1,106 research outputs found
Consequences of wall stiffness for a beta-soft potential
Modifications of the infinite square well E(5) and X(5) descriptions of
transitional nuclear structure are considered. The eigenproblem for a potential
with linear sloped walls is solved. The consequences of the introduction of
sloped walls and of a quadratic transition operator are investigated.Comment: RevTeX 4, 8 pages, as published in Phys. Rev.
Optimal control of circuit quantum electrodynamics in one and two dimensions
Optimal control can be used to significantly improve multi-qubit gates in
quantum information processing hardware architectures based on superconducting
circuit quantum electrodynamics. We apply this approach not only to dispersive
gates of two qubits inside a cavity, but, more generally, to architectures
based on two-dimensional arrays of cavities and qubits. For high-fidelity gate
operations, simultaneous evolutions of controls and couplings in the two
coupling dimensions of cavity grids are shown to be significantly faster than
conventional sequential implementations. Even under experimentally realistic
conditions speedups by a factor of three can be gained. The methods immediately
scale to large grids and indirect gates between arbitrary pairs of qubits on
the grid. They are anticipated to be paradigmatic for 2D arrays and lattices of
controllable qubits.Comment: Published version
Innovation through Collaboration – The Orbis Cascade Alliance Shared Library Management Services Experience: An Interview with John F. Helme
Single-artificial-atom lasing using a voltage-biased superconducting charge qubit
We consider a system composed of a single artificial atom coupled to a cavity
mode. The artificial atom is biased such that the most dominant relaxation
process in the system takes the atom from its ground state to its excited
state, thus ensuring population inversion. A recent experimental manifestation
of this situation was achieved using a voltage-biased superconducting charge
qubit. Even under the condition of `inverted relaxation', lasing action can be
suppressed if the `relaxation' rate is larger than a certain threshold value.
Using simple transition-rate arguments and a semiclassical calculation, we
derive analytic expressions for the lasing suppression condition and the state
of the cavity in both the lasing and suppressed-lasing regimes. The results of
numerical calculations agree very well with the analytically derived results.
We start by analyzing a simplified two-level-atom model, and we then analyze a
three-level-atom model that should describe accurately the recently realized
superconducting artificial-atom laser.Comment: 21 pages in preprint format, 6 figure
Photodetection of propagating quantum microwaves in circuit QED
We develop the theory of a metamaterial composed of an array of discrete
quantum absorbers inside a one-dimensional waveguide that implements a
high-efficiency microwave photon detector. A basic design consists of a few
metastable superconducting nanocircuits spread inside and coupled to a
one-dimensional waveguide in a circuit QED setup. The arrival of a {\it
propagating} quantum microwave field induces an irreversible change in the
population of the internal levels of the absorbers, due to a selective
absorption of photon excitations. This design is studied using a formal but
simple quantum field theory, which allows us to evaluate the single-photon
absorption efficiency for one and many absorber setups. As an example, we
consider a particular design that combines a coplanar coaxial waveguide with
superconducting phase qubits, a natural but not exclusive playground for
experimental implementations. This work and a possible experimental realization
may stimulate the possible arrival of "all-optical" quantum information
processing with propagating quantum microwaves, where a microwave photodetector
could play a key role.Comment: 27 pages, submitted to Physica Scripta for Nobel Symposium on "Qubits
for Quantum Information", 200
Quantum information processing using quasiclassical electromagnetic interactions between qubits and electrical resonators
Electrical resonators are widely used in quantum information processing, by engineering an electromagnetic interaction with qubits based on real or virtual exchange of microwave photons. This interaction relies on strong coupling between the qubits' transition dipole moments and the vacuum fluctuations of the resonator in the same manner as cavity quantum electrodynamics (QED), and has consequently come to be called 'circuit QED' (cQED). Great strides in the control of quantum information have already been made experimentally using this idea. However, the central role played by photon exchange induced by quantum fluctuations in cQED does result in some characteristic limitations. In this paper, we discuss an alternative method for coupling qubits electromagnetically via a resonator, in which no photons are exchanged, and where the resonator need not have strong quantum fluctuations. Instead, the interaction can be viewed in terms of classical, effective 'forces' exerted by the qubits on the resonator, and the resulting resonator dynamics used to produce qubit entanglement are purely classical