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           COLLOQUIUM OF THE COMPUTATIONAL MATERIALS SCIENCE CENTER
                              College of Science
                       (CDS Department CSI 898-Sec 001)
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    Coherent Control of a Single Electron Spin in a Quantum Dot: 
         Is Nuclear Spin Polarization Friend or Foe?

                        Andrew Shabaev
      Dep. of Physics and Astronomy, George Mason University

Semiconductor quantum dots are nanometer scale structures with a discrete 
energy spectrum that results from the confinement of carriers (electrons 
and holes) within the dots. Modern technological advances open an 
opportunity to control the size, shape and composition of quantum dots. 
A quantum dot can be charged with a single excess electron. The use of 
not only the charge, but also the spin degree of freedom opens broad
opportunities for development of spin-based electronics, or spintronics. 
The spin of the confined electron can be used for information technology 
including quantum information processing. In particular, a single electron 
localized in a quantum dot represents a promising qubit for a scalable 
spin-based quantum computer. The ability to maintain and control spin 
coherence for a substantially long period of time is extremely important
for applications in hardware for information technology.  The hyperfine 
interaction of an electron with more than 100,000 nuclei of a quantum dot 
is unavoidable. Randomly fluctuating nuclear spins are considered the main
source of decoherence of a single spin and dephasing of spins in an array 
of quantum dots. Recently, however, we demonstrated that the same nuclei 
can act constructively if one can manage to use the hyperfine coupling with
the resident electron to control the nuclear spins. The harnessed nuclear 
spins, in their turn, help control the electron spin coherence and store 
the information about the electron spin for a strikingly long period of time.
  
                        Monday , November 5, 2007
                                  4:30 pm
                     Room 301, Research I, Fairfax Campus

Refreshments will be served at 4:15 PM.
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Find the schedule at www.cmasc.gmu.edu/seminar/schedule.html
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