  Quantum computing introduces unfamiliar security vulnerabilities demanding
customized threat models. Hardware and software Trojans pose serious concerns
needing rethinking from classical paradigms. This paper develops the first
structured taxonomy of Trojans tailored to quantum information systems. We
enumerate potential attack vectors across the quantum stack from hardware to
software layers. A categorization of quantum Trojan types and payloads is
outlined ranging from reliability degradation, functionality corruption,
backdoors, and denial-of-service. Adversarial motivations behind quantum
Trojans are analyzed. By consolidating diverse threats into a unified
perspective, this quantum Trojan taxonomy provides insights guiding threat
modeling, risk analysis, detection mechanisms, and security best practices
customized for this novel computing paradigm.