in nature. We show how this type of interaction is similar to that encountered in the manipulation of atomic ion qubits, and we exploit this analogy to construct two-qubit entangling operations that are largely insensitive to thermal or other noise in the resonator, and to its quality factor. These operations are also extensible to larger numbers of qubits, allowing interactions to be selectively generated among any desired subset of those coupled to a single resonator. Our proposal is potentially applicable to a variety of physical qubit modalities, including superconducting and semiconducting solid-state qubits, trapped molecular ions, and possibly even electron spins in solids.United States. Dept. of Defense. Assistant Secretary of Defense for Research & Engineering (United States. Air Force Contract FA8721-05-C-0002
Bonn Potential and Shell-Model Calculations for 206,205,204Pb
The structure of the nuclei 206,205,204Pb is studied interms of shell model
employing a realistic effective interaction derived from the Bonn A
nucleon-nucleon potential. The energy spectra, binding energies and
electromagnetic properties are calculated and compared with experiment. A very
good overall agreement is obtained. This evidences the reliability of our
realistic effective interaction and encourages use of modern realistic
potentials in shell-model calculations for heavy-mass nuclei.Comment: 4 pages, 4 figures, submitted to Physical Review
Two-dimensional cavity grid for scalable quantum computation with superconducting circuits
Superconducting circuits are among the leading contenders for quantum
information processing. This promising avenue has been strengthened with the
advent of circuit quantum electrodynamics, underlined by recent experiments
coupling on-chip microwave resonators to superconducting qubits. However,
moving towards more qubits will require suitable novel architectures. Here, we
propose a scalable setup for quantum computing where such resonators are
arranged in a two-dimensional grid with a qubit at each intersection. Its
versatility allows any two qubits on the grid to be coupled at a swapping
overhead independent of their distance and yields an optimal balance between
reducing qubit transition frequency spread and spurious cavity-induced
couplings. These features make this setup unique and distinct from existing
proposals in ion traps, optical lattices, or semiconductor spins. We
demonstrate that this approach encompasses the fundamental elements of a
scalable fault-tolerant quantum computing architecture.Comment: version as published in EPL 95 No 5 (March 2009) 50007, 5 page
Outcomes and outcome measures used in evaluation of communication training in oncology - a systematic literature review, an expert workshop, and recommendations for future research
BACKGROUND: Communication between health care provider and patients in oncology presents challenges. Communication skills training have been frequently developed to address those. Given the complexity of communication training, the choice of outcomes and outcome measures to assess its effectiveness is important. The aim of this paper is to 1) perform a systematic review on outcomes and outcome measures used in evaluations of communication training, 2) discuss specific challenges and 3) provide recommendations for the selection of outcomes in future studies.
METHODS: To identify studies and reviews reporting on the evaluation of communication training for health care professionals in oncology, we searched seven databases (Ovid MEDLINE, CENTRAL, CINAHL, EMBASE, PsychINFO, PsychARTICLES and Web of Science). We extracted outcomes assessed and the respective assessment methods. We held a two-day workshop with experts (n = 16) in communication theory, development and evaluation of generic or cancer-specific communication training and/or outcome measure development to identify and address challenges in the evaluation of communication training in oncology. After the workshop, participants contributed to the development of recommendations addressing those challenges.
RESULTS: Out of 2181 references, we included 96 publications (33 RCTs, 2 RCT protocols, 4 controlled trials, 36 uncontrolled studies, 21 reviews) in the review. Most frequently used outcomes were participants\u27 training evaluation, their communication confidence, observed communication skills and patients\u27 overall satisfaction and anxiety. Outcomes were assessed using questionnaires for participants (57.3%), patients (36.0%) and observations of real (34.7%) and simulated (30.7%) patient encounters. Outcomes and outcome measures varied widely across studies. Experts agreed that outcomes need to be precisely defined and linked with explicit learning objectives of the training. Furthermore, outcomes should be assessed as broadly as possible on different levels (health care professional, patient and interaction level).
CONCLUSIONS: Measuring the effects of training programmes aimed at improving health care professionals\u27 communication skills presents considerable challenges. Outcomes as well as outcome measures differ widely across studies. We recommended to link outcome assessment to specific learning objectives and to assess outcomes as broadly as possible
- …