Richard Feynman

Richard Feynman (1918 to 1988) was the American theoretical physicist who helped build quantum electrodynamics, the quantum theory of light and matter, and who introduced the path integral formulation of quantum mechanics. He is also credited with an early proposal, made in 1981, that quantum systems could be simulated efficiently only by a quantum computer, an idea often cited as an origin of quantum computing. He shared the Nobel Prize in Physics for 1965.

#Quantum electrodynamics

Feynman, independently with Julian Schwinger and Shin'ichiro Tomonaga, developed a consistent theory of how charged particles and light interact, resolving the infinities that had plagued earlier attempts. His diagrammatic method, now called Feynman diagrams, made the calculations tractable and became standard across particle physics. The three shared the 1965 prize "for their fundamental work in quantum electrodynamics, with deep-ploughing consequences for the physics of elementary particles" (Nobel Prize facts). Quantum electrodynamics is the founding example of a relativistic quantum field theory.

#The path integral formulation

In 1948 Feynman recast quantum mechanics in terms of a sum over all possible paths a system can take between two points, each path contributing a phase (Feynman 1948). This path integral formulation is mathematically equivalent to the earlier matrix and wave approaches of Heisenberg and Schrodinger, but it offers a distinctive picture, especially clear in the double-slit experiment, where the interference pattern arises from summing contributions of every path through the slits. The method is now central to quantum field theory and statistical physics.

#Proposing the quantum computer

At a 1981 conference on the physics of computation, later published in 1982, Feynman observed that simulating quantum systems on ordinary computers appears to require resources that grow exponentially with system size (Feynman 1982). He suggested that a computer built from quantum elements could carry out such simulations naturally. This proposal, alongside contemporaneous work by others, is widely regarded as a starting point for quantum computing and for the goal of demonstrating a quantum advantage over classical machines.

#Significance

Feynman's contributions span the history of quantum theory from its mature field-theory phase to the birth of quantum information. His diagrams and path integral remain everyday tools of physics, and his simulation idea helped launch a field that now motivates much of quantum hardware research. He was also a noted teacher, whose Feynman Lectures on Physics remain widely read.

#History

Feynman was born in New York in 1918 and completed his doctorate at Princeton in 1942 (Nobel biographical). He worked on the Manhattan Project at Los Alamos during the Second World War, then held positions at Cornell and, from 1950, at the California Institute of Technology. In 1986 he served on the commission investigating the Challenger space shuttle accident. He died in 1988.