APS March Meeting 2012
Volume 57, Number 1
Monday–Friday, February 27–March 2 2012;
Boston, Massachusetts
Session X29: Focus Session: Semiconductor Qubits - Managing or Eliminating Nuclei
2:30 PM–5:30 PM,
Thursday, March 1, 2012
Room: 259A
Sponsoring
Unit:
GQI
Chair: Thaddeus Ladd, HRL
Abstract ID: BAPS.2012.MAR.X29.1
Abstract: X29.00001 : Ultrafast optical coherent control of individual electron and hole spins in a semiconductor quantum dot
2:30 PM–3:06 PM
Preview Abstract
Abstract
Author:
Kristiaan De Greve
(E.L. Ginzton Laboratory, Stanford University)
We report on the complete optical coherent control of individual electron
and hole spin qubits in InAs quantum dots. With a magnetic field in Voigt
geometry, broadband, detuned optical pulses couple the spin-split ground
states, resulting in Rabi flopping. In combination with the Larmor
precession around the external magnetic field, this allows an arbitrary
single-qubit operation to be realized in less than 20 picoseconds [1,2].
Slow fluctuations in the spin's environment lead to shot-to-shot variations
in the Larmor precession frequency. In a time-ensemble measurement, these
would prevent a measurement of the true decoherence of the qubit, and
instead give rise to ensemble dephasing. This effect was overcome by
implementing a spin echo measurement scheme for both electron and hole
spins, where an optical $\pi $-pulse refocuses the spin coherence and
filters out the slow variations in Larmor precession frequency. We measured
coherence times up to 3 microseconds [2,3].
Finally, our optical pulse manipulation scheme allows us to probe the
hyperfine interaction between the single spin and the nuclei in the quantum
dot. Interesting non-Markovian dynamics could be observed in the
free-induction decay of a single electron spin, whereas the complete absence
of such effects illustrates the reduction of the hyperfine interaction for
hole spin qubits. We measured and modeled these effects, and explain the
non-Markovian electron spin dynamics as involving a feedback effect
resulting from both the strong Overhauser shift of the electron spin and
spin dependent nuclear relaxation [2,4].
\\[4pt]
[1] D. Press, T. D. Ladd, B. Zhang and Y. Yamamoto, Nature \textbf{456}, 218 (2008)\\[0pt]
[2] K. De Greve, P. McMahon, D. Press \textit{et al.}, Nat. Phys. \textbf{7}, 872 (2011)\\[0pt]
[3] D. Press, K. De Greve, P. McMahon \textit{et al.}, Nat. Phot. \textbf{4}, 367 (2010)\\[0pt]
[4] T. D. Ladd, D. Press, K. De Greve \textit{et al.}, Phys. Rev. Lett. 105, 107401 (2010)
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.MAR.X29.1