As a graduate student at Columbia University in New York in the late 1960s and early 1970s, he discovered several of the most important ideas in quantum information theory, including quantum money (which led to quantum key distribution), quantum multiplexing (the earliest example of oblivious transfer) and superdense coding (the first and most basic example of entanglement-assisted communication).  Although this work remained unpublished for over a decade, it circulated widely enough in manuscript form to stimulate the emergence of quantum information science in the 1980s and 1990s. https://en.wikipedia.org/wiki/Stephen_Wiesner