Paul Adrien Maurice Dirac , OM ( August 8 , 1902 in Bristol â `` October 20 , 1984 in Tallahassee ) was an English physicist . Paul Adrien Maurice Dirac , OM , FRS ( ; 8 August 1902 â `` 20 October 1984 ) was an English theoretical physicist who made fundamental contributions to the early development of both quantum mechanics and quantum electrodynamics .