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Micro-fabricated ion traps for Quantum Information Processing; Highlights and lessons learned

Maunz, Peter L.; Blume-Kohout, Robin J.; Blain, Matthew G.; Benito, Francisco; Berry, Christopher; Clark, Craig R.; Clark, Susan M.; Colombo, Anthony P.; Dagel, Amber L.; Fortier, Kevin M.; Haltli, Raymond A.; Heller, Edwin J.; Lobser, Daniel L.; Mizrahi, Jonathan; Nielsen, Erik N.; Resnick, Paul J.; Rembetski, John F.; Rudinger, Kenneth M.; Scrymgeour, David S.; Sterk, Jonathan D.; Tabakov, Boyan; Tigges, Chris P.; Van Der Wall, Jay W.; Stick, Daniel L.

Abstract not provided.

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TYPE Conference Poster YEAR 2016
OSTI

Scattering mechanisms in shallow undoped Si/SiGe quantum wells

AIP Advances

Laroche, D.; Huang, S.H.; Nielsen, Erik N.; Chuang, Y.; Li, J.Y.; Liu, C.W.; Lu, Tzu-Ming L.

We report the magneto-transport study and scattering mechanism analysis of a series of increasingly shallow Si/SiGe quantum wells with depth ranging from ∼ 100 nm to ∼ 10 nm away from the heterostructure surface. The peak mobility increases with depth, suggesting that charge centers near the oxide/semiconductor interface are the dominant scattering source. The power-law exponent of the electron mobility versus density curve, μ nα, is extracted as a function of the depth of the Si quantum well. At intermediate densities, the power-law dependence is characterized by α ∼ 2.3. At the highest achievable densities in the quantum wells buried at intermediate depth, an exponent α ∼ 5 is observed. We propose and show by simulations that this increase in the mobility dependence on the density can be explained by a non-equilibrium model where trapped electrons smooth out the potential landscape seen by the two-dimensional electron gas.

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TYPE Journal Article YEAR 2015
DOIOSTIScopus

Transport through an impurity tunnel coupled to a Si/SiGe quantum dot

Applied Physics Letters

Foote, Ryan H.; Ward, Daniel R.; Prance, J.R.; Laros, James H.; Nielsen, Erik N.; Thorgrimsson, Brandur; Savage, D.E.; Friesen, Mark; Coppersmith, S.N.; Eriksson, M.A.

Achieving controllable coupling of dopants in silicon is crucial for operating donor-based qubit devices, but it is difficult because of the small size of donor-bound electron wavefunctions. Here, we report the characterization of a quantum dot coupled to a localized electronic state and present evidence of controllable coupling between the quantum dot and the localized state. A set of measurements of transport through the device enable the determination that the most likely location of the localized state is consistent with a location in the quantum well near the edge of the quantum dot. Our results are consistent with a gate-voltage controllable tunnel coupling, which is an important building block for hybrid donor and gate-defined quantum dot devices.

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TYPE Journal Article YEAR 2015
DOIOSTIScopusDOIOSTIScopus

Magneto-transport of an electron bilayer system in an undoped Si/SiGe double-quantum-well heterostructure

Applied Physics Letters

Laroche, D.; Huang, S.H.; Nielsen, Erik N.; Liu, C.W.; Li, J.Y.; Lu, Tzu-Ming L.

We report the design, the fabrication, and the magneto-transport study of an electron bilayer system embedded in an undoped Si/SiGe double-quantum-well heterostructure. Combined Hall densities (nHall) ranging from 2.6-×-1010-cm-2 to 2.7-×-1011-cm-2 were achieved, yielding a maximal combined Hall mobility (μHall) of 7.7-×-105-cm2/(V · s) at the highest density. Simultaneous electron population of both quantum wells is clearly observed through a Hall mobility drop as the Hall density is increased to nHall > 3.3-×-1010-cm-2, consistent with Schrödinger-Poisson simulations. The integer and fractional quantum Hall effects are observed in the device, and single-layer behavior is observed when both layers have comparable densities, either due to spontaneous interlayer coherence or to the symmetric-antisymmetric gap.

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TYPE Journal Article YEAR 2015
DOIOSTIScopus

Microwave-driven coherent operation of a semiconductor quantum dot charge qubit

Nature Nanotechnology

Laros, James H.; Kim, Dohun; Ward, D.R.; Simmons, C.B.; Blume-Kohout, Robin J.; Nielsen, Erik N.; Savage, D.E.; Lagally, M.G.; Friesen, Mark; Coppersmith, S.N.; Eriksson, M.A.

An intuitive realization of a qubit is an electron charge at two well-defined positions of a double quantum dot. This qubit is simple and has the potential for high-speed operation because of its strong coupling to electric fields. However, charge noise also couples strongly to this qubit, resulting in rapid dephasing at all but one special operating point called the 'sweet spot'. In previous studies d.c. voltage pulses have been used to manipulate semiconductor charge qubits but did not achieve high-fidelity control, because d.c. gating requires excursions away from the sweet spot. Here, by using resonant a.c. microwave driving we achieve fast (greater than gigahertz) and universal single qubit rotations of a semiconductor charge qubit. The Z-axis rotations of the qubit are well protected at the sweet spot, and we demonstrate the same protection for rotations about arbitrary axes in the X-Y plane of the qubit Bloch sphere. We characterize the qubit operation using two tomographic approaches: standard process tomography and gate set tomography. Both methods consistently yield process fidelities greater than 86% with respect to a universal set of unitary single-qubit operations.

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TYPE Journal Article YEAR 2015
DOIOSTIScopus
Results 76–100 of 168
Results 76–100 of 168