John Stewart Bell, Quantum Information and Quantum Information Theory

Andrew Charles Whitaker

Abstract John Stewart Bell was one of the most significant physicists of the twentieth century; his work has led to a much enhanced understanding of quantum theory and what it says about the physical universe, particularly about realism, determinism, and locality. This book describes Bell's relatively humble origins and his struggles to obtain secondary and university education. It then describes his work at Harwell, where he made important theoretical contributions to the development of particle accelerators, in particular with his pioneering work on strong focussing. Later, he proved the extremely important CPT theorem. At CERN, Bell made a range of important theoretical contributions to elementary particle physics; these contributions include the physics of neutrinos, the existence of different types of neutrinos, the suitability of gauge theory for all physical interactions, and the Adler–Bell–Jackiw anomaly, which shows how classical symmetries are lost under quantum theory. In his work on quantum theory, he criticized the orthodox 'Copenhagen' interpretation of quantum theory, which did not allow the actual state of the physical world to be analysed. He showed that the famous von Neumann theorem, which claimed to show that 'hidden variables' were not allowed in quantum theory, was incorrect; his famous Bell's theorem, or Bell's inequality, showed that any such variables much be non-local. Bell's work led to greatly increased freedom in the discussion of quantum theory, and the development of quantum information theory.

Michael A. Nielsen, Isaac L. Chuang

Charles H. Bennett, Peter W. Shor

Andrew Whitaker

John Stewart Bell (1928-1990) was one of the most important figures in twentieth-century physics, famous for his work on the fundamental aspects of the century's most important theory, quantum mechanics. While the debate over quantum theory between the supremely famous physicists, Albert Einstein and Niels Bohr, appeared to have become sterile in the 1930s, Bell was able to revive it and to make crucial advances - Bell's Theorem or Bell's Inequalities. He was able to demonstrate a contradiction between quantum theory and essential elements of pre-quantum theory - locality and causality. The book gives a non-mathematical account of Bell's relatively impoverished upbringing in Belfast and his education. It describes his major contributions to quantum theory, but also his important work in the physics of accelerators, and nuclear and elementary particle physics.

Philip George Burke, Ian Colin Percival

John Stewart Bell, the second of four children of John and Annie Bell (née Brownlee), was born in Belfast on 28 July 1928. The families of both his parents were Protestant, his father's family coming from Fermanagh and his mother's from Tyrone. Originally, Annie Bell's family had come from Scotland and John Bell's second Christian name was that of her family. At home, John Bell was always known as Stewart, only becoming John when he went to university. John Bell's family were not well off, his father being sent out to work before he was twelve years old to help the family finances. However, John Bell's father and mother always impressed on John, his elder sister Ruby and his two younger brothers David and Robert the importance of education. Later, David, through evening study, became a qualified electrical engineer and a professor at Lambton College in Canada, writing several very successful textbooks; Robert is now a successful Northern Ireland businessman.

Dan Cristian Marinescu, Gabriela M. Marinescu