A Cardiff schoolboy
Brian David Josephson was born in Cardiff, Wales, on January 4, 1940, to Jewish parents, Abraham Josephson and Mimi Josephson, née Weisbard. He went to Cardiff High School, where the physics master, Emrys Jones, introduced him to theoretical physics and set him on the path of his life.
In 1957 he went up to Trinity College, Cambridge, to read mathematics. After two years he found pure mathematics somewhat sterile and switched to physics, graduating in 1960. He soon had a reputation as a brilliant, shy student. An examiner, the physicist Nicholas Kurti, was remembered saying that he seemed to go through the theory like a knife through butter. The American theorist Philip Anderson, who taught in Cambridge in 1961 and 1962, recalled that having Josephson in a class was a challenge, because everything had to be right or he would come up afterwards and explain the mistake.
A prediction at 22
Josephson began research for a doctorate under Brian Pippard at the Cavendish Laboratory, working on superconductors, metals that lose all electrical resistance when cooled close to absolute zero. A few years earlier, the BCS theory of John Bardeen, Leon Cooper and Robert Schrieffer had explained superconductivity as the result of electrons binding into pairs that move together in a single quantum state. Experimenters had also begun studying what happens when two superconductors are separated by a very thin layer of insulator, through which electrons can pass by quantum tunnelling.
In 1962, aged 22, Josephson worked out something no one had expected. He predicted that the electron pairs themselves could tunnel through the barrier, so that a supercurrent would flow from one superconductor to the other with no voltage at all. And if a steady voltage were applied across the junction, the current would not simply stop: it would oscillate at a very high frequency set only by the voltage and by fundamental constants of nature. His paper, “Possible new effects in superconductive tunnelling,” was received by the journal Physics Letters on June 8, 1962, and published on July 1.
The idea met resistance. John Bardeen, the most authoritative figure in the field, argued in print that there could be no such flow, and the two debated the question, civilly, at a conference in London that September. The experiment settled it. In January 1963 Philip Anderson and John Rowell at Bell Laboratories reported the first observation of the effect, and further experiments soon confirmed Josephson’s predictions in detail. Devices built on it are now called Josephson junctions.
Measuring the faintest magnetic fields
The Josephson effect is exquisitely sensitive to magnetic fields, and that made possible the SQUID, or superconducting quantum interference device, in which two Josephson junctions are joined in a ring. SQUIDs are the most sensitive magnetic sensors ever made, able to detect fields billions of times weaker than the Earth’s.
Their most important human use is in magnetoencephalography, or MEG, which records the tiny magnetic fields produced by electrical activity in the brain. Arrays of SQUIDs are the most common sensors in MEG machines. Doctors use MEG to locate the source of seizures in patients with epilepsy and to map the brain areas that control movement and speech before surgery, so that surgeons can avoid damaging them. SQUIDs are also used in geology, materials science and the search for minerals.
Defining the volt
The second great application comes from the precise link Josephson found between voltage and frequency. Because frequency can be measured with extraordinary accuracy using atomic clocks, a Josephson junction driven by microwaves produces a voltage that depends only on the frequency and on fundamental constants, not on the materials or the manufacturer. From 1972 the United States’ national standards laboratory began using the Josephson effect to maintain the volt, replacing banks of chemical cells.
Modern Josephson voltage standards link tens of thousands of junctions on a single chip and can produce precise voltages of up to ten volts, agreeing with one another to better than one part in ten billion. Since the redefinition of the international system of units in May 2019, Josephson standards have been the authoritative way of realising the volt. Every calibrated voltmeter, and so much of the world’s electrical measurement, traces back to them.
Building blocks of quantum computers
Josephson junctions have also become the basic building block of one of the leading kinds of quantum computer. In superconducting qubits, such as the transmon, a junction acts as a special, non-linear circuit element that turns an electrical circuit into an artificial atom with distinct quantum energy levels. In 1984 and 1985 John Clarke, Michel Devoret and John Martinis used a Josephson junction circuit to show that an object big enough to hold in the hand could behave quantum mechanically; that work, recognised with the Nobel Prize in Physics in 2025, laid the foundation for today’s superconducting quantum processors.
Josephson junctions are also used in superconducting digital electronics, in which each switch of a junction produces a single quantum of magnetic flux, and in superconducting cameras and detectors used in astronomy.
Cambridge career and Nobel Prize
Josephson was elected a Fellow of Trinity College in 1962, while still a student, and completed his PhD in 1964. After a year as a research assistant professor at the University of Illinois, he returned to Cambridge in 1967 as assistant director of research at the Cavendish Laboratory, became a Reader in 1972 and Professor of Physics in 1974, a post he held until he retired in 2007. He was elected a Fellow of the Royal Society in 1970.
In 1973, at the age of 33, he received half of the Nobel Prize in Physics for his theoretical predictions of the properties of a supercurrent through a tunnel barrier; the other half went to Leo Esaki and Ivar Giaever for their experiments on tunnelling in semiconductors and superconductors.
An unorthodox mind
From the early 1970s Josephson’s interests turned in a direction that has made him a controversial figure. He took up Transcendental Meditation in 1971 and became interested in the relationship between mind and matter. He founded the Mind–Matter Unification Project at the Cavendish Laboratory to explore whether physics could account for consciousness and for phenomena such as telepathy, and in 1983 he gave a presentation on higher states of consciousness to a committee of the United States Congress.
He has also publicly supported cold fusion and the idea that water can retain a memory of substances once dissolved in it, a claim offered as an explanation for homeopathy. Most scientists reject these ideas, and colleagues including Philip Anderson have criticised his positions. In 2001, when he wrote in a Royal Mail booklet marking the Nobel centenary that Britain was at the forefront of research into telepathy, several physicists complained publicly. Josephson has argued that science should examine unpopular ideas on their evidence rather than dismiss them because they are unpopular. None of this has diminished the standing of his work on superconductivity, which is accepted by all.
Jewish roots and private life
Josephson was born to a Jewish family in Cardiff, which had a small but long-established Jewish community. His parents were both Jewish, and the Jewish Virtual Library lists him among Jewish Nobel laureates in physics. He has not written publicly about Jewish religious practice; his own spiritual interests have run toward meditation, and he has said that meditation led him to believe in a creator.
In 1976 he married Carol Olivier; they had one child. Carol died in 2025. Josephson remains an emeritus professor at Cambridge and a fellow of Trinity College. A plaque in his honour can be seen on the Mond Building in Cambridge.
Legacy
Few predictions by a student have had such practical consequences. The effect Josephson foresaw in 1962 now defines how the world measures voltage, lets doctors watch the brain at work and find the source of epileptic seizures, and supplies the essential component of superconducting quantum computers. Whatever one thinks of his later ventures, the Josephson junction is one of the quiet foundations of modern measurement and of the quantum technologies now being built.
Sources & further reading
Brian Josephson, Wikipedia · Josephson effect, Wikipedia · Programmable Josephson Voltage Standards and Arbitrary Waveform, NIST · Magnetoencephalography, Wikipedia · Press release: The Nobel Prize in Physics 2025, NobelPrize.org · Brian David Josephson, Jewish Virtual Library · Researched from the sources above and checked against them. Spotted an error? Tell us.
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