Electron spin decoherence in semiconductor quantum dots

Monday, October 30, 2006 (All day)
Dr. Xuedong Hu
Speaker's Institution: 
University at Buffalo, SUNY

Spins in semiconductor nanostructures are promising qubit candidates for a solid state quantum computer, and have seen some truly impressive experimental progresses in the past two years.  A central issue in spin-based quantum information processing is quantum coherence. In this talk I will discuss our

current theoretical understanding of electron spin decoherence in semiconductor quantum dots.  I will then focus on a recent theoretical study where we analyze electron spin decoherence through interaction with the surrounding nuclear spins. Specifically, we find that virtual nuclear spin flip-flops mediated by the electron contribute significantly to a complete decoherence of transverse electron spin correlation function on a time scale from tens of microseconds to a fraction of millisecond. Our results also show that a 90% nuclear polarization and an applied magnetic field can enhance the electron spin T_2 time by almost two orders of magnitude. In the long time limit, the electron spin correlation function has a non-exponential

1/t^2 decay in the presence of both polarized and unpolarized nuclei.