Ultrafast Laser Pulses Facilitate Storage and Retrieval of Quantum Phase Information in Cesium Rydberg States
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V2O5 Nanofibers Used in Fabricating Field-Effect Transistor
Ultrafast Laser Pulses Facilitate Storage and Retrieval of Quantum Phase Information in Cesium Rydberg States Using ultrafast lasers and a beam of cesium atoms, physicists at the University of Michigan have created a database that
stores and retrieves data in atomic quantum phases. As reported in the January 21 issue of Science, a computer randomly assigned data values to one quantum state of a single cesium atom. Using an ultrashort pulse of intense laser light, the scientists stored the information in the assigned quantum state by flipping the quantum phase or inverting the quantum wave for that state. Less than 1 ns later, the same atom was hit by a second laser pulse, which located the stored data by amplifying the flipped quantum state and suppressing all other states in the wave packet. The laser pulse used to store the data was produced by filtering a 100-fs laser pulse centered approximately on λ = 785 nm. The cesium atomic states interrogated were Rydberg p-states, with principal quantum numbers ranging from n = 29 to n = 38. Philip H. Bucksbaum, the Otto Laporte Professor of Physics at Michigan, said that L.K. Grover, in a 1997 paper published in Physics Review Letters, speculated that quantum 2-state data registers would be a faster, more efficient way to search and retrieve data than the classical binary system currently used because the rules of quantum mechanics allow a search in many locations simultaneously. “We test-
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G.T. Kim, J.G. Park, and Y.W. Park of Seoul National University, and J. Muster, V. Krstic, S. Roth, and M. Burghard of the Max-Planck Institute in Stuttgart have demonstrated that vanadium pentoxide (V2O5) nanofibers can be readily deposited in controllable densities on chemically modified Si/SiO2 substrates. The feasibility of using these nanofibers for electrical conduction in nanoscale devices is being investigated. Current attempts to use carbon nanotubes for this purpose suffer from the tendency of the nanotubes to form in dense networks, requiring potentially damaging ultrasonic treatment to separate the individual fibers. The deposi-
tion of V2O5 nanofibers requires no such separation step. As reported in the April 3 issue of Applied Physics Letters, nanofibers of V2O5 of molecular thickness are synthesized from ammonium(meta)vanadate and an acidic ion exchanger. To fabricate a field-effect transistor (FET), the nanofibers are deposited on a Si/SiO2 substrate, and 15-nm-thick Au/Pd electrodes are patterned on the surface 100 nm apart using electron-beam lithography. A 300-nm-thick layer of thermally grown SiO2 insulates the electrodes from a back gate consisting of the substrate doped with As + ions. The measured resistance of the V2O5 fibers connecting the electrodes ranged
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