Abstract The monogamy and polygamy properties of quantum entanglement characterize fundamental constraints on the distribution of entanglement in multipartite quantum systems. In this paper, we investigate tighter monogamy and polygamy relations for multipartite entanglement. By establishing a new mathematical inequality, we derive a family of improved monogamy and polygamy inequalities for tripartite quantum systems and further extend these results to general multipartite systems. Comparisons with existing results show that the obtained bounds are tighter. Illustrative examples are provided to demonstrate the effectiveness of the proposed relations.

Abstract Named data networking (NDN) supports receiver-driven content retrieval with stateful forwarding (pending interest table (PIT)/forwarding information base) and in-network caching, yet many deployments still rely on classical cryptography that may be undermined by quantum-capable adversaries. Despite NDN’s built-in data authenticity via producer signatures, quantum-enabled attacks become plausible once RSA/ECC-based trust anchors are weakened by Shor-type attacks. Existing quantum-security efforts for NDN largely focus on post-quantum replacements of signatures or key exchange, but do not address the tension between confidentiality-preserving payload protection and NDN’s in-network processing (forwarding/caching decisions) in a quantum setting. This paper presents a quantum-enhanced NDN architecture that preserves NDN’s content-centric semantics—naming, PIT-driven forwarding, and cache-assisted dissemination of verifiable control objects—while delivering privacy-sensitive payloads as quantum homomorphic encryption (QHE)-encrypted quantum states over an underlying quantum network. QHE provides end-to-end confidentiality and enables authorized operations on encrypted quantum payloads without exposing plaintext. To make the design compatible with NDN forwarding, the proposed protocol encrypts the payload while keeping name-based forwarding semantics intact, and supports ciphertext-domain processing for selected policy functions. To protect provenance and integrity of NDN metadata, routing instructions, and session state, we incorporate quantum digital signatures (QDS) bound to NDN names and session identifiers. The main contributions are: (i) a QHE+QDS layered protection model tailored to NDN’s Interest and Data exchange; (ii) a session workflow that couples proactive entanglement distribution with NDN-style stateful signaling for efficient establishment and recovery; and (iii) a security analysis clarifying the achieved guarantees and the remaining trust assumptions. Security analysis indicates robustness against quantum man-in-the-middle and tampering attacks, with modest overhead on NDN control traffic.

Abstract In practice today, quantum keys are often reused because of practical limitations. It is clear that reusing a key weakens security compared to one-time-pad encryption, where perfect secrecy is achieved. For this reason, it is important to understand how the effort needed to find the key changes when the key is reused. We use the trace distance between two quantum states as a measure of closeness. Its maximum value is one, which means the two states are as different as possible. With simple arguments, we show that the trace distance is bounded above by several terms that capture (i) non-ideal quantum keys, (ii) plaintext redundancy, (iii) the number of key reuses, and (iv) the number of collisions of the block cipher. The trace distance approaches one exponentially fast with plaintext redundancy and with the number of key reuses; this means brute-force search becomes as easy as possible. For a random block cipher, the expected trace distance grows linearly with the number of key uses, with coefficient e −1 ( e is Euler’s constant). The result is information-theoretic in nature.

Abstract We introduce a paradigm of spectral engineering for environmental noise aimed at actively protecting quantum coherence in solid-state qubits. Through the analytical study of the decoherence process induced by cavity leakage in a double-quantum-dot–cavity system, we demonstrate high-frequency charge noise can effectively freeze the quantum state and protect quantum coherence. Then, departing from conventional noise-suppression strategies, we propose to synthesize tailored noise spectra by linearly mixing multiple Ornstein–Uhlenbeck (OU) stochastic processes. The composite noise is designed to possess a power spectral density enriched in high-frequency components which is required for coherence protection. Our method provides a general framework for approximating arbitrary noise profiles, including the ubiquitous <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>1</mml:mn> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:mi>f</mml:mi> </mml:mrow> </mml:math> spectrum prevalent in semiconductor devices, using only a finite set of simple noises. Numerical simulations confirm that a noise field synthesized from a sufficiently large number of OU processes preserves coherence significantly better than one constructed from just a few components. This work establishes noise engineering as a practical tool for coherence management and offers a versatile model for simulating complex noise environments in quantum information platforms.

Abstract Topological quantum plasmas provide a groundbreaking platform for high-efficiency terahertz generation through nonlinear wave mixing. A comprehensive theoretical framework is presented by combining quantum hydrodynamics with Maxwell’s equations to demonstrate that Dirac fermions in materials like graphene and topological insulators exhibit a giant third-order nonlinear susceptibility enhanced by linear band dispersion, Berry phase effects, and spin-momentum locking. The predicted terahertz emission efficiency exceeds conventional semiconductor plasmas by 2–3 orders of magnitude, reaching enhancement factors of 25–1250 times across different Dirac materials. The analysis reveals that the combination of quantum plasmon dispersion and intrinsic Dirac fermion nonlinearity enables exceptional spectral tunability through pump frequency and chemical potential control. This work establishes topological quantum plasmas as a superior platform for compact, efficient on-chip terahertz sources, providing a transformative pathway to bridge the longstanding ‘THz gap’ in photonic technology.

Abstract This paper systematically investigates the coherence dynamics of a two-qubit system under correlated channels. Through density matrix transformation and operator algebra derivation, we analyze the regulatory effects of memory properties of correlated amplitude damping, phase damping, and depolarization channels on three kinds of coherence, namely l 2 -norm coherence, Tsallis 2-relative entropy coherence, and Rényi 2-relative entropy coherence. The results show that phase damping and depolarization channels induce coherence freezing under perfect memory conditions, where coherence values remain invariant with channel damping rate variations. In partial memory environments, l 2 -norm coherence exhibits superior stability and retains coherence more efficiently than the other two coherence measures. In addition, we quantitatively evaluate the cohering and decohering power of these coherences under the correlated amplitude damping channel. This work provides theoretical support for anti-noise design of quantum technologies in open quantum systems.