Wikipedia

John Hopfield

For his father, the Polish-American spectroscopist, seeJohn J. Hopfield (spectroscopist).

John Joseph Hopfield(born July 15, 1933)[1]is an American physicist andemeritusprofessor ofPrinceton University,most widely known for his study ofassociative neural networksin 1982. He is known for the development of theHopfield network.Previous to its invention, research in artificial intelligence (AI) was in a decay period orAI winter,Hopfield's work revitalized large-scale interest in this field.[2][3]

John Hopfield
Hopfield in 2016
Born
John Joseph Hopfield

(1933-07-15)July 15, 1933(age 91)
Chicago, Illinois,U.S.
EducationSwarthmore College(AB)
Cornell University(PhD)
Known forHopfield network
Modern Hopfield network
Hopfield dielectric
Polariton
Kinetic proofreading
Awards
Scientific career
FieldsPhysics
Molecular biology
Complex systems
Neuroscience
InstitutionsBell Labs
Princeton University
University of California, Berkeley
California Institute of Technology
ThesisA quantum-mechanical theory of the contribution of excitons to the complex dielectric constant of crystals(1958)
Doctoral advisorAlbert Overhauser
Doctoral studentsSteven Girvin
Gerald Mahan
Bertrand Halperin
David J. C. MacKay
José Onuchic
Terry Sejnowski
Erik Winfree
Li Zhaoping

In 2024 Hopfield, along withGeoffrey Hinton,was awarded theNobel Prize in Physicsfor their foundational contributions tomachine learning,particularly through their work onartificial neural networks.[4][2]He has been awarded various major physics awards for his work in multidisciplinary fields includingcondensed matter physics,statistical physicsandbiophysics.

Biography

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Early life and education

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John Joseph Hopfield was born in 1933 inChicago[1]to physicistsJohn Joseph Hopfield(born in Poland as Jan Józef Chmielewski) and Helen Hopfield (née Staff).[5][6]

Hopfield received aBachelor of Artswith a major in physics fromSwarthmore Collegein Pennsylvania in 1954 and aDoctor of Philosophyin physics fromCornell Universityin 1958.[1]His doctoral dissertation was titled "A quantum-mechanical theory of the contribution ofexcitonsto the complexdielectric constantof crystals ".[7]Hisdoctoral advisorwasAlbert Overhauser.[1]

Career

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He spent two years in the theory group atBell Laboratoriesworking on optical properties of semiconductors working withDavid Gilbert Thomas[8]and later on a quantitative model to describe the cooperative behavior ofhemoglobinin collaboration withRobert G. Shulman.[1][5][9]Subsequently he became a faculty member atUniversity of California, Berkeley(physics, 1961–1964),[2]Princeton University(physics, 1964–1980),[2]California Institute of Technology(Caltech, chemistry and biology, 1980–1997)[2]and again at Princeton (1997–),[2][1]where he is the Howard A. Prior Professor of Molecular Biology, emeritus.[10]

In 1976, he participated in a science short film on the structure of the hemoglobin, featuringLinus Pauling.[11]

From 1981 to 1983Richard Feynman,Carver Meadand Hopfield gave a one-year course at Caltech called "The Physics of Computation".[12][13]This collaboration inspired theComputation and Neural SystemsPhD program at Caltech in 1986, co-founded by Hopfield.[14][12]

His former PhD students includeGerald Mahan(PhD in 1964),[15]Bertrand Halperin(1965),[16]Steven Girvin(1977),[16]Terry Sejnowski(1978),[16]Erik Winfree(1998),[16]José Onuchic(1987),[16]Li Zhaoping(1990)[17]andDavid J. C. MacKay(1992).[16]

Work

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In his doctoral work of 1958, he wrote on the interaction ofexcitonsin crystals, coining the termpolaritonfor aquasiparticlethat appears insolid-state physics.[18][19]He wrote: "The polarization field 'particles' analogous tophotonswill be called 'polaritons'. "[19]His polariton model is sometimes known as theHopfield dielectric.[20]

From 1959 to 1963, Hopfield and David G. Thomas investigated the exciton structure ofcadmium sulfidefrom its reflection spectra. Their experiments and theoretical models allowed to understand the optical spectroscopy ofII-VI semiconductor compounds.[21]

Condensed matter physicistPhilip W. Andersonreported that John Hopfield was his "hidden collaborator" for his 1961–1970 works on theAnderson impurity modelwhich explained theKondo effect.Hopfield was not included as a co-author in the papers but Anderson admitted the importance of Hopfield's contribution in various of his writings.[22]

William C. Topp and Hopfield introduced the concept of norm-conservingpseudopotentialsin 1973.[23][24][25]

In 1974 he introduced a mechanism for error correction inbiochemical reactionsknown askinetic proofreadingto explain the accuracy ofDNA replication.[26][27]

