Josephson, Brian David (1940-) is a Welsh physicist who received the 1973 Nobel Prize in physics for his discovery of the Josephson effect, which describes the unusual behavior that may occur when electrons “tunnel” through a barrier between two superconductors. Josephson shared the Nobel Prize with physicists Leo Esaki and Ivar Giaever, whose earlier discoveries in superconductivity were the basis for Josephson's findings.
After graduating from Cardiff High School, Josephson enrolled at Trinity College, Cambridge University, in England, where he received his B.A. degree in 1960 and his M.A. and Ph.D. degrees in physics in 1964. From 1962 until 1969, he was also a junior research fellow at Trinity College.
Josephson's exceptionally deep grasp of physics made him a brilliant and self-confident student, and he made his own first important discovery while still an undergraduate. That work, published in 1960, was a prediction related to the Mössbauer effect, a physical phenomenon giving rise to photons of extremely precise wavelengths. In the late 1950's, German physicist Rudolf Ludwig Mössbauer's extremely sensitive technique was being used to test a prediction of Albert Einstein's theory of general relativity—the gravitational red shift—which states that the color of light emitted by any matter is altered by the gravitational field at the source.
Josephson realized that researchers using the Mössbauer effect had been overlooking a crucial factor related to temperature and therefore arriving at erroneous results. In light of Josephson's findings, physicists working on this problem were forced to “go back to the drawing board,” for his calculations showed that even extremely small temperature differences between the atoms sending the light and those detecting it could substantially affect the outcome of the red-shift experiment. This contribution made Josephson's early reputation, while he was still in his early 20's.
In graduate school, Josephson became particularly interested in superconductivity, the phenomenon in which the electrical resistance in metals and other conductors completely disappears when they are cooled to extremely low temperatures. Through this effect, such materials become superconductors capable of an uninterrupted “frictionless flow” as long as they remain below the critical temperature.
In 1962, building on a foundation of work done earlier on the tunneling effect in materials by Esaki and Giaever, Josephson began to work out a related problem. Tunneling describes the ability of waves to penetrate barriers and appear on the other side, and the new science of quantum mechanics predicted for the first time that not only light but matter too had wave properties.
The question of whether matter such as electrons could actually behave as predicted and exhibit tunneling was controversial, however. Superconductivity became the context in which this possibility was first tested, because experiments could be carried out in superconductors where electrons were known to join together into waves composed of billions of electron pairs (supercurrents of Cooper pairs), expanding quantum effects from the microscopic atom to large samples in which effects could be measured with simple laboratory tools. Giaever had earlier found that small electric currents could pass between a normal conductor and a superconductor separated by a thin nonconducting barrier, providing evidence of tunneling of matter.
But it was Josephson who fully analyzed the situation of two superconducting regions separated by a thin barrier, leading to extremely surprising predictions. He realized that two superconducting regions, close together but not touching, would generate currents in between, in what is now known as the “Josephson junction,” whenever the macroscopic wave functions overlapped—and even though no current could be found within this junction. Moreover, his calculations predicted what is now known as the DC Josephson effect—that a supercurrent should flow through this barrier even if no voltage (pressure) were applied. Rapidly oscillating supereurrents were predicted to accompany a nonzero voltage across the barrier, known as the AC Josephson effect. Additionally, he found that the frequency of these oscillating currents that flowed under a voltage were completely independent of the properties of the materials involved, and instead involved only universal constants such as Max Karl Ernst Ludwig Planck's constant. Thus the AC Josephson effect could be used to measure fundamental constants of nature and to verify fundamental realities of the quantum world.
The results of these calculations surprised even Josephson and were strongly disputed by prestigious theorists who did not accept that the Cooper pairs could penetrate a barrier. Once he had calculated this tunneling effect, Josephson tried to observe its occurrence himself to confirm his theory, but his skills as an experimenter were not equal to his theoretical ability. Soon thereafter, however, tests performed by J. M. Rowell, Philip Warren Anderson, and S. Shapiro all gave conclusive evidence of the existence of the phenomenon now known as the Josephson effect.
The confirmation of this phenomenon had a revolutionary impact not only for basic quantum physics but also in potentially useful technological applications. By 1980, IBM Corporation had applied Josephson's discoveries to successfully demonstrate a new type of computer element capable of operating at speeds between 10 and 100 times as fast as ordinary silicon chips. Although superconducting computing devices have yet to be fully utilized, other uses of Josephson junctions have been. One such apparatus is known as the SQUID, or superconducting quantum interference device. SQUID's are used as extremely sensitive devices for measuring small magnetic fields. They have been used for the detection of subtle geophysical anomalies in the magnetic field and even to sense the tiny magnetic fields produced by the human brain. The Josephson effect also provided a new way to generate microwave radiation of precisely known wavelengths.
Aside from his year as a visiting research professor at the University of Illinois from 1965 through 1966, Josephson has remained at Cambridge. Upon his return to the university from America, he became assistant director of research there and in 1974, after receiving his Nobel Prize, was appointed professor of physics. He was elected to the Royal Academy of Sciences in 1970.
Josephson continued to do research in super-conductivity in the years after his discovery and became especially interested in studying the occurrence of critical “phase transitions,” phenomena such as the transition from a gaseous to a fluid state, or similar transitions in materials capable of both normal conductivity and superconductivity.
In the late 1960's, Josephson's work led him to see potential connections between quantum effects in physics and consciousness, and a theorem produced by theoretical physicist John Bell particularly influenced him. Bell has postulated that, despite how far apart they may be in the universe, any two objects obtained from a larger source will always be influenced by one another.
Feeling constrained in his search for further breakthrough truths by the laws of conventional physics, Josephson began to expand his studies into other avenues, including psycholinguistic theory, music, the nature of intelligence, and more recently, ertificial intelligence. In 1971, he became a practitioner of Transcendental Meditation (TM), a mental technique introduced to the western world by Maharishi Mahesh Yogi. Josephson was drawn by the seeming parallels between quantum behavior and explanations of consciousness and perception that were proposed by the Maharishi.
Josephson continued to attempt to combine computation and theories of information to seek new avenues for scientific explanation. His reasoning is that consciousness itself, and the effects of the observer upon any observed phenomenon, may also some day by explained in the single unifying light of quantum theory. Josephson has also conjectured on the possibility that life is based upon some form of self-organizing principles that reflect certain quantum mechanical effects. Although Josephson's work outside of traditional physics has been controversial among fellow scientists, he has been courageous in approaching phenomena, both in physics and the larger scientific world, beyond the usual barriers of understanding.
In 1978, Josephson attended an international symposium on consciousness at Oxford and in 1980, in collaboration with V. S. Ramachandran, edited and published transcripts of those proceedings under the title Consciousness and the Physical World. He also began, in the 1990's, to study music as a symbol system, drawing parallels in published papers between DNA (deoxyri-bonucleic acid) and music as two examples of such information systems.
As a physicist, Josephson is interested in paranormal occurrences and the interactions between mind and matter as expressions of quantum mechanics, the first theory in physics that necessarily takes into consideration the role of the observer. To further these studies, he established and is the director of the Mind-Matter Unification Project, which operates under the auspices of the Theory of Condensed Matter Group at Cambridge's world-renowned Cavendish Laboratory.