Publications

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We present a scalable phonon-based quantum computer on a phononic crystal platform. Practical schemes involve selective placement of a single acceptor atom in the peak of the strain field in a high-Q phononic crystal cavity that enables coupling of the phonon modes to the energy levels of the atom. We show theoretical optimization of the cavity design and coupling waveguide, along with estimated performance figures of the coupled system. A qubit can be created by entangling a phonon at the resonance frequency of the cavity with the atom states. Qubits based on this half-sound, half-matter quasi-particle, called a phoniton, may outcompete other quantum architectures in terms of combined emission rate, coherence lifetime, and fabrication demands.

The systematic design, fabrication, and characterization of an isolated, single-mode, 90° bend phononic crystal (PnC) waveguide are presented. A PnC consisting of a 2D square array of circular air holes in an aluminum substrate is used, and waveguides are created by introducing a line defect in the PnC lattice. A high transmission coefficient is observed (-1 dB) for the straight sections of the waveguide, and an overall 2.3 dB transmission loss is observed (a transmission coefficient of 76%) for the 90° bend. Further optimization of the structure may yield higher transmission efficiencies. This manuscript shows the complete design process for an engineered 90° bend PnC waveguide from inception to experimental demonstration.

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The Frequency Translation to Demonstrate a Hybrid Quantum Architecture project focused on developing nonlinear optics to couple two different ion species and make their emitted UV photons indistinguishable. Successful demonstration of photonic coupling of different ion species lays the foundation for coupling drastically different types of qubits, such as ions and quantum dots. Frequency conversion of single photons emitted from single ions remains a "hot" topic with many groups pursing this effort; however due to challenges in producing short period periodically poled crystal it has yet to be realized. This report details the efforts of trying to frequency convert single photons emitted from trapped ions to other wavelengths. We present our theoretical studies of candidate platforms for frequency conversion: photonic crystal fibers, X⁽²⁾ nonlinear crystals in optical cavities, and photonic crystal cavities. We also present experiment results in ion trapping X⁽²⁾ nonlinear crystals measurements and photonic crystal fabrication

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The thermal conductivity of single crystal silicon was engineered using lithographically formed phononic crystals. Specifically, sub-micron periodic through-holes were patterned in 500nm-thick silicon membranes to construct phononic crystals, and through phonon scattering enhancement, heat transfer was significantly reduced. The thermal conductivity of silicon phononic crystals was measured as low as 32.6W/mK, which is a ∼75% reduction compared to bulk silicon thermal conductivity [1]. This corresponds to a 37% reduction even after taking into account the contributions of the thin-film and volume reduction effects, while the electrical conductivity was reduced only by as much as the volume reduction effect. The demonstrated method uses conventional lithography-based technologies that are directly applicable to diverse micro/nano-scale devices, leading toward huge performance improvements where heat management is important. © 2011 IEEE.

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