical security analysis model that simultaneously considers the bit‐weak‐randomness and the basis‐weak‐randomness parameters, which we refer to as the weak‐randomness model. First, we establish a novel bit‐weak‐randomness model based on the virtual mutually unbiased bases method. Subsequently, under the framework of information‐theoretic security proof, we proposed a comprehensive weak‐randomness model by incorporating the basis‐weak‐randomness model. Then, we characterize the relationship between typical quantum attacking strategies and weak‐randomness parameters. Based on our proposed weak‐randomness model, we perform a security analysis against these attacks. Finally, we perform numerical simulations of the weak‐randomness model based on the advantage distillation method, considering both single photon sources and weak coherent sources. Our results can provide a model capable of characterizing security parameters to simultaneously account for the impacts of both imperfect devices and quantum hacking. This enables a unified standard for evaluating the security levels of practical QKD systems and offers a theoretical foundation for QKD system testing and assessment.

ABSTRACT Diffusion models excel in generative modeling for complex distributions, but suffer from parameter inefficiency. Quantum variants partly address this via quantum resources, yet significant room remains for enhancing denoising efficiency. A quantum denoising diffusion model based on Gaussian boson sampling is proposed to further enhance denoising efficiency, which employs a trainable boson sampling circuit instead of traditional neural networks for backward denoising. Our model demonstrates superior denoising efficiency compared to both selected quantum denoising diffusion models and classical diffusion models(specified later in the text) on the MNIST handwritten digit dataset under the same number of training parameters. Moreover, our model achieves good denoising results under four different noise addition methods, which indicates its robust generalization capabilities. These results provide a paradigm for enhancing the denoising efficiency of quantum denoising diffusion models.

ABSTRACT Manipulating 2D spintronics and valleytronics by external means is a great challenge in information technology. Building van der Waals (vdW) heterostructure (HS) has been proved to be an efficient method for realizing the control of spin and valley degrees of 2D materials. Here, we discovered that the TeB/CrI 3 HSs with both α‐ and β‐phase TeB monolayers display ferromagnetic (FM) semiconductor and FM metal characters with type‐II band alignments and elevated Curie temperature. By applying biaxial strains, semiconductor‐to‐metal transition and type‐II to type‐III conversion occur for α‐TeB/CrI 3 HS and β‐TeB/CrI 3 HS, respectively. Notably, the valley polarization in β‐CrI 3 /TeB HS can be further tuned under strains, resulting from the broken symmetry and magnetic proximity effect. Our findings provide a microscopic insight into 2D controllable spintronic and valleytronic devices.

ABSTRACT Single‐photon sources are essential for testing fundamental physics and for the development of quantum technologies. In this work, a single‐photon source is investigated, based on a two‐photon Jaynes–Cummings system, where the resonator works as the quantum emitter rather than the two‐level system. This role reversal provides certain advantages, such as robustness against losses from the two‐level system (e.g., dephasing), as it remains in its ground state throughout the entire dynamics. This provides higher efficiency, purity, and indistinguishability compared to sources based on the usual Jaynes–Cummings model under the same parameter conditions in both models. Another advantage of this system is the possibility of direct conversion of a coherent excitation pulse with one photon on average to a single‐photon pulse with efficiency, purity, and indistinguishability above . Since the entire excitation pulse is consumed in the generation of a single photon, the system also minimizes energy waste. The potential for implementing the two‐photon JC model across different platforms expands the possibilities for controlled single‐photon generation in applications in quantum information processing and computation.

ABSTRACT Quantum secret sharing aims to securely distribute private information among multiple participants, such that only authorized subsets can collaboratively reconstruct the secret. However, current research remains largely exploratory, and most existing protocols are limited to sharing low‐dimensional quantum states and lack hierarchical capabilities. To overcome these limitations, we propose a novel hierarchical quantum secret sharing protocol with identity authentication. Specifically, we construct ‐dimensional disentangler and isometric transformation operations. These are applied to compress arbitrary ‐dimensional entangled states, with each compression corresponding to one hierarchical level. For a given hierarchical participant structure, the entangled particles of the compressed states are allocated as secret shares among the participants. Authorized participants within the same level collaboratively reconstruct the original quantum state using the conjugate transposes of disentangler operations and isometric transformations. Security analysis confirms the protocols resilience against common attacks, including intercept‐resend, entangle‐measure, and dishonest participant attacks. Compared with existing similar protocols, our scheme demonstrates superior performance in terms of quantum efficiency and other metrics.

