John Stewart Bell (28 June 1928 – 1 October 1990) was an Irish physicist, and the originator of Bell's theorem, a significant theorem in quantum physics regarding hidden variable theories.
1.) Whitaker, Andrew (Sep 19, 2016). "1 - John Bell - The Irish Connection". Quantum Nonlocality and Reality: 50 Years of Bell's Theorem. Cambridge University Press. p. 8. ISBN 9781107104341. John Bell was certainly not interested in Protestantism as such – his wife Mary  has reported that he was an atheist most of his life.
2.) Quantum Reflections. Cambridge University Press. 2000. p. xi. ISBN 9780521630085. "By now, he was also a 'Protestant Atheist', which he remained all his life."