Sandia National Laboratories

About: Sandia National Laboratories is a facility organization based out in Livermore, California, United States. It is known for research contribution in the topics: Laser & Thin film. The organization has 21501 authors who have published 46724 publications receiving 1484388 citations. The organization is also known as: SNL & Sandia National Labs.

Quantum control and process tomography of a semiconductor quantum dot hybrid qubit

Abstract: The similarities between gated quantum dots and the transistors in modern microelectronics--in fabrication methods, physical structure and voltage scales for manipulation--have led to great interest in the development of quantum bits (qubits) in semiconductor quantum dots. Although quantum dot spin qubits have demonstrated long coherence times, their manipulation is often slower than desired for important future applications, such as factoring. Furthermore, scalability and manufacturability are enhanced when qubits are as simple as possible. Previous work has increased the speed of spin qubit rotations by making use of integrated micromagnets, dynamic pumping of nuclear spins or the addition of a third quantum dot. Here we demonstrate a qubit that is a hybrid of spin and charge. It is simple, requiring neither nuclear-state preparation nor micromagnets. Unlike previous double-dot qubits, the hybrid qubit enables fast rotations about two axes of the Bloch sphere. We demonstrate full control on the Bloch sphere with π-rotation times of less than 100 picoseconds in two orthogonal directions, which is more than an order of magnitude faster than any other double-dot qubit. The speed arises from the qubit's charge-like characteristics, and its spin-like features result in resistance to decoherence over a wide range of gate voltages. We achieve full process tomography in our electrically controlled semiconductor quantum dot qubit, extracting high fidelities of 85 per cent for X rotations (transitions between qubit states) and 94 per cent for Z rotations (phase accumulation between qubit states).

AdDroid: privilege separation for applications and advertisers in Android

Abstract: Advertising is a critical part of the Android ecosystem---many applications use one or more advertising services as a source of revenue. To use these services, developers must bundle third-party, binary-only libraries into their applications. In this model, applications and their advertising libraries share permissions. Advertising-supported applications must request multiple privacy-sensitive permissions on behalf of their advertising libraries, and advertising libraries receive access to all of their host applications' other permissions. We conducted a study of the Android Market and found that 49% of Android applications contain at least one advertising library, and these libraries overprivilege 46% of advertising-supported applications. Further, we find that 56% of the applications with advertisements that request location (34% of all applications) do so only because of advertisements. Such pervasive overprivileging is a threat to user privacy. We introduce AdDroid, a privilege separated advertising framework for the Android platform. AdDroid introduces a new advertising API and corresponding advertising permissions for the Android platform. This enables AdDroid to separate privileged advertising functionality from host applications, allowing applications to show advertisements without requesting privacy-sensitive permissions.

Advances in selective wet oxidation of AlGaAs alloys

Abstract: We review the chemistry, microstructure, and processing of buried oxides converted from AlGaAs layers using wet oxidation Hydrogen is shown to have a central role in the oxidation reaction as the oxidizing agent and to reduce the intermediate predict As/sub 2/O/sub 3/ to As The stable oxide is amorphous (Al/sub x/Ga/sub 1-x/)/sub 2/O/sub 3/ which has no defects along the oxide/semiconductor interfaces but can exhibit strain at the oxide terminus due to volume shrinkage The influence of gas flow, gas composition, temperature, Al-content, and layer thickness on the oxidation rate are characterized to establish a reproducible process Linear oxidation rates with Arrhenius activation energies which strongly depend upon AlAs mole fraction are found The latter produces strong oxidation selectivity between AlGaAs layers with slightly differing Al-content Oxidation selectivity to thickness is also shown for layer thickness <60 nm Differences between the properties of buried oxides converted from AlGaAs and AlAs layers and the impact on selectively oxidized vertical cavity laser lifetime are reported

Ionomeric Poly(phenylene) Prepared by Diels−Alder Polymerization: Synthesis and Physical Properties of a Novel Polyelectrolyte

Abstract: A series of poly(phenylene)-based polyelectrolytes were synthesized from 1,4-bis(2,4,5-triphenylcyclopentadienone)benzene and 1,4-diethynylbenzene by Diels−Alder polymerization. Postsulfonation of this high molecular weight and thermochemically stable poly(phenylene) with chlorosulfonic acid resulted in homogeneous polyelectrolytes with controllable ion content (IEC = 0.98−2.2 mequiv/g). Fuel cell relevant properties such as high proton conductivity (123 mS/cm), chemical/thermal stability, and film toughness suggest that this polyelectrolyte material shows promise as a potential candidate for polymer electrolyte membrane fuel cells. Physical properties of this material, such as water uptake, thermal stability, and proton conductivity, are reported with respect to ion exchange capacity and compared to Nafion and a series of sulfonated poly(ether sulfone)s.