Trojan Threats in Quantum Computing Hardware: SFQ Control and Readout Vulnerabilities

The frequency-sensitive properties of superconducting systems render them susceptible to malicious attacks, which pose significant risks to quantum computing hardware. A novel single flux quantum (SFQ)-based hardware Trojan, termed as pulse-interleaved Trojan (PI-Trojan), designed to exploit these vulnerabilities is investigated in this paper. Embedded within a frequency divider circuit, the PI-Trojan is evaluated for its threat potential at different frequencies. The Trojan is designed to remain inactive during standard low-frequency testing and to be selectively activated at higher operational frequencies, specifically targeting qubit control and readout operations. Extensive simulations demonstrate the PI-Trojan ability to disrupt clock signals, which can potentially destabilize qubit synchronization, and compromise data integrity, emphasizing the urgent need for a robust security framework to protect superconducting quantum systems from such covert threats.