Anisotropic Stark Effect and Electric-Field Noise Suppression for Phosphorus Donor Qubits in Silicon

We report the use of novel, capacitively terminated coplanar waveguide (CPW) resonators to measure the quadratic Stark shift of phosphorus donor qubits in Si. We confirm that valley repopulation leads to an anisotropic spin-orbit Stark shift depending on electric and magnetic field orientations relative to the Si crystal. By measuring the linear Stark effect, we estimate the effective electric field due to strain in our samples. We show that in the presence of this strain, electric-field sources of decoherence can be non-negligible. Using our measured values for the Stark shift, we predict magnetic fields for which the spin-orbit Stark effect cancels the hyperfine Stark effect, suppressing decoherence from electric-field noise. We discuss the limitations of these noise-suppression points due to random distributions of strain and propose a method for overcoming them

Simultaneous use of LANDSAT digital data with that of geophysical and geological surveys in geomathematical modelling for mineral exploration prediction

The author has identified the following significant results. A computer test file was created for the analysis of two rows in the pilot area. Data were organized into two groups with and without radioactivity above 1200 counts. The first 42 samples corresponded to the geographic cells which were anomalous, and the rest of the samples (70) were without anomalous values. Output analysis shows that all samples were properly classified

Electron Spin Resonance at the Level of 10000 Spins Using Low Impedance Superconducting Resonators

We report on electron spin resonance (ESR) measurements of phosphorus donors localized in a 200 square micron area below the inductive wire of a lumped element superconducting resonator. By combining quantum limited parametric amplification with a low impedance microwave resonator design we are able to detect around 20000 spins with a signal-to-noise ratio (SNR) of 1 in a single shot. The 150 Hz coupling strength between the resonator field and individual spins is significantly larger than the 1 - 10 Hz coupling rates obtained with typical coplanar waveguide resonator designs. Due to the larger coupling rate, we find that spin relaxation is dominated by radiative decay into the resonator and dependent upon the spin-resonator detuning, as predicted by Purcell

Reevaluation of the normative minerals of Sonora Pass rock standards - University of Nevada reports 7 and 12

Chemical analyses and normative minerals of Nevada mountain pass rock

Some anomalies in the E-layer of the ionosphere

If in the course of our investigation some problems have been clarified it is evident from the foregoing discussion that many characteristics of the E -layer remain mysterious, either having several equally plausible explanations or none at all; and there is no dearth of theoretical problems awaiting solution. Let us however summarize briefly the salient features of the present position.On the theoretical side we can now, with the aid of the formulae developed in Chapter 2, readily compute values of the maximum electron density Nᵐ throughout the day for any assigned variation of electron production q with solar zenith distance X, assuming a recombination law of electron loss. As a result, particularly with the extension of the calculation to the non -stationary conditions near sunrise and sunset, we may be certain that neither the anomalous variation of Δ fE nor the high exponent of cos X can be put down to inaccuracies of the theory. Hence we have been led to seek their origin elsewhere.Undoubtedly the main step forward in this respect has been the identification of the pre-noon perturbations in Nᵐ and in the height of the layer as effects of the vertical drift of neutral ionization associated with the Sq current system. This not only accounts for several previously unexplained anomalies, including increased values of fE near the equator, but is also perhaps of somewhat broader scientific interest; for it provides independent evidence of the existence and the location of these ionospheric currents previously only inferred from the data of the magnetic variations at the ground.This identification was first made on the basis of a statistical investigation of routine data; but the special measurements made at Slough have provided useful confirmation and have shown that the predicted dip in hᵐ does in fact occur. Our theoretical investigations of drift have also contributed by clarifying the nature of the drift effects and by enabling us to calculate the magnitudes of the drift velocity and of its gradient.As to the high exponent of cos X fit, the September results have suggested as a possible explanation that stratification of the layer in the morning and evening may lead to incorrect readings of fE. It seems that if at such times the upper discontinuity is taken to indicate fE instead of the lower one selected in normal practice, then the anomalous variation with cos X would disappear. A decision on this question must however await further evidence.Finally we have the low values of ΔfE at low cos X( leading to an apparent rapid increase of recombination coefficient with height; but so far no satisfactory explanation of this anomaly has been forthcoming, and there is only the somewhat nebulous suggestion that it may be related to the curious "ledging" phenomena which develop in the afternoon period.Ledging may also be responsible for other unexplained features such as the unexpected pre-noon dip in yᵐ, and the anomalo!is variation of h'E in the September data. Indeed it is hardly possible to study a large number of E-region records without becoming convinced that stratification, including all the phenomena variously described as "Eˢ ", is a major problem for future investigation. It may be that, following clarification of the Sq effects, little progress will be made in understanding other peculiarities of the region until the problem of these various subsidiary layers, or "ledges", has been solved

Addressing spin transitions on 209Bi donors in silicon using circularly-polarized microwaves

Over the past decade donor spin qubits in isotopically enriched $^{28}$Si have been intensely studied due to their exceptionally long coherence times. More recently bismuth donor electron spins have become popular because Bi has a large nuclear spin which gives rise to clock transitions (first-order insensitive to magnetic field noise). At every clock transition there are two nearly degenerate transitions between four distinct states which can be used as a pair of qubits. Here it is experimentally demonstrated that these transitions are excited by microwaves of opposite helicity such that they can be selectively driven by varying microwave polarization. This work uses a combination of a superconducting coplanar waveguide (CPW) microresonator and a dielectric resonator to flexibly generate arbitrary elliptical polarizations while retaining the high sensitivity of the CPW

Developments in electromagnetic tomography instrumentation.

A new EMT sensor and instrumentation is described which combines the best features of previous systems and has a modular structure to allow for future system expansion and development

Geological and geothermal investigations for HCMM-derived data

An attempt was made to match HCMM- and U2HCMR-derived temperature data over two test sites of very local size to similar data collected in the field at nearly the same times. Results indicate that HCMM investigations using resolutions cells of 500 m or so are best conducted with areally-extensive sites, rather than point observations. The excellent quality day-VIS imagery is particularly useful for lineament studies, as is the DELTA-T imagery. Attempts to register the ground observed temperatures (even for 0.5 sq mile targets) were unsuccessful due to excessive pixel-to-pixel noise on the HCMM data. Several computer models were explored and related to thermal parameter value changes with observed data. Unless quite complex models, with many parameters which can be observed (perhaps not even measured (perhaps not even measured) only under remote sensing conditions (e.g., roughness, wind shear, etc) are used, the model outputs do not match the observed data. Empirical relationship may be most readily studied

Computer program to predict noise of general aviation aircraft: User's guide

Program NOISE predicts General Aviation Aircraft far-field noise levels at FAA FAR Part 36 certification conditions. It will also predict near-field and cabin noise levels for turboprop aircraft and static engine component far-field noise levels

Coherence of Spin Qubits in Silicon

Given the effectiveness of semiconductor devices for classical computation one is naturally led to consider semiconductor systems for solid state quantum information processing. Semiconductors are particularly suitable where local control of electric fields and charge transport are required. Conventional semiconductor electronics is built upon these capabilities and has demonstrated scaling to large complicated arrays of interconnected devices. However, the requirements for a quantum computer are very different from those for classical computation, and it is not immediately obvious how best to build one in a semiconductor. One possible approach is to use spins as qubits: of nuclei, of electrons, or both in combination. Long qubit coherence times are a prerequisite for quantum computing, and in this paper we will discuss measurements of spin coherence in silicon. The results are encouraging - both electrons bound to donors and the donor nuclei exhibit low decoherence under the right circumstances. Doped silicon thus appears to pass the first test on the road to a quantum computer.Comment: Submitted to J Cond Matter on Nov 15th, 200