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Modeling the Transistor of the Future

Atom beams as a model DDT. LEFT: A beam of atoms crosses an area in which three laser beam overlap. The first beam places each atom in the same excited state. As the atoms pass through the region where the second and third lasers cross, their states may or may not be altered. If no atomic states are changed, the entire beam passes through the analyser -- the equivalent of maximum current in the drain of a working DDT. RIGHT: By “tuning” (changing the relative strengths of) the lasers, the state of the atoms in the beam changes in a predictable way, altering the proportion of atoms in each of the three possible ground states, two of which are dark. The quantum difference between the two dark states corresponds to the difference between spin-up and spin-down electrons in a DDT, with the laser beams acting as the gate.

Twenty years ago, Purdue University scientists proposed a highly promising design for a “spin effect” transistor – the Datta-Das transistor, or DDT. To date, however, no one has been able to build a working model. Now JQI researchers have devised a potential solution to the problem: creating a minutely controllable quantum model of the transistor action in a laboratory configuration -- in this case, an ultra-cold beam of atoms manipulated by a laser array. They developed a theoretical simulation in which the DDT electrons would be represented by a stream of ultracold atoms (neon and rubidium could work, among others) that pass through a space, corresponding to the gate in a DDT,  in which three crossed laser beams overlap. When the atoms are struck by the first laser beam, the beam puts all the atoms in the same quantum state -- equivalent to the identical spins of the source electrons in a DDT.

J.Y. Vaishnav, J. Ruseckas, C. W. Clark and G. Juzeliunas
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