This paper investigates the application of Security Threat Discovery Cards (STDCs) for identifying security risks in quantum sensing technologies within port security contexts. With the advent of quantum technologies, organizations and stakeholders face the challenge to explore and assess the impact of the applications these technologies will bring. This exploration faces the perceived incomprehensibility of quantum technologies, and suggests a preliminary step aimed at understanding these technologies. Our results suggest that organizations and companies considering the application of quantum technology can skip this preliminary step and independently identify their main risks of quantum applications in a nuanced manner. Our case is an exploration of quantum sensing application by Port security personnel with the STDCs. The research consisted of two independent empirical studies: a workshop with Port of Moerdijk personnel using STDCs and semi-structured interviews with security experts. The comparative analysis of the findings from these studies demonstrates the STDCs’ efficacy in revealing with the Port’s personnel assessment of nuanced risks beyond the experts’ foresight. For example, the interviews with experts raised concerns regarding governance, ethical implications, and the human factor in quantum technology integration. The workshop with personnel not only suggested similar concerns but also uncovered additional risks, including socio-technical threats and broader societal impacts.