627 research outputs found
High fidelity readout scheme for rare-earth solid state quantum computing
We propose and analyze a high fidelity readout scheme for a single instance
approach to quantum computing in rare-earth-ion-doped crystals. The scheme is
based on using different species of qubit and readout ions, and it is shown
that by allowing the closest qubit ion to act as a readout buffer, the readout
error can be reduced by more than an order of magnitude. The scheme is shown to
be robust against certain experimental variations, such as varying detection
efficiencies, and we use the scheme to predict the expected quantum fidelity of
a CNOT gate in these solid state systems. In addition, we discuss the potential
scalability of the protocol to larger qubit systems. The results are based on
parameters which we believed are experimentally feasible with current
technology, and which can be simultaneously realized.Comment: 7 pages, 5 figure
Noise characteristics of single shot broadband Raman-resonant CARS with single- and multimode lasers
A simple model is presented as an aid in understanding, first, the relative noise performance and, second, the noise reduction achievable by referencing, in different experimental approaches to single shot broadband coherent anti-Stokes Raman scattering (CARS). Qualitative agreement is obtained with previous experimental investigations of CARS noise. The broadband dye laser radiation is described as the sum of independent modes with random phases. The dye laser contribution to the CARS noise is then approximately inversely proportional to the square root of the number of dye laser modes generating the detected signal. A fundamental idea is that in Raman resonant spectra only the number of Stokes modes actually participating in driving the Raman resonance should be counted. This means, e.g., that for narrow Raman resonances, as in an atmospheric flame, the noise generated by the dye laser will be higher for a single-mode pump laser than for a multimode pump laser with the experimental CARS configuration normally employed. The implications of the model for the dual broadband type CARS techniques are also discussed
Background reduction and sensitivity for germanium double beta decay experiments
Germanium detectors have very good capabilities for the investigation of rare
phenomena like the neutrinoless double beta decay. Rejection of the background
entangling the expected signal is one primary goal in this kind of experiments.
Here, the attainable background reduction in the energy region where the
neutrinoless double beta decay signal of 76Ge is expected to appear has been
evaluated for experiments using germanium detectors, taking into consideration
different strategies like the granularity of the detector system, the
segmentation of each individual germanium detector and the application of Pulse
Shape Analysis techniques to discriminate signal from background events.
Detection efficiency to the signal is affected by background rejection
techniques, and therefore it has been estimated for each of the background
rejection scenarios considered. Finally, conditions regarding crystal mass,
radiopurity, exposure to cosmic rays, shielding and rejection capabilities are
discussed with the aim to achieve a background level of 10-3 c keV-1 kg-1 y-1
in the region of interest, which would allow to explore neutrino effective
masses around 40 meV.Comment: 13 pages, 19 figures. Accepted by Astroparticle Physic
Quantum memory for non-stationary light fields based on controlled reversible inhomogeneous broadening
We propose a new method for efficient storage and recall of non-stationary
light fields, e.g. single photon time-bin qubits, in optically dense atomic
ensembles. Our approach to quantum memory is based on controlled, reversible,
inhomogeneous broadening. We briefly discuss experimental realizations of our
proposal.Comment: 4 page
Coherent control of collective spontaneous emission in an extended atomic ensemble and quantum storage
Coherent control of collective spontaneous emission in an extended atomic
ensemble resonantly interacting with single-photon wave packets is analyzed. A
scheme for coherent manipulation of collective atomic states is developed such
that superradiant states of the atomic system can be converted into subradiant
ones and vice versa. Possible applications of such a scheme for optical quantum
state storage and single-photon wave packet shaping are discussed. It is shown
that also in the absence of inhomogeneous broadening of the resonant line,
single-photon wave packets with arbitrary pulse shape may be recorded as a
subradiant state and reconstructed even although the duration of the wave
packets is larger than the superradiant life-time. Specifically the
applicability for storing time-bin qubits, which are used in quantum
cryptography is analyzed.Comment: 11 pages, 4 figures, submitted to PR
Helping a crocodile to learn German plurals: Children’s online judgment of actual, potential and illegal plural forms
