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Portrait of Brian D. Josephson
Photo: Brian Josephson, Released by Brian Josephson by email; taken from his homepage · CC BY 3.0 via Wikimedia Commons

Nobel Prize in Physics · 1973

Brian D. Josephson

At 22 he predicted how electron pairs tunnel between superconductors, giving the world an exact volt and ultra-sensitive magnetic sensors.

The Nobel citation: “for his theoretical predictions of the properties of a supercurrent through a tunnel barrier, in particular those phenomena which are generally known as the Josephson effects”
Born
January 4, 1940, Cardiff, United Kingdom
Shared with
Leo Esaki, Ivar Giaever
Affiliation at the time
University of Cambridge, United Kingdom

Physics prize

1973

Shared with 2 other laureates.

Age that year

33years

Born in 1940.

Sources cited

25

Fact-checked September 24, 2026.

  • He made his Nobel-winning prediction in 1962 as a 22-year-old PhD student. His lecturer Philip Anderson later wrote that the whole achievement was Josephson's own.
  • A Bell Labs patent lawyer judged his 1962 paper so complete that no one else would manage to patent any substantial part of the Josephson effect.
  • Still a student, he debated John Bardeen, already a Nobel laureate, over the effect at a 1962 conference in London. Experiments at Bell Labs backed Josephson the next year.
  • Since a 1990 international agreement, the world's voltage standards have rested on his effect, which turns a microwave frequency into an exactly known voltage.
  • The 2025 Nobel Prize in Physics honoured quantum experiments on the Josephson junction, the device named after him, which is now used to build experimental quantum computers.

The breakthrough

Predicting the Josephson effects: supercurrents that tunnel (1962)

Some metals, cooled to very low temperatures, become superconductors: electricity flows through them with no resistance at all. Inside, electrons pair up and move in lockstep, sharing one quantum wave with a single rhythm, called its phase. In 1960 Ivar Giaever showed that single electrons can 'tunnel' through a very thin insulating layer between two metals, something everyday physics forbids. In 1962 Josephson, a 22-year-old Cambridge student, worked out what happens when both sides are superconductors. His calculations showed that the electron pairs can tunnel too, almost as easily as single electrons. He predicted three effects. A current can flow across the barrier with no voltage at all, its size set by the difference in phase between the two sides. Apply a steady voltage, and the current instead swings back and forth at a frequency fixed only by that voltage and two constants of nature: about 484 billion cycles per second for every thousandth of a volt. And a magnetic field shifts the phases, so the current is extremely sensitive to magnetism. Picture two choirs singing the same note on either side of a thin wall. They stay in step through the wall, and how far out of step they are decides the flow. Push one choir slightly sharp with a voltage, and the two drift in and out of step at a beat rate that reveals the voltage exactly. Philip Anderson and John Rowell at Bell Labs confirmed the effect in 1963.[1],[3],[4],[7],[8],[15],[20]

“developments in laboratories over the world, which followed from asking one simple question, namely what is the physical significance of broken symmetry in superconductors?”
Brian D. Josephson, From the closing sentence of his Nobel Lecture, 'The Discovery of Tunnelling Supercurrents', Stockholm, 12 December 1973, reflecting on how much had grown from his student question.[3]

What it meant for humanity

Josephson's prediction became a set of tools for measuring the world with extraordinary precision. The first was a better volt. A Josephson junction turns a microwave frequency into an exactly known voltage, and frequencies can be controlled very accurately. By the late 1960s such measurements had exposed errors in the accepted values of fundamental constants, and standards laboratories began comparing voltages without shipping banks of standard cells, a kind of reference battery, between them. Since a 1990 international agreement, voltage standards worldwide have rested on the effect. Chips holding thousands of junctions now work in more than 70 national, industrial and military laboratories, where they calibrate the secondary references and precision voltmeters that other measurements depend on. Since 2019 the Josephson constant has an exact value in the international system of units. The second tool was the SQUID, a superconducting loop containing Josephson junctions that detects extremely faint magnetic fields. By 1973 SQUIDs were already used in ore prospecting, gravitational-wave searches and measurements of the fields around the heart and brain. Today helmets holding about 300 SQUID sensors record the brain's magnetic signals in magnetoencephalography (MEG), which helps doctors find where seizures begin and map vital brain areas before epilepsy surgery. SQUIDs also read out sensitive detectors in astronomy and dark-matter searches. The third use is still unfolding. Circuits of Josephson junctions can behave like single quantum objects, and they are one of the ways researchers build qubits, the basic units of quantum computers. In 2019 Google reported a 53-qubit processor built with Josephson junctions. Josephson himself noted that early hopes for Josephson-junction computers did not come off, but that the effect found more practical uses than he had expected.