Hopfield published his first paper in neuroscience in 1982, titled "Neural networks and physical systems with emergent collective computational abilities" where he introduced what is now known asHopfield network,a type of artificial network that can serve as acontent-addressable memory,made of binary neurons that can be 'on' or 'off'.[28][5]He extended his formalism to continuousactivation functionsin 1984.[29]The 1982 and 1984 papers represent his two most cited works.[10]Hopfield has said that the inspiration came from his knowledge ofspin glassesfrom his collaborations with P. W. Anderson.[30]

Together withDavid W. Tank,Hopfield developed a method in 1985–1986[31][32]for solving discrete optimization problems based on the continuous-time dynamics using a Hopfield network with continuous activation function. The optimization problem was encoded in the interaction parameters (weights) of the network. The effective temperature of the analog system was gradually decreased, as in global optimization withsimulated annealing.[33]

Hopfield is one of the pioneers of thecritical brain hypothesis,he was the first to link neural networks withself-organized criticalityin reference to theOlami–Feder–Christensen modelfor earthquakes in 1994.[34][35]In 1995, Hopfield and Andreas V. Herz showed that avalanches in neural activity follow power law distribution associated to earthquakes.[36][37]

The original Hopfield networks had a limited memory, this problem was addressed by Hopfield and Dimitry Krotov in 2016.[33][38]Large memory storage Hopfield networks are now known asmodern Hopfield networks.[39]

Views on artificial intelligence

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In March 2023, Hopfield signed an open letter titled "Pause Giant AI Experiments",calling for a pause on the training ofartificial intelligence(AI) systems more powerful thanGPT-4.The letter, signed by over 30,000 individuals including AI researchersYoshua BengioandStuart Russell,cited risks such as human obsolescence andsociety-wide loss of control.[40][41]

Upon being jointly awarded the 2024 Nobel Prize in Physics, Hopfield revealed he was very unnerved by recent advances in AI capabilities, and said "as a physicist, I'm very unnerved by something which has no control".[42]In a followup press conference in Princeton University, Hopfield compared AI withdiscovery of nuclear fission,which led tonuclear weaponsandnuclear power.[2]

Awards and honors

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The 1969 ceremony of theOliver E. Buckley Prizeof condensed matter physics.Luis Walter Alvarez(left) congratulatesDavid Gilbert Thomas(middle) and John Hopfield (right).

Hopfield received aSloan Research Fellowship[43]in 1962 and as his father, he received aGuggenheim Fellowship(1968).[44]Hopfield was elected as a member of theAmerican Physical Society(APS) in 1969,[45][46]a member of theNational Academy of Sciencesin 1973, a member of theAmerican Academy of Arts and Sciencesin 1975, and a member of theAmerican Philosophical Societyin 1988.[47][48][49]He was the President of the APS in 2006.[50]

In 1969 Hopfield andDavid Gilbert Thomaswere awarded theOliver E. Buckley Prizeof condensed matter physics by the APS "for their joint work combining theory and experiment which has advanced the understanding of the interaction of light with solids".[51]

In 1983 he was awarded the MacArthur Foundational Prize by theMacArthur Fellows Program.[52]In 1985, Hopfield received the Golden Plate Award of theAmerican Academy of Achievement[53]and theMax Delbruck Prizein Biophysics by the APS.[9]In 1988, he received theMichelson–Morley AwardbyCase Western Reserve University.[54]Hopfield received the Neural Networks Pioneer Award in 1997 by theInstitute of Electrical and Electronics Engineers(IEEE).[55]

Geoffrey E. Hinton (left) and Hopfield at 2024 Nobel Week

He was awarded theDirac Medalof theInternational Centre for Theoretical Physicsin 2001 "for important contributions in an impressively broad spectrum of scientific subjects"[56][57]including "an entirely different [collective] organizing principle inolfaction"and" a new principle in which neural function can take advantage of the temporal structure of the 'spiking' interneural communication ".[57]

Hopfield received theHarold Pender Awardin 2002 for his accomplishments incomputational neuroscienceandneural engineeringfrom theMoore School of Electrical Engineering,University of Pennsylvania.[58]He received theAlbert Einstein World Award of Sciencein 2005 in the field of life sciences.[59]In 2007, he gave theFritz London Memorial LectureatDuke University,titled "How Do We Think So Fast? From Neurons to Brain Computation".[60]Hopfield received theIEEE Frank Rosenblatt Awardin 2009 for his contributions in understanding information processing in biological systems.[61]In 2012 he was awarded theSwartz Prizeby theSociety for Neuroscience.[62]In 2019 he was awarded theBenjamin Franklin Medal in Physicsby theFranklin Institute,[63]and in 2022 he shared theBoltzmann Medalaward in statistical physics withDeepak Dhar.[64]

He was jointly awarded the 2024Nobel Prize in PhysicswithGeoffrey E. Hintonfor "foundational discoveries and inventions that enable machine learning with artificial neural networks".[65][66]

In 2025 he was awarded theQueen Elizabeth Prize for Engineeringjointly withYoshua Bengio,Bill Dally,Geoffrey E. Hinton,Yann LeCun,Jen-Hsun HuangandFei-Fei Lifor the development of modern machine learning.[67]

References

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  67. ^Queen Elizabeth Prize for Engineering 2025
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