State-of-the-art microfabricated ion traps for quantum information research are approaching nearly one hundred control electrodes. We report here on the development and testing of a new architecture for microfabricated ion traps, built around ball-grid array (BGA) connections, that is suitable for increasingly complex trap designs. In the BGA trap, through-substrate vias bring electrical signals from the back side of the trap die to the surface trap structure on the top side. Gold-ball bump bonds connect the back side of the trap die to an interposer for signal routing from the carrier. Trench capacitors fabricated into the trap die replace area-intensive surface or edge capacitors. Wirebonds in the BGA architecture are moved to the interposer. These last two features allow the trap die to be reduced to only the area required to produce trapping fields. The smaller trap dimensions allow tight focusing of an addressing laser beam for fast single-qubit rotations. Performance of the BGA trap as characterized with ^40Ca^+ ions is comparable to previous surface-electrode traps in terms of ion heating rate, mode frequency stability, and storage lifetime. We demonstrate two-qubit entanglement operations with ^171Yb^+ ions in a second BGA trap.

: State-of-the art micro-fabricated ion traps for quantum information research have grown to incorporate upwards of a hundred control electrodes. In the typical architecture, a surface-electrode ion trap is fabricated on a thin chip that sits atop an industry standard CPGA carrier. To supply DC potentials for each electrode, pads on the CPGA are wirebonded to pads on the trap chip, while on-chip surface capacitors suppress pickup from the RF trapping fields. For large numbers of electrodes, the physical area taken up by these wirebonds and filter capacitors present significant constraints for ion trap design and operation. We report here on the development and successful testing of a new architecture for microfabricated ion traps, built around ball-grid array (BGA) connections and trench capacitors. In the BGA trap, through-substrate vias (TSVs) are used to bring electrical signals from the back side of the trap die to the top side. Gold-ball bump bonds connect the back side of the trap die to a separate interposer for signal routing from the CPGA carrier. Trench capacitors fabricated into the trap die eliminate the need for surface capacitors, reducing the trap die area by 30x.

High quality CdSe quantum-dot (QD) sensitized solar cells have been successfully fabricated by in-situ deposition of QDs into TiO2 nanoporous electron conductor (EC) films using a near room-temperature solution-based chemical bath deposition (CBD) method. An energy conversion efficiency of 4.44% under AM1.5G illumination is achieved on a device fabricated using CdSe QDs as a light absorber, TiO2 nanoparticles as an electron-conducting film, and a Polysulfide Na2S/S based electrolyte as a hole-conductor. Results also show that incident photo conversion efficiency (IPCE) of above 70% was obtained within a majority of the CdSe QD absorption spectrum range, and a peak value of 83% between 500-550nm. The light harvesting efficiency of the QD in the device is evaluated to between 75-85% in the same spectral range, indicating an internal quantum efficiency of greater than 95% was achieved. These results are among the best reported to date of the QD-based solar cells. We present data from prototype devices of various EC film thicknesses, morphologies, material composites, as well as QD deposition conditions and hole conductor variations and show how they impact key device metrics.