  • Since a 1990 international agreement, voltage standards worldwide have been based on the Josephson effect, and Josephson array standards operate in more than 70 national, industrial and military laboratories.[14],[15]
  • By the late 1960s, measurements of the AC Josephson effect were precise enough to reveal errors in the accepted values of fundamental constants and to improve them.[3],[4]
  • In magnetoencephalography, helmets of about 300 SQUID sensors record the brain's magnetic fields, helping to locate where seizures start in people being assessed for epilepsy surgery.[17],[18]
  • The 2025 Nobel Prize in Physics went to John Clarke, Michel Devoret and John Martinis for 1984-85 experiments showing quantum tunnelling and quantised energy in a hand-sized Josephson junction circuit.[19],[20]
  • By 1973, the Nobel presentation speech noted, instruments built on his effects were already used to measure temperatures near absolute zero, prospect for ore, hunt for gravitational waves and study magnetic fields around the heart and brain.[5]
  • Google's 2019 Sycamore processor, made with Josephson junctions, ran 53 superconducting qubits through a sampling task in about 200 seconds that Google estimated would take a top supercomputer 10,000 years.[21]

Impact in numbers

Josephson's legacy lies mostly in measurement, and we record no numeric impact claims. His effects gave the world an exact, reproducible volt, used since 1990 by standards laboratories and, through them, in the calibration chains behind electrical measurement. They made SQUIDs possible, extremely sensitive magnetic sensors that serve brain imaging before epilepsy surgery, geophysical surveys and physics experiments. They also underlie superconducting qubits, one of the routes being explored toward quantum computing. Each of these is real, but none has a published total of lives saved, people helped or money earned that could fairly be credited to a 1962 theory, and long chains of experimenters, engineers and companies built the devices. MEG, for instance, adds information to epilepsy assessments alongside EEG, MRI and PET, so counting its patients would overstate its effect. Rather than invent a figure, we describe the impact in words.

Fundamental scienceTechnologyHealth

No number is given here on purpose. Some contributions cannot be counted honestly, and we would rather describe them than invent a figure.

The double edge

The physics Josephson predicted has caused little documented harm; the controversy is about his later career. From the early 1970s he practised Transcendental Meditation and turned to the mind, consciousness and the paranormal. He has argued that telepathy may be real, and he has defended water memory, a proposed explanation for homeopathy, and cold fusion, ideas that mainstream science rejects. Critics have cited him as an example of 'Nobel disease', a label for laureates who embrace ideas without scientific support. In 2001 he wrote in a Royal Mail stamp booklet marking the Nobel centenary that new physics might one day explain telepathy and that Britain was at the forefront of such research. The Oxford physicist David Deutsch called the claim rubbish. Josephson answers that scientists show 'pathological disbelief' toward unorthodox research. The technologies built on his work carry risks of their own. SQUIDs have been proposed for hunting submarines. Quantum computers, for which Josephson-junction circuits are one of the designs being pursued, could one day break the encryption that protects email, online shopping and national-security information. In 2024 the US standards agency NIST issued new encryption standards to guard against that threat.

