Researchers peer into quantum dots
By Eric Smalley, Technology Research NewsResearchers at the University of Nottingham in England have developed an imaging technique that lets them see electronic activity inside quantum dots.
Magnetotunneling spectroscopy uses magnetic fields to make two-dimensional maps of the wave function of electrons trapped inside quantum dots. Electrons, like other subatomic particles, behave like both particles and waves, and the electron wave function is the shape of the electron's wave.
The imaging technique should help efforts to control the growth of quantum dots, which are 10- to 20-nanometer specks of semiconductor material, and apply them to technologies ranging from lasers to quantum computers.
"Applying our technique, it would be possible to see how the electron wave function could be fine-tuned by changing the semiconductor growth conditions, which in turn change the precise shape, size and composition of the dots," said Laurence Eaves, a physics professor at the University of Nottingham.
Measuring the electron wave function in quantum dots would allow researchers to determine how efficient particular quantum dots would be in light emitting devices like lasers, said J. K. Furdyna, a Notre Dame University physics professor.
"Everything about the electronic properties of quantum dots... is disguised in this wave function," Furdyna said. "If you... understand the wave function, you can maybe make better predictions about other applications of quantum dots."
Furdyna's colleagues at Notre Dame, for instance, are attempting to use arrays of quantum dots to make high-speed, low-power computers. (See "Quantum dot computing advances")
The problems of making connections between quantum dots and keeping the electrons in the right places make quantum dot computing very difficult, said Eaves. "The precise shape and form of the wave function is extremely important for understanding and optimizing the performance of such proposed structures," he said.
Magnetotunneling spectroscopy could also help determine whether quantum dot computing is ultimately even possible, said Gregory L. Snider, associate professor of electrical engineering at Notre Dame and a researcher working on the Quantum-dot Cellular Automata project.
"One of the questions that nobody's been able to answer is can you put [quantum dots] close enough together that electrons can tunnel between them in a way that would be useful," Snider said.
Eaves' colleagues were E. E. Vdovin, Alexander Levin, Amalia Patane, Peter C. Main, Yurii V. Dubrovskii and Mohamed Henini of the University of Nottingham, Y. N. Khanin of the Russian Academy of Sciences, and Geoff Hill of the University of Sheffield. The researchers publish their work in the October 6, 2000 issue of the journal Science.
The research was funded by the Engineering & Physical Sciences Research Council and the Royal Society in England and the Fundacão de Amparo à Pesquisa do Estado de São Paulo in Brazil.
Timeline: Now
Funding: Government, Private
TRN Categories: Nanotechnology; Quantum Computing
Story Type: News
Related Elements: Images, Technical paper "Imaging the Electron Wave Function in Self-Assembled Quantum Dots" in Science Oct. 6, 2000
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October 11, 2000
Page One
Quantum dot logic advances
Researchers peer into quantum dots
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