Anthony Leggett

Anthony James Leggett was born in Camberwell, south London, on 26 March 1938. In his Nobel autobiography he joked that he arrived on that date with only seven minutes to spare, an early sign of the procrastination he said marked his career. His father's forebears were village cobblers in Hampshire, and his grandfather became a greengrocer; his mother's parents were of Irish descent. His parents, Richard Leggett and Winifred Leggett (née Regan), met as students at the Institute of Education in London and both became teachers.

He was the eldest of five children, followed by sisters Clare and Judith and brothers Terence and Paul, all raised as Catholics, which he later said made them members of a small and somewhat embattled minority in England. Soon after his birth the family bought a house in Upper Norwood, but when war broke out he was evacuated to Englefield Green in Surrey, on the edge of Windsor Great Park, where he remembered barrage balloons over the Thames and lying awake listening to German flying bombs. After the war the family returned to Upper Norwood, and around 1949 they moved to a large, rambling house in Staines when his father took a teaching post at Beaumont College. As a boy he wanted to be an explorer, dug enormous holes in the front garden and took long solitary hikes and bike rides into the countryside.

After passing the eleven-plus early, Leggett attended the College of the Sacred Heart in Wimbledon and then Beaumont College, a Jesuit school near Windsor, where his father's terms of employment allowed the three Leggett boys to study free of charge. At 13 he was channelled into classics. In his final months at school a retired priest, Fr. Charles O'Hara, gave him informal lessons in modern mathematics, an experience that later gave him the confidence to switch to physics.

He won a scholarship to Balliol College, Oxford, in December 1954, went up in October 1955 and took a first class degree in Literae Humaniores (Greats) in 1959. He then took a second undergraduate degree in physics at Merton College, supported by a Domus scholarship and tutored by Michael Baker and David Brink, and despite a near disastrous first exam paper he was awarded a first. From 1961 he did doctoral research on liquid helium under Dirk ter Haar, held a Prize Fellowship at Magdalen College from 1963 to 1967 and completed his DPhil in 1964. Oxford later awarded him an honorary DLitt in 2005.

Leggett spent August 1964 to August 1965 as a postdoctoral fellow in David Pines's group at the University of Illinois Urbana-Champaign, where he produced his first internationally noticed work, on Fermi liquid effects in superfluid helium-3. He then spent a year with Takeo Matsubara at Kyoto University, where he wrote a paper on two-band superconductors that later proved important, followed by a roving year at Oxford, Harvard and Illinois.

In 1967 he became a lecturer at the University of Sussex, later reader and, from 1978, professor. After the experimental discovery of superfluid helium-3 in 1972, he developed between 1972 and 1975 the theory that explained its phases through anisotropic pairing of helium-3 atoms and a novel form of spontaneous symmetry breaking. He also spent time at the University of Tokyo and made two teaching visits to the university in Kumasi, Ghana, in 1976 and 1977.

In 1982 Illinois offered him the newly endowed MacArthur Chair, and after an eight month stay at Cornell he arrived in Urbana in autumn 1983. There he worked on glasses, high temperature superconductivity, atomic Bose-Einstein condensates and the limits of quantum mechanics at macroscopic scales. His work with collaborators on quantum dissipation and macroscopic quantum tunnelling guided experiments on superconducting circuits that underpin today's quantum computing research. From 2006 to 2016 he also held a position at the Institute for Quantum Computing in Waterloo, Canada, and in 2013 he became founding director of the Shanghai Center for Complex Physics at Shanghai Jiao Tong University. He retired from teaching at Illinois in 2018 (some obituaries give 2019) but continued as chief scientist of the Institute for Condensed Matter Theory, renamed the Anthony J. Leggett Institute for Condensed Matter Theory in 2023.

Leggett met Haruko Kinase while she was an undergraduate at Sussex studying international relations. His Nobel autobiography dates their marriage to June 1972, while the University of Illinois and The Guardian give 1973. They spent an extended honeymoon in Tokyo, living with Haruko's parents. In 1975 they bought a small house in central Brighton, and their daughter, Asako, was born there in September 1978. Haruko later earned a PhD in cultural anthropology at Illinois and researched the hospice system; Asako graduated from Illinois in geography and chemistry. Leggett and his daughter became US citizens in summer 2002, keeping British citizenship.