  • Minor

    Promoting ideas that mainstream science rejects

    Josephson has argued that telepathy and other paranormal effects may be real and has supported water memory, offered as an explanation for homeopathy, and cold fusion. Physicists including Philip Anderson have criticised him since the 1970s. When his 2001 Royal Mail booklet text drew complaints from several physicists, David Deutsch said the Royal Mail had been fooled into backing nonsense. We found no documented case of direct harm from his advocacy.[12],[13],[25]

  • Minor

    Quantum computers and encryption

    Superconducting qubits built from Josephson junctions are one route to quantum computers. NIST warns that a sufficiently capable quantum computer could defeat the public-key encryption behind email, e-commerce and national-security communications, and some experts expect such a machine within a decade. This is a future risk, not a realised harm.[6],[20],[22]

  • Minor

    Military sensing

    SQUID magnetometers have been proposed as magnetic anomaly detectors on maritime patrol aircraft for anti-submarine warfare, and Josephson voltage standards also serve military calibration laboratories.[15],[16]

Against the odds

Josephson's story is not one of persecution, and it should not be told as one. His grandparents came to Britain from Russia. Between 1881 and 1914, pogroms, persecution and poverty drove a mass migration of Jews out of the Tsarist empire. Many settled in South Wales, and by 1918 about 6,000 Jews lived in Wales. They were largely accepted, and oral histories gathered from Welsh Jews record few memories of antisemitism. There were exceptions. In August 1911 crowds in Tredegar and other valley towns looted Jewish-owned shops and homes until Home Secretary Winston Churchill sent in troops; historians still argue over how far the riots were driven by antisemitism rather than economic anger. Josephson was born in Cardiff in 1940, the only child of a schoolteacher and a mother who taught and worked as a reporter. He grew up in the suburb of Pen-y-lan and won a Cambridge mathematics scholarship at 15. We found no record of antisemitism directed at him. The obstacles he faced were intellectual. As a student he had to defend his prediction against doubters, among them John Bardeen, until experiments confirmed it in 1963. Later, his research on the mind and the paranormal drew fierce criticism, which he regards as prejudice and says has cost him academic support.

  • —

    Other

    Both sets of grandparents immigrated from Russia, in an era when pogroms, persecution and hardship drove a mass Jewish migration from the Tsarist empire; his family's own reasons are not recorded. In 1911 anti-Jewish riots hit Tredegar and other South Wales towns.[11],[23],[24]

  • 1962

    Other

    As a 22-year-old student he had to defend his prediction against leading physicists, including John Bardeen, who argued in print that such a supercurrent could not exist. Josephson answered him at a London conference, and Bell Labs experiments confirmed the effect in 1963.[3],[7],[12]

  • 2010

    Other

    His work on the paranormal led the organiser of a 2010 conference on quantum theory to withdraw his invitation, which was reinstated after complaints. Josephson regards such criticism as prejudice that has deprived him of an academic support network.[12]

Jewish background

Both parents JewishRelationship to Jewish identity not documented

Josephson was born in Cardiff, the only child of Jewish parents. His father, Abraham Josephson, was a schoolteacher, born in Salford to David and Betsy Josephson, who had immigrated from Russia. His mother, Minnie 'Mimi' Josephson, née Weisbard, was born in Swansea to parents who had also come from Russia; she taught, worked as a reporter and wrote poetry, which her son later published. We found no public statement by Josephson about his own Jewish identity or religious upbringing. Since 1971 he has practised Transcendental Meditation, and he has said that meditation led him to believe in a creator.[11],[12]

Key dates

  1. January 4, 1940

    Born in Cardiff, Wales, the only child of Jewish parents, Abraham Josephson, a schoolteacher, and Mimi Josephson, née Weisbard.[1],[11]

  2. 1957

    Enters Trinity College, Cambridge, on a mathematics scholarship he had won at 15; he later switches to physics.[9],[11]

  3. 1960

    Graduates from Cambridge and begins research under Brian Pippard at the Royal Society Mond Laboratory.[2],[3]

  4. July 1962

    Publishes 'Possible new effects in superconductive tunnelling' in Physics Letters, predicting the Josephson effects. Elected a Fellow of Trinity College the same year.[2],[8]

  5. September 1962

    Debates John Bardeen, who doubted the effect, at the international low-temperature physics conference in London.[7],[12]

  6. 1963

    Philip Anderson and John Rowell at Bell Labs observe tunnelling supercurrents, confirming his prediction.[3],[7]