A substantial tradition of linguistic inquiry has framed the knowledge of native speakers in terms of their ability to determine the grammatical acceptability of language forms that they encounter for the first time. In the domain of morphology, the productivity framework of Dressler (CLASNET Working papers 7, 1997) has emphasized the importance of this ability in terms of the graded potentiality of non-existing multimorphemic forms. The goal of this study was to investigate what role the notion of potentiality plays in online lexical well-formedness judgment among children who are native speakers of Austrian German. A total of 114 children between the ages of six and ten and a total of 40 adults between the ages of 18 and 30 (as a comparison group) participated in an online well-formedness judgment task which focused on pluralized German nouns. Concrete, picturable, high frequency German nouns were presented in three pluralized forms: (a) actual existing plural form, (b) morphologically illegal plural form, (c) potential (but not existing) plural form. Participants were shown pictures of the nouns (as a set of three identical items) and simultaneously heard one of three pluralized forms for each noun. Response latency and judgment type served as dependent variables. Results indicate that both children and adults are sensitive to the distinction between illegal and potential forms (neither of which they would have encountered). For all participants, plural frequency (rather than frequency of the singular form) affected responses for both existing and non-existing words. Other factors increasing acceptability were the presence of supplementary umlaut in addition to suffixation and homophony with existing words or word forms
Quantum Memories. A Review based on the European Integrated Project "Qubit Applications (QAP)"
We perform a review of various approaches to the implementation of quantum
memories, with an emphasis on activities within the quantum memory sub-project
of the EU Integrated Project "Qubit Applications". We begin with a brief
overview over different applications for quantum memories and different types
of quantum memories. We discuss the most important criteria for assessing
quantum memory performance and the most important physical requirements. Then
we review the different approaches represented in "Qubit Applications" in some
detail. They include solid-state atomic ensembles, NV centers, quantum dots,
single atoms, atomic gases and optical phonons in diamond. We compare the
different approaches using the discussed criteria.Comment: 22 pages, 12 figure
Magnetic moments of Coulomb excited states for radioactive beams of Te and Xe isotopes at REX-ISOLDE
Does Greater Low Frequency EEG Activity in Normal Immaturity and in Children with Epilepsy Arise in the Same Neuronal Network?
Greater low frequency power (<8Hz) in the electroencephalogram (EEG) at rest is normal in the immature developing brain of children when compared to adults. Children with epilepsy also have greater low frequency interictal resting EEG activity. Whether these power elevations reflect brain immaturity due to a developmental lag or the underlying epileptic pathophysiology is unclear. The present study addresses this question by analyzing spectral EEG topographies and sources for normally developing children and children with epilepsy. We first compared the resting EEG of healthy children to that of healthy adults to isolate effects related to normal brain immaturity. Next, we compared the EEG from 10 children with generalized cryptogenic epilepsy to the EEG of 24 healthy children to isolate effects related to epilepsy. Spectral analysis revealed that global low (delta: 1-3Hz, theta: 4-7Hz), medium (alpha: 8-12Hz) and high (beta: 13-25Hz) frequency EEG activity was greater in children without epilepsy compared to adults, and even further elevated for children with epilepsy. Topographical and tomographic EEG analyses showed that normal immaturity corresponded to greater delta and theta activity at fronto-central scalp and brain regions, respectively. In contrast, the epilepsy-related activity elevations were predominantly in the alpha band at parieto-occipital electrodes and brain regions, respectively. We conclude that lower frequency activity can be a sign of normal brain immaturity or brain pathology depending on the specific topography and frequency of the oscillating neuronal networ
Study of bound states in 12Be through low-energy 11Be(d,p)-transfer reactions
The bound states of 12Be have been studied through a 11Be(d,p)12Be transfer
reaction experiment in inverse kinematics. A 2.8 MeV/u beam of 11Be was
produced using the REX-ISOLDE facility at CERN. The outgoing protons were
detected with the T-REX silicon detector array. The MINIBALL germanium array
was used to detect gamma rays from the excited states in 12Be. The gamma-ray
detection enabled a clear identification of the four known bound states in
12Be, and each of the states has been studied individually. Differential cross
sections over a large angular range have been extracted. Spectroscopic factors
for each of the states have been determined from DWBA calculations and have
been compared to previous experimental and theoretical results
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