He spoke Japanese with reasonable fluency and kept lifelong friendships from Oxford, many with people from south and east Asia. Mountaineering, which he discovered on a course in Snowdonia as a teenager, was a lifelong passion. At Oxford he coxed the Balliol first eight, and as a teenager he was picked to play chess for England in the under 16 Glorney Cup. He and Haruko were known for opening their Urbana home to generations of students, postdocs and colleagues.

Leggett stopped practising Catholicism in his early twenties but wondered whether defending minority beliefs as a child had shaped what colleagues saw as an iconoclastic streak in his physics. He credited his Oxford philosophy training with shaping how he looked at the problems of physics.

He was openly sceptical that quantum mechanics is the final word at everyday scales. He believed the theory might be incomplete because of the quantum measurement problem, and in 2005 he debated fellow Nobel laureate Norman Ramsey at a Berkeley conference, arguing that attempts to test and possibly modify quantum theory were justified. He advised young researchers that no piece of honestly conducted research is ever wasted, and insisted that his own graduate students teach for at least one semester a year.

Leggett's theory of superfluid helium-3 became the cornerstone of the field and found uses in areas from cosmology to particle physics and liquid crystals, a point the Nobel committee stressed. His proposal for testing the symmetry of high temperature superconductors led to the 1993 Illinois experiment by Dale Van Harlingen, Donald Ginsberg and David Wollman that established their d-wave character. His theoretical work on macroscopic quantum tunnelling and coherence directly led to the experiments by John Clarke, John Martinis and Michel Devoret that won the 2025 Nobel Prize in Physics, and to the superconducting qubits used in quantum computing. The University of Illinois renamed its Institute for Condensed Matter Theory the Anthony J. Leggett Institute for Condensed Matter Theory in 2023.

Nobel Prize in Physics (2003, shared with Alexei Abrikosov and Vitaly Ginzburg) for pioneering contributions to the theory of superconductors and superfluids. Knight Commander of the Order of the British Empire (KBE) in the 2004 Birthday Honours, for services to physics. Wolf Prize in Physics (2002/2003, shared with Bertrand Halperin). Eugene Feenberg Memorial Medal (1999). Paul Dirac Medal and Prize (dated 1991 by the University of Illinois and 1992 by The Guardian). Simon Memorial Prize (1981). Fritz London Memorial Award (1981). Maxwell Medal and Prize (1975). Fellow of the Royal Society (1980), Fellow of the American Physical Society (1985), Honorary Fellow of the Institute of Physics (1998) and Foreign Fellow of the Indian National Science Academy (2011). Member of the US National Academy of Sciences, the American Philosophical Society and the American Academy of Arts and Sciences, and a foreign member of the Russian Academy of Sciences. Honorary DLitt from the University of Oxford (2005).

Leggett's Nobel lecture was titled "Superfluid 3-He: The Early Days as Seen by a Theorist," and he gave versions of it at venues including Kyoto University. He recorded long lecture series for the Institute for Quantum Computing in Waterloo, spoke at the Perimeter Institute and the Global Young Scientists Summit in Singapore, and gave lengthy interviews late in life to the UIUC Talkshow and the Illinois Physics podcast, in which he discussed superconductors, philosophy, teaching abroad and why young physicists should be wary of quantum foundations as a career.

Leggett died at his home in Urbana, Illinois, on 8 March 2026, at the age of 87. The University of Illinois announced his death on 9 March 2026, and tributes followed from the Nobel Prize, Oxford Physics, the Grainger College of Engineering and colleagues worldwide, with obituaries in The New York Times, The Guardian and Nature. The cause of death was not made public. He was survived by his wife, Haruko Kinase-Leggett, his daughter, Elizabeth Asako Kinase-Leggett, and his sisters, Judith Leggett and Clare Prangley.