  7. 1964

    Awarded his PhD by the University of Cambridge.[2]

  8. 1967

    Returns to Cambridge as Assistant Director of Research after a year as a research assistant professor at the University of Illinois.[2],[9]

  9. 1970

    Elected a Fellow of the Royal Society.[9],[10]

  10. 1971

    Begins practising Transcendental Meditation and turns increasingly to the study of mind and consciousness.[12],[13]

  11. October 23, 1973

    Awarded half of the Nobel Prize in Physics at 33; Leo Esaki and Ivar Giaever share the other half.[1],[4]

  12. 1974

    Appointed Professor of Physics at Cambridge, a post he holds until he retires in 2007.[2],[9]

  13. 1990

    By international agreement, voltage standards worldwide are based on the Josephson effect.[14],[15]

  14. 2025

    The Nobel Prize in Physics goes to John Clarke, Michel Devoret and John Martinis for quantum experiments on Josephson junction circuits.[19],[20]

Sources

  1. 1.Brian D. Josephson – Facts · NobelPrize.org
  2. 2.Brian D. Josephson – Biographical · NobelPrize.org (from Nobel Lectures, Physics 1971-1980), 1973
  3. 3.The Discovery of Tunnelling Supercurrents (Nobel Lecture, 12 December 1973) · NobelPrize.org, 1973
  4. 4.The Nobel Prize in Physics 1973 – Press release · Royal Swedish Academy of Sciences / NobelPrize.org, 1973
  5. 5.The Nobel Prize in Physics 1973 – Award ceremony speech (Stig Lundqvist) · NobelPrize.org, 1973
  6. 6.Brian D. Josephson – Interview (Lindau, June 2004) · NobelPrize.org, 2004
  7. 7.How Josephson discovered his effect (Philip W. Anderson, Physics Today, November 1970) · Physics Today (archived copy), 1970
  8. 8.Possible new effects in superconductive tunnelling (Physics Letters 1, 251-253) · Physics Letters (Elsevier), 1962
  9. 9.Emeritus Professor Brian Josephson FRS · Department of Physics, University of Cambridge
  10. 10.Professor Brian Josephson FRS · The Royal Society
  11. 11.Brian Josephson – Nobel Prize winner · Roath Local History Society, 2021
  12. 12.Brian Josephson · Wikipedia
  13. 13.Pioneer of the paranormal (Edwin Cartlidge, Physics World, May 2002; reprinted on Josephson's university page) · Physics World / University of Cambridge, 2002
  14. 14.Ampere: The Quantum Metrology Triangle · National Institute of Standards and Technology (NIST)
  15. 15.Josephson voltage standard · Wikipedia
  16. 16.SQUID · Wikipedia
  17. 17.Magnetoencephalography · Wikipedia
  18. 18.Clinical Utility of Magnetoencephalography in Epilepsy Evaluation: A Qualitative Systematic Review (Kim et al., J Epilepsy Res 15:83-92) · Korean Epilepsy Society / PubMed Central, 2025
  19. 19.The Nobel Prize in Physics 2025 – Press release · Royal Swedish Academy of Sciences / NobelPrize.org, 2025
  20. 20.The Nobel Prize in Physics 2025 – Popular science background · Royal Swedish Academy of Sciences / NobelPrize.org, 2025
  21. 21.Quantum supremacy using a programmable superconducting processor (Arute et al., Nature 574, 505-510) · Nature, 2019
  22. 22.NIST Releases First 3 Finalized Post-Quantum Encryption Standards · National Institute of Standards and Technology (NIST), 2024
  23. 23.History debate over anti-Semitism in 1911 Tredegar riot · BBC News, 2011
  24. 24.The forgotten stories of the Jews leaving Wales after a century · WalesOnline, 2019
  25. 25.Royal Mail's Nobel guru in telepathy row (Robin McKie, The Observer, 30 September 2001) · The Guardian / The Observer, 2001

Fact-checked on September 24, 2026 by a separate AI fact-checking pass that re-opened the sources, with 3 corrections made. How we check

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