Hugh Everett III was a groundbreaking American physicist and mathematician in the field of quantum mechanics, and a noted atheist.
Although Everett studied at a Catholic University, he was a long-standing atheist; even claiming to have scientifically disproved the Christian religion. Although he was an atheist, he proposed the many-worlds interpretation of quantum mechanics, believing it ensured immortality for all humans.
Everett was a great asset to quantum mechanics, although he was not recognized widely until after his death in 1982. He published The Many-Worlds Interpretation of Quantum Mechanics in 1973 -- his one and only publication. Little of his work was recognized until Bryce DeWitt wrote an article for Physics Today discussing Everett's relative-state theory. Everett is widely regarded as an important figure for the inflation of scientific interest in quantum mechanics.
1.) "Everett was a life-long atheist, but he did not let that stand in his way as St. John's was well-regarded academically and socially." Peter Byrne, The Many Worlds of Hugh Everett III: Multiple Universes, Mutual Assured Destruction, and the Meltdown of a Nuclear Family (2010), page 29.