ABSTRACT Scaling beyond individual quantum devices via distributed quantum computing relies critically on high‐fidelity quantum state transfers between devices, yet the quantum interconnects needed for this are currently unavailable or expected to be significantly noisy. These limitations can be bypassed by simulating ideal state transfer using quasiprobability decompositions (QPDs). Wire cutting, for instance, allows this even without quantum interconnects. Nevertheless, QPD methods face drawbacks, requiring sampling from multiple circuit variants and incurring substantial sampling overhead. While prior theoretical work showed that incorporating noisy interconnects within QPD protocols could reduce sampling overhead relative to interconnect quality, a practical implementation for realistic conditions is lacking. Addressing this gap, this work presents a generalized and practical QPD for state transfer simulation using noisy interconnects to reduce sampling overhead. The QPD incorporates a single tunable parameter for straightforward calibration to any utilized interconnect. To lower practical costs, the work also explores reducing the number of distinct circuit variants required by the QPD. Experimental validation on contemporary quantum devices confirms the proposed QPD's practical feasibility and expected sampling overhead reduction under realistic noise. Notably, the results show higher effective state transfer fidelity than direct transfer over the underlying noisy interconnect.

ABSTRACT Quantum tests directly reveal the incompatibility of quantum and classical predictions. The violation of such a test establishes a quantifiable gap between the capabilities of observers with access to classical resources and those utilizing quantum entanglement. Typically, larger violations indicate a higher degree of quantumness—for instance, enabling quantum self‐testing in Bell scenarios, where achieving maximal violation is highly desirable. The self‐guided method, initially developed for finding maximal Bell violations, is later extended to complex variables. Here, we apply and compare both variants to determine the maximal violation of the instrumental inequality. The complex‐number variant generally exhibits faster convergence, except during the initial phase. This improvement is more evident in instrumental tests, likely due to their simpler causal structure compared to Bell scenarios. Our findings establish the self‐guided method with complex variables as a generally applicable and competitive approach for robustly and efficiently identifying maximal violations across diverse quantum tests.

ABSTRACT We propose a system for channeling plasmon‐enhanced polarized single photons into optical nanowire‐guided modes. We show that the spontaneous emission properties of quantum emitters can be strongly enhanced in the presence of a gold nanorod dimer, leading to the emission of highly polarized and bright single photons. We numerically calculate the Purcell factor as high as ∼ 19150 and a radiative quantum efficiency of ∼ 0.8. This yields a coupling efficiency of ∼ 13% into the guided modes of the optical nanowire with an enhancement factor of ∼ 1990 and a high degree of polarization of > 99% for fiber‐coupled single photons. We show that the gold nanorod dimer system can yield an order of magnitude enhancement of the spontaneous emission characteristics as compared to a single gold nanorod. This proposed hybrid quantum system can be in line with fiber networks and may open new avenues for quantum information applications.

ABSTRACT The spin‐boson model's dynamical and thermodynamic features in the weak coupling regime are investigated using the weak coupling spin‐boson (WCSB) and phase covariant (PC) master equations. Both unital (pure dephasing) and non‐unital (dissipative) quantum channels are considered. On the dynamical side, key quantum features including non‐Markovianity, quantum speed limit, quantum coherence, and the system's steady‐state behavior, are explored. Notably, the measures of non‐Markovianity exhibit different behavior under WCSB and PC dynamics. From the quantum thermodynamic perspective, the spin‐boson system is conceptualized as a quantum battery and analyze its performance through metrics such as energy, ergotropy, anti‐ergotropy, and battery capacity. The roles of pure dephasing and dissipative processes in shaping the battery's performance are further examined. The findings demonstrate the spin‐boson model's versatility as a platform for efficient energy storage and transfer in quantum thermodynamic devices.