Thursday, January 27, 2011

Near-deterministic preparation of a single atom in an optical microtrap

*T. Grünzweig,*A. Hilliard,*M. McGovern*& M. F. Andersen

Neutral atoms stored in optical traps are strong candidates for a physical realization of a quantum logic device1, 2. Far off-resonance optical traps provide conservative potentials and excellent isolation from the environment, and they may be arranged to produce arbitrary arrays of traps, where each trap is occupied by a single atom that can be individually addressed3, 4, 5, 6. At present, significant effort is being expended on developing two-qubit gates based on coupling individual Rydberg atoms in adjacent optical microtraps7, 8, 9. A major challenge associated with this approach is the reliable generation of single-atom occupancy in each trap, as the loading efficiency in the past experiments has been limited to 50% (refs 4, 7, 8, 10, 11, 12). Here we report a loading efficiency of 82.7% in an optical microtrap. We achieve this by manipulating the collisions between pairs of trapped atoms through tailored optical fields and directly observing the resulting single atoms in the trap.

Monday, January 24, 2011

Optomechanically Induced Transparency

Stefan Weis, Rémi Rivière, Samuel Deléglise1, Emanuel Gavartin1, Olivier Arcizet3, Albert Schliesser and Tobias J. Kippenberg

Electromagnetically induced transparency is a quantum interference effect observed in atoms and molecules, in which the optical response of an atomic medium is controlled by an electromagnetic field. We demonstrated a form of induced transparency enabled by radiation-pressure coupling of an optical and a mechanical mode. A control optical beam tuned to a sideband transition of a micro-optomechanical system leads to destructive interference for the excitation of an intracavity probe field, inducing a tunable transparency window for the probe beam. Optomechanically induced transparency may be used for slowing and on-chip storage of light pulses via microfabricated optomechanical arrays.

Spin Hall Effect Transistor

Jörg Wunderlich, Byong-Guk Park, Andrew C. Irvine, Liviu P. Zârbo, Eva Rozkotová, Petr Nemec, Vít Novák, Jairo Sinova and Tomás Jungwirth

The field of semiconductor spintronics explores spin-related quantum relativistic phenomena in solid-state systems. Spin transistors and spin Hall effects have been two separate leading directions of research in this field. We have combined the two directions by realizing an all-semiconductor spin Hall effect transistor. The device uses diffusive transport and operates without electrical current in the active part of the transistor. We demonstrate a spin AND logic function in a semiconductor channel with two gates. Our study shows the utility of the spin Hall effect in a microelectronic device geometry, realizes the spin transistor with electrical detection directly along the gated semiconductor channel, and provides an experimental tool for exploring spin Hall and spin precession phenomena in an electrically tunable semiconductor layer.