Daniel Frank Walls
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13 September 1942|
Napier, New Zealand
|Died||12 May 1999
Auckland, New Zealand
|Institutions||University of Auckland
University of Waikato
|Alma mater||University of Auckland
|Doctoral advisor||Roy J. Glauber|
|Doctoral students||Gerard J. Milburn
Andrew C. Doherty
Howard J. Carmichael
Peter D. Drummond
Craig M. Savage
|Known for||Quantum optics|
|Notable awards||Einstein Prize for Laser Science (1990)
Dirac Medal (1995)
Daniel Frank Walls (13 September 1942 – 12 May 1999) was a New Zealand theoretical physicist specialising in quantum optics.
Walls gained a BSc in physics and mathematics and a first class honours MSc in physics at the University of Auckland. He then went to Harvard as a Fulbright Scholar, obtaining his PhD in 1969, under Roy J. Glauber (who later won a Nobel prize). After holding post-doctoral positions in Auckland and Stuttgart, Walls became a senior lecturer in physics at the University of Waikato in 1972, where he became professor in 1980. In 1987 he moved to the University of Auckland as professor of theoretical physics.
His major research interests centred on the interaction and similarities between light and atoms. He was notable for his wide-ranging expertise in relating theory to experiment, and was involved in all major efforts to understand non-classical light. A seminal paper (J Phys B 9, 1199 (1976)) by Walls with his first graduate student Howard Carmichael, showed how to create antibunched light, in which photons arrive at regular intervals, rather than randomly.
Walls was a pioneer in the study of ways that the particle-like nature of light (photons) could be controlled to make optical systems less susceptible to unwanted fluctuations, in particular by the use of squeezed light, a concept formulated by Carlton Caves. In squeezed light, some fluctuations can be made very small provided other fluctuations are correspondingly large.
He made major contributions to the theory of quantum measurement such as those involving Einstein's "which-path" experiment, and the quantum nondemolition measurement. Walls also used a simple field theoretical approach to explain and corroborate Dirac's description of photon interference and in particular Dirac's statement "that a photon interferes only with itself."
In the later stages of his career he focused his research efforts on the theoretical aspects of the newly created state of matter, the Bose–Einstein condensate (BECs). Some of his contributions in the field include the prediction of the interference signature of quantized vortices, and the collapses and revivals of the Josephson coupled BECs.
Walls was made a Fellow of the Royal Society of London, an honour bestowed on just 37 New Zealand-born scientists since the Society's establishment in 1660, and a Fellow of numerous academic societies such as the American Physical Society and the Royal Society of New Zealand. His many medals and prizes included the award in 1995 of the Paul Dirac Medal for theoretical physics.
He died of cancer in hospital in Auckland, aged 57.
- D. F. Walls, A simple field theoretical description of photon interference, Am. J. Phys. 45, 952-956 (1977).
- "Fascination with light". The Press. 20 May 1999. p. 7.