John Hopfield (Photo – Courtesy of John Hopfield )
Caltech professor emeritus John Hopfield has been awarded the Nobel Prize in Physics along with Geoffrey Hinton of the University of Toronto “for foundational discoveries and inventions that enable machine learning with artificial neural networks,” according to the award citation.
By Whitney Clavin, Caltech
Hopfield, who is currently a professor of molecular biology at Princeton University, served as a professor of chemistry and biology at Caltech from 1980 to 1996 and is currently the Roscoe G. Dickinson Professor of Chemistry and Biology, Emeritus at Caltech. He co-founded Caltech’s Department of Computation and Neural Systems in 1986.
“John moved from Bell Labs and Princeton, where he studied physics, to Caltech’s chemistry and chemical engineering and biology departments for a joint appointment in 1980,” says Peter Dervan, Bren Professor of Chemistry, Emeritus, at Caltech. “He was interested in building a model of how the brain works and became renowned for his model of neural networks. He was our beloved colleague for 17 years until 1996 when he returned to Princeton.”
Today’s machine learning, or artificial intelligence (AI), tools—such as ChatGPT and other programs that can assemble information and seemingly converse with humans—have roots in Hopfield’s pioneering work on artificial neural networks. In the early 1980s, Hopfield merged his background in physics with neurobiology to create a simple computer model that behaved less like the computers of that time and more like the human brain.
According to the Nobel Prize committee’s popular summary of the prize work, Hopfield’s research interests “had taken him outside the areas in which his colleagues in physics worked,” leading him to move across the continent to Caltech. “There, he had access to computer resources that he could use for free experimentation and to develop his ideas about neural networks,” the committee wrote.
Referred to as the Hopfield network, his computer model mimics the architecture of the human brain to store information. The Hopfield network consists of nodes that are connected to each other like neurons in the human brain; the connections between nodes can be made stronger or weaker, such that the strong connections form memories.
Shortly after joining the Caltech faculty, Hopfield teamed up with the late physicist Richard Feynman and with Carver Mead (BS ’56, PhD ’60), the Gordon and Betty Moore Professor of Engineering and Applied Science, Emeritus, to co-teach a yearlong course called “The Physics of Computation.” The course was intended to unite their respective fields to explore the relationship between nanoscale physics, computation, and brain function. Three years later, the class evolved into a new interdivisional program at Caltech called Computation and Neural Systems (CNS), a vibrant community of scholars that includes dozens of faculty and has produced more than 100 PhDs.
As an educator and a researcher, Hopfield exemplified Caltech’s commitment to curiosity-driven science and to encouraging and supporting faculty to pursue areas of interest at the intersection of fields, recalls Harry Gray, the Arnold O. Beckman Professor of Chemistry and founding director of the Beckman Institute. “We were successful in recruiting him to join forces with Caltech in chemistry and biology, and his work here led to Nobel recognition.”
Though Hopfield was a theorist, says Rudy Marcus, Caltech’s John G. Kirkwood and Arthur A. Noyes Professor of Chemistry and himself a Nobel laureate, there were times when he acted like an experimentalist. “As one example of his ingenuity, I recall that he once used his physics background to locate an underground leak in a water pipe at his house and repair it,” says Marcus. “It impressed me at the time, since this was far beyond my skills.”
Hopfield was born in 1933 in Chicago. He earned his bachelor’s degree from Swarthmore College in 1954 and his PhD from Cornell University in 1958. He has received numerous awards, including the Boltzmann Medal (2022), the Benjamin Franklin Medal in Physics (2019), the Albert Einstein Award (2005), the Dirac Medal of the International Centre for Theoretical Physics (2001), and the MacArthur Fellowship (1983–1988).
Hopfield’s Nobel Prize is the 48th awarded to Caltech faculty, alumni, and postdoctoral scholars.
This article has been edited for brevity and clarity. Read the full article at this link.
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