Mixed collective states of many spins

Mixed states of samples of spin s particles which are symmetric under permutations of the particles are described in terms of their total collective spin quantum numbers. We use this description to analyze the influence on spin squeezing due to imperfect initial state preparation.Comment: Section V on extension of the results to atoms with more than two levels has been rewritten. Accepted for publication in Phys. Rev.

Thermal spin injection and interface insensitivity in permalloy/aluminum metallic non-local spin valves

We present measurements of thermal and electrical spin injection in nanoscale metallic non-local spin valve (NLSV) structures. Informed by measurements of the Seebeck coefficient and thermal conductivity of representative films made using a micromachined Si-N thermal isolation platform, we use simple analytical and finite element thermal models to determine limits on the thermal gradient driving thermal spin injection and calculate the spin dependent Seebeck coefficient to be $-0.5\ \mu\mathrm{V}/\mathrm{K}< S_{s}<-1.3\ \mu\mathrm{V}/\mathrm{K}$. This is comparable in terms of the fraction of the absolute Seebeck coefficient to previous results, despite dramatically smaller electrical spin injection signals. Since the small electrical spin signals are likely caused by interfacial effects, we conclude that thermal spin injection is less sensitive to the FM/NM interface, and possibly benefits from a layer of oxidized ferromagnet, which further stimulates interest in thermal spin injection for applications in sensors and pure spin current sources

Designing Software Services for Business Agility

This presentation focuses on identifying the right services for a domain. The work is based on 10+ years of experience from StatoilHydro identifying and building services that are stable and useful for many years, even across technology shifts. By focusing on workflows with their activities, events and information usage, a set of reusable services can be identified through little effort (espescially if the workflows already exists) and built/composed from existing services. This approach is especially suitable for agile development practices, as it significantly reduces the amount of up-front analysis compared to traditional service design practices

Dynamics of the collective modes of an inhomogeneous spin ensemble in a cavity

We study the excitation dynamics of an inhomogeneously broadened spin ensemble coupled to a single cavity mode. The collective excitations of the spin ensemble can be described in terms of generalized spin waves and, in the absence of the cavity, the free evolution of the spin ensemble can be described as a drift in the wave number without dispersion. In this article we show that the dynamics in the presence of coupling to the cavity mode can be described solely by a modified time evolution of the wave numbers. In particular, we show that collective excitations with a well- defined wave number pass without dispersion from negative to positive valued wave numbers without populating the zero wave number spin wave mode. The results are relevant for multi-mode collective quantum memories where qubits are encoded in different spin waves.Comment: Published version. Some small changes and correction

Beitrag zur Lehre von der Amputation des Penis wegen Carcinom

Thesen: I.: Bei tiefer Amputation des Penis, ausgeführt an jugendlichen Männern, ist es ein Werk der Humanität die Kastration sofort anzuschliessen. II. Zum Zweck der Untersuchung bei Prostatahypertrophie soll man sich zuerst stets des elastischen Katheters bedienen. III. Bei Amputation des Penis sind stets die Inguinaldrüsen zu exstirpieren

Scalable designs for quantum computing with rare-earth-ion-doped crystals

Due to inhomogeneous broadening, the absorption lines of rare-earth-ion dopands in crystals are many order of magnitudes wider than the homogeneous linewidths. Several ways have been proposed to use ions with different inhomogeneous shifts as qubit registers, and to perform gate operations between such registers by means of the static dipole coupling between the ions. In this paper we show that in order to implement high-fidelity quantum gate operations by means of the static dipole interaction, we require the participating ions to be strongly coupled, and that the density of such strongly coupled registers in general scales poorly with register size. Although this is critical to previous proposals which rely on a high density of functional registers, we describe architectures and preparation strategies that will allow scalable quantum computers based on rare-earth-ion doped crystals.Comment: Submitted to Phys. Rev.