May 2013
Abstracts of the QSIT Lunch Seminar, May 2, 2013
Harnessing nuclear spin polarization fluctuations in a semiconductor nanowire
Phani Peddibhotla, Department of Physics, University of Basel
Co-authors: F. Xue1, H. I. T. Hauge2, S. Assali2, E. P. A. M. Bakkers2,3, M. Poggio1
1 Department of Physics, University of Basel, 4056 Basel, Switzerland
2 Department of Applied Physics, Eindhoven University of Technology, The Netherlands
3 Kavli Institute of Nanoscience, Delft University of Technology, The Netherlands
Control over the dynamics of nanometer-scale nuclear spin systems is of interest both for fundamental studies and in applications such as quantum information processing and magnetic resonance imaging. Here we achieve such control through mechanical detection of nuclear spins in a semiconductor nanowire with a magnetic resonance force microscope (MRFM). Using radio frequency pulses, we demonstrate the real-time measurement and state preparation of small-scale nuclear spin ensembles. Our approach takes advantage of real-time feedback control to harness the statistical fluctuations of a nuclear spin ensemble [1, 2]. The technique is used to drive nuclear spin ensembles into non-equilibrium polarized and narrowed spin distributions. Furthermore, we are able to perform the long-term storage and readout of nuclear spin polarization.
References:
[1] R. Budakian, H. J. Mamin, B. W. Chui & D. Rugar. Creating order from random fluctuations in small spin ensembles. Science 307, 408-411 (2005).
[2] P. Peddibhotla, F. Xue, H. I. T. Hauge, S. Assali, E. P. A. M. Bakkers & M. Poggio. Harnessing nuclear spin polarization fluctuations in a semiconductor nanowire. Submitted.
Topological charge pumping of cold atoms
Lei Wang, Institute for Theoretical Physics, ETH Zurich
Topological charge pumping (TCP) is an important scheme for design and detection of topological phases in cold atoms. We propose an experiment setup to realize TCP in a 1D optical superlattice. The effect can be observed from quantized center-of-mass motion of the atomic cloud, which is a dynamical analog of the integer quantum Hall effect. Moreover, it suggests a general way to measure topological indices of 2D optical lattices. In particular, time-of-flight measurement along one spatial direction combined with in situ detection along the transverse direction allows direct read out the system's Chern number.