Quantum Communication, Networks, and Secure Information Processing in a Three-Axiom Global-Realist Framework

Abstract

We develop a unified, operational, and falsifiable framework for quantum communication, quantum networks, and quantum cryptography as a conservative extension of three physical axioms: microscopic ontic definiteness with finite localization, the physical reality of the spacetime–vacuum substrate, and persistent causal retarded source–response coupling. Quantum states, density operators, entanglement, channels, and information are treated as mathematical or operational representations rather than additional fundamental ontologies. The framework derives completely positive trace-preserving maps from unitary system–environment dynamics and examines Kraus, Choi, Liouville, Stinespring, complementary-channel, and process-tensor representations. It establishes explicit interfaces for initial system–environment correlations, non-Markovian memory, channel discrimination, diamond-norm certification, and causal multitime processes. Classical, quantum, private, and entanglement-assisted capacities are distinguished from finite-blocklength and resource-normalized throughput. Optical-fiber, free-space, atmospheric, satellite, deep-space, microwave, atomic, spin, and continuous-variable links are incorporated through complete source–channel–receiver–detector forward models. Quantum networks are formulated as stochastic renewal, memory, swapping, purification, routing, and queueing systems subject to cut-set bounds, decoherence, synchronization error, congestion, latency, and energy constraints. For quantum key distribution, the security chain proceeds from source characterization and parameter estimation through smooth min-entropy, entropic uncertainty, error correction, authentication, privacy amplification, and composable key certification. BB84, decoy-state, entanglement-based, measurement-device-independent, device-independent, and continuous-variable protocols are treated with explicit finite-size and assumption boundaries. The theory preserves operational no-signaling, finite propagation speed, passivity, and complete energy accounting. Every performance or security claim requires independent calibration, nuisance covariance, held-out prediction, finite-sample validation, matched classical comparison, and an explicit rejection criterion. **Keywords** Quantum communication; quantum channels; quantum networks; quantum cryptography; quantum key distribution; open quantum systems; channel capacity; continuous-variable communication; quantum repeaters; process tensors; non-Markovian dynamics; composable security; finite-key analysis; no-signaling; detector forward models; experimental identifiability.