Energy News  
Scientists Find Flaw In Quantum Dot Construction

This illustration shows a quantum dot (blue central bulge) bombarded from the top with laser light. The laser produces excitations (called excitons) inside the dot, and the electric fields generated by the top and bottom gold contacts pull the electrons (yellow) and holes (red) away. Other electrons/holes are undesirably produced instead on the wetting layer, causing interference. The semiconductor compounds used in these experiments are Gallium Arsenide (GaAs) and Indium Gallium Arsenide (InGaAs). See larger image. Image courtesy: Jose Villas-Boas, Ohio University.

Athens OH (SPX) Feb 14, 2005
Nanoscientists dream of developing a quantum computer, a device the size of a grain of sand that could be faster and more powerful than today's PCs. They've identified tiny artificial atoms � called "quantum dots" � as the most likely materials to build these machines, but have been puzzled by the dots' unpredictable behavior at the nanoscale.

Now a team of Ohio University physicists thinks it's found the problem � and has proposed a blueprint for building a better quantum dot.

The researchers, who published their findings in this week's issue of Physical Review Letters, argue that defects formed during creation of the quantum dots operate as a barrier to scientific experimentation.

Experimental scientists in Germany had blasted the quantum dots with light to create the quantum mechanical state needed to run a quantum computer.

But they couldn't consistently control that state, explained Sergio Ulloa, an Ohio University professor of physics and astronomy. Jose Villas-Boas, a postdoctoral fellow at Ohio University, Ulloa and Associate Professor Alexander Govorov developed theoretical models to learn what went wrong.

The problem, they argued, happens during the creation of the type of quantum dots under study. Using a molecular beam epitaxy chamber, scientists spray paint a surface with atoms under high temperatures, creating an atomic coating.

As more layers are added, the quantum dots bead up on the surface like droplets of water, Ulloa said. But a fine residue left behind on the surface that Ulloa calls the "wetting layer" can cause problems during experiments.

When experimental scientists blasted the quantum dots with a beam of light in previous studies, the wetting layer caused interference, instead of allowing the light to enter the dot and trigger the quantum state, he explained.

The study suggests that scientists could tweak the process by re-focusing the beam of light or changing the duration of the light pulses to negate the effects of the wetting layer, Villas-Boas said.

One experimental physicist already has used the theoretical finding to successfully manipulate a quantum dot in the lab, he added. "Now that they know the problem, they realize there are a few ways to avoid it," Villas-Boas said.

The new finding ultimately could lead to the creation of a better quantum dot and can help scientists understand more about quantum states, Ulloa added. "It's one more step towards the holy grail of finding a better quantum bit, which hopefully will lead to a quantum computer," he said.

Nanoscientists are creating quantum dots in many different ways, Ulloa noted, for use in various applications. The self-assembled type under study could be used in optical electronics and quantum computers. Other types, such as dots grown in a solution, might be used for solar energy applications.

The study also will help the Ohio University team better understand how to control the spin of electrons � a property that could be the underlying mechanism behind faster, more efficient future electronic devices, he added.

Community
Email This Article
Comment On This Article

Related Links
Ohio University
Ohio University's Nanoscale and Quantum Phenomena Institute
SpaceDaily
Search SpaceDaily
Subscribe To SpaceDaily Express
Understanding Time and Space



Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News


Unified Physics Theory Explains Animals Running Flying And Swimming
Durham NC (SPX) Jan 05, 2006
A single unifying physics theory can essentially describe how animals of every ilk, from flying insects to fish, get around, researchers at Duke University's Pratt School of Engineering and Pennsylvania State University have found. The team reports that all animals bear the same stamp of physics in their design.







  • Analysis: The Kremlin's Majority Share
  • Tiny Superconductors Withstand Stronger Magnetic Fields
  • UPI Energy Watch
  • UPI Energy Watch

  • Iran Says Ready To Sign Key Deal With Russian On Nuclear Plant
  • Tsunami Makes India's Nuke Workers Jittery
  • Japan Begins Controversial Uranium Test To Recycle Nuclear Fuel
  • Iran Makes Uranium Powder But Not Violating Nuclear Freeze - Diplomats





  • NASA Uses Remotely Piloted Airplane To Monitor Grapes



  • Political Fur Flies Over Marine One Deal
  • Military Sales Lift Lockheed Martin Profit To $372 Million
  • Asia Aviation To Defy Global Trend In 05
  • India Ruins Pakistan's F-16 Shopping Spree

  • NASA plans to send new robot to Jupiter
  • Los Alamos Hopes To Lead New Era Of Nuclear Space Tranportion With Jovian Mission
  • Boeing Selects Leader for Nuclear Space Systems Program
  • Boeing-Led Team to Study Nuclear-Powered Space Systems

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2006 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA PortalReports are copyright European Space Agency. All NASA sourced material is public domain. Additionalcopyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement