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

Spin Coherence and 14^{14}N ESEEM Effects of Nitrogen-Vacancy Centers in Diamond with X-band Pulsed ESR

Pulsed ESR experiments are reported for ensembles of negatively-charged nitrogen-vacancy centers (NV$^-$) in diamonds at X-band magnetic fields (280-400 mT) and low temperatures (2-70 K). The NV$^-$ centers in synthetic type IIb diamonds (nitrogen impurity concentration $<1$~ppm) are prepared with bulk concentrations of $2\cdot 10^{13}$ cm$^{-3}$ to $4\cdot 10^{14}$ cm$^{-3}$ by high-energy electron irradiation and subsequent annealing. We find that a proper post-radiation anneal (1000$^\circ$C for 60 mins) is critically important to repair the radiation damage and to recover long electron spin coherence times for NV$^-$s. After the annealing, spin coherence times of T$_2 = 0.74$~ms at 5~K are achieved, being only limited by $^{13}$C nuclear spectral diffusion in natural abundance diamonds. At X-band magnetic fields, strong electron spin echo envelope modulation (ESEEM) is observed originating from the central $^{14}$N nucleus. The ESEEM spectral analysis allows for accurate determination of the $^{14}$N nuclear hypefine and quadrupole tensors. In addition, the ESEEM effects from two proximal $^{13}$C sites (second-nearest neighbor and fourth-nearest neighbor) are resolved and the respective $^{13}$C hyperfine coupling constants are extracted.Comment: 10 pages, 5 figure

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

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

Superconducting coplanar waveguide resonators for low temperature pulsed electron spin resonance spectroscopy

We discuss the design and implementation of thin film superconducting coplanar waveguide micro- resonators for pulsed ESR experiments. The performance of the resonators with P doped Si epilayer samples is compared to waveguide resonators under equivalent conditions. The high achievable filling factor even for small sized samples and the relatively high Q-factor result in a sensitivity that is superior to that of conventional waveguide resonators, in particular to spins close to the sample surface. The peak microwave power is on the order of a few microwatts, which is compatible with measurements at ultra low temperatures. We also discuss the effect of the nonuniform microwave magnetic field on the Hahn echo power dependence

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

Modulation of the high mobility two-dimensional electrons in Si/SiGe using atomic-layer-deposited gate dielectric

Metal-oxide-semiconductor field-effect transistors (MOSFET's) using atomic-layer-deposited (ALD) Al$_2$O$_3$ as the gate dielectric are fabricated on the Si/Si$_{1-x}$Ge$_x$ heterostructures. The low-temperature carrier density of a two-dimensional electron system (2DES) in the strained Si quantum well can be controllably tuned from 2.5$\times10^{11}$cm$^{-2}$ to 4.5$\times10^{11}$cm$^{-2}$, virtually without any gate leakage current. Magnetotransport data show the homogeneous depletion of 2DES under gate biases. The characteristic of vertical modulation using ALD dielectric is shown to be better than that using Schottky barrier or the SiO$_2$ dielectric formed by plasma-enhanced chemical-vapor-deposition(PECVD).Comment: 3 pages Revtex4, 4 figure

High speed sCMOS-based oblique plane microscopy applied to the study of calcium dynamics in cardiac myocytes

blique plane microscopy (OPM) is a form of light sheet microscopy that uses a single high numerical aperture microscope objective for both fluorescence excitation and collection. In this paper, measurements of the relative collection efficiency of OPM are presented. An OPM system incorporating two sCMOS cameras is then introduced that enables single isolated cardiac myocytes to be studied continuously for 22 seconds in two dimensions at 667 frames per second with 960 × 200 pixels and for 30 seconds with 960 × 200 × 20 voxels at 25 volumes per second. In both cases OPM is able to record in two spectral channels, enabling intracellular calcium to be studied via the probe Fluo-4 AM simultaneously with the sarcolemma and transverse tubule network via the membrane dye Cellmask Orange. The OPM system was then applied to determine the spatial origin of spontaneous calcium waves for the first time and to measure the cell transverse tubule structure at their point of origin. Further results are presented to demonstrate that the OPM system can also be used to study calcium spark parameters depending on their relationship to the transverse tubule structure