Outline Toshiba Europe Limited has been at the forefront of quantum communication for over a decade, pioneering technologies that set new standards in cryptography and data security. Our research underpins deployed Quantum Key Distribution (QKD) systems and continues to drive innovation in next generation quantum secure networking. This includes the development of new advanced protocols such as Twin Field QKD and entanglement based approaches, pushing the boundaries of what is possible in quantum secure communications. We invite applications for the post of Research Scientist in the Quantum Information Group of the Cambridge Research Laboratory of Toshiba. The successful applicant will take responsibility for developing implementation aware security proofs for quantum cryptography systems, helping ensure that theoretical guarantees remain robust when real device behaviour and system level constraints are accounted for. This is an opportunity to join a dynamic and world leading team, supported by one of the best-known companies in digital electronics and services, in which you will collaborate closely with experimentalists, and system designers, contributing theoretical insight to modelling, system architecture, and protocol development. Key Responsibilities Security & Protocol Theory Develop and refine finitesize discretevariable QKD security proofs. Incorporate experimentally characterised device behaviour into theoretical models. Analyse existing QKD protocols and propose improvements to performance and security. Modelling & Simulation Use and extend QKD simulators to evaluate protocol performance under realistic conditions. Integrate experimental datasets to validate assumptions and improve modelling accuracy. Provide modellingdriven input to system engineering decisions. Collaboration & Contribution Work closely with experimental and systems teams to ensure theoretical models and security assumptions reflect practical implementation details. Contribute to joint research activities with academic and industrial partners. Write internal reports, coauthor scientific publications, and present work at conferences when appropriate. Contribute to efforts to develop global standards for quantum technologies. Skills & Experience (Essential) PhD in Physics, Electronic Engineering, Mathematics, or a related field. Familiarity with finitesize discretevariable QKD securityproof techniques. Experience using QKD simulators to model protocol and system behaviour. Understanding of experimental QKD concepts and optical/photonic device behaviour. Evidence of research excellence through publications or equivalent results. Ability to work effectively in a collaborative research environment. Desirable Experience Experience working with data from optical or QKD systems. Participation in collaborative research projects or standardsrelated work.