Lene Vestergaard Hau (Danish: [ˈle̝ːnə ˈvestɐˌkɒˀ ˈhɑw]; born November 13, 1959) is a Danish physicist and educator. She is the Mallinckrodt Professor of Physics and of Applied Physics at Harvard University. In 1999, she led a Harvard University team that, by use of a Bose–Einstein condensate, succeeded in slowing a beam of light to about 17 metres per second, and, in 2001, was able to stop a beam completely. Later work based on these experiments led to the transfer of light to matter, then from matter back into light, a process with important implications for quantum encryption and quantum computing. More recent work has focused on novel interactions between ultracold atoms and nanoscopic-scale systems. In addition to teaching physics and applied physics, she has taught Energy Science at Harvard, involving photovoltaic cells, nuclear power, batteries, and photosynthesis.
Early life, family and education Hau was born in Vejle, Denmark. She earned her bachelor's degree in mathematics in 1984 at the University of Aarhus in Denmark at the age of 24. Hau continued her studies there, receiving her master's degree in physics two years later. For her doctoral studies in quantum theory, Hau worked on ideas similar to those involved in fibre optic cables carrying light, but her work involved strings of atoms in a silicon crystal carrying electrons. While working towards her doctorate, Hau spent seven months at CERN, the European Laboratory for Particle Physics near Geneva. She received her doctorate from the University of Aarhus in 1991 at the age of 32, but by then her research interests had shifted.
Career In 1991, she joined the Rowland Institute for Science at Cambridge, Massachusetts as a scientific staff member, beginning to explore the possibilities of slow light and cold atoms. In 1999, at the age of 40, Hau accepted a two-year appointment as a postdoctoral fellow at Harvard University. Her formalized training is in theoretical physics, but her interest moved to experimental research in an effort to create a new form of matter known as a Bose–Einstein condensate. "Hau applied to the National Science Foundation for funds to make a batch of this condensate but was rejected on the grounds that she was a theorist for whom such experiments would be too difficult to do." Undeterred, she gained alternative funding and became one of the first handful of physicists to create such a condensate. In September 1999, she was appointed the Gordon Mckay Professor of Applied Physics and Professor of Physics at Harvard. She was also awarded tenure in 1999 and is now Mallinckrodt Professor of Physics and Applied Physics at Harvard. In 2001, she became the first person to stop light completely, using a Bose–Einstein condensate to achieve this. Since then, she has produced extensive research and new experimental work in electromagnetically induced transparency, various areas of quantum physics, photonics, and has contributed to the development of new quantum devices and novel nanoscale applications.
Qubit transfer Hau and her associates at Harvard University "have demonstrated exquisite control over light and matter in several experiments, but her experiment with 2 condensates is one of the most compelling". In 2006, they successfully transferred a qubit from light to a matter wave and back into light, again using Bose–Einstein condensates. Details of the experiment are discussed in the February 8, 2007, publication of the journal Nature. The experiment relies on the way that, according to quantum mechanics, atoms may behave as waves as well as particles. This enables atoms to do some counterintuitive things, such as passing through two openings at once. Within a Bose–Einstein condensate a light pulse is compressed by a factor of 50 million, without losing any of the information stored within it. In this Bose–Einstein condensate, information encoded in a light pulse can be transferred to the atom waves. Because all the atoms move coherently, the information does not dissolve into random noise. The light drives some of the cloud's roughly 1.8 million sodium atoms to enter into "quantum superposition" states, with a lower-energy component that stays put and a higher-energy component that travels between the two clouds. A second 'control' laser then writes the pulse shape into the atom's wave function. When this control beam is turned off, and the light pulse disappears, the 'matter copy' remains. Prior to this, researchers could not readily control optical information during its journey, except to amplify the signal to avoid fading. This experiment by Hau and her colleagues marked the first successful manipulation of coherent optical information. The new study is "a beautiful demonstration", says Irina Novikova, a physicist at the College of William and Mary in Williamsburg, VA. Before this result, she says, light storage was measured in milliseconds. "Here it's fractional seconds. It's a really dramatic time." Of its potential, Hau said, "While the matter is traveling between the two Bose–Einstein condensates, we can trap it, potentially for minutes, and reshape it – change it – in whatever way we want. This novel form of quantum control could also have applications in the developing fields of quantum information processing and quantum cryptography." Of the developmental implications, "This feat, the sharing around of quantum information in light-form and in not just one but two atom-forms, offers great encouragement to those who hope to develop quantum computers," said Jeremy Bloxham, dean of science in the Faculty of Arts and Sciences. Hau was awarded the George Ledlie Prize for this work, Harvard's Provost Steven Hyman noting "her work is path-breaking. Her research blurs the boundaries between basic and applied science, draws on the talent and people of two Schools and several departments, and provides a literally glowing example of how taking daring intellectual risks leads to profound rewards."
Cold atoms and nanoscale systems
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