| 1. |
- Jiang, Wentao, et al.
(författare)
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Optically heralded microwave photon addition
- 2023
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Ingår i: Nature Physics. - 1745-2481 .- 1745-2473. ; 19:10, s. 1423-1428
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Tidskriftsartikel (refereegranskat)abstract
- Photons with optical frequencies of a few hundred terahertz are perhaps the only way to distribute quantum information over long distances. Superconducting qubits, which are one of the most promising approaches for realizing large-scale quantum machines, operate on microwave photons at frequencies that are ~40,000 times lower. To network these quantum machines across appreciable distances, we must bridge this frequency gap. Here we implement and demonstrate a transducer that can generate correlated optical and microwave photons. We use it to show that by detecting an optical photon we generate an added microwave photon with an efficiency of ~35%. Our device uses a gigahertz nanomechanical resonance as an intermediary, which efficiently couples to optical and microwave channels through strong optomechanical and piezoelectric interactions. We show continuous operation of the transducer with 5% frequency conversion efficiency, input-referred added noise of ~100, and pulsed microwave photon generation at a heralding rate of 15 Hz. Optical absorption in the device generates thermal noise of less than two microwave photons. Improvements of the system efficiencies and device performance are necessary to realize a high rate of entanglement generation between distant microwave-frequency quantum nodes, but these enhancements are within reach.
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| 2. |
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| 3. |
- Heaney, Alice, et al.
(författare)
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Evaluation of the Unidimensional Fatigue Impact Scale in Crohn’s Disease : the importance of local item dependency
- 2022
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Ingår i: Journal of Nursing Measurement. - : Springer Publishing Company. - 1061-3749 .- 1945-7049. ; 30:2, s. 345-360
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: The Unidimensional Fatigue Impact Scale (U-FIS) was developed for use in a multiple sclerosis population. The aim was to determine whether the U-FIS is a valid tool for measuring the impact of fatigue in Crohn's disease (CD). METHOD: CD patients completed the U-FIS as part of a validation study of the Crohn's Life Impact Questionnaire (CLIQ). Data were analyzed according to Rasch measurement theory (RMT). RESULTS: Two hundred sixty-one completed U-FIS questionnaires were available for analysis. After rescoring the items to resolve disordered thresholds, all 22 items showed acceptable RMT fit. However, there was considerable local item dependency (LID). CONCLUSION: The U-FIS did not provide unidimensional measurement in a sample of CD patients due to high levels of LID. Combining the three FIS outcomes into a single measure was not justified.
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| 4. |
- de Beeck, Camiel Op, et al.
(författare)
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III/V-on-lithium niobate amplifiers and lasers
- 2021
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Ingår i: Optica. - 2334-2536. ; 8:10, s. 1288-1289
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We demonstrate electrically pumped, heterogeneously integrated lasers on thin-film lithium niobate, featuring electro-optic wavelength tunability. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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| 5. |
- McKenna, Stephen P, et al.
(författare)
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International development of the Alzheimer's patient partners life impact questionnaire (APPLIQue)
- 2020
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Ingår i: American Journal of Alzheimer’s Disease and Other Dementia. - : SAGE Publications. - 1533-3175 .- 1938-2731. ; 35, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- AIM: Informal caregivers play a vital role in the care of people with Alzheimer's Disease (AD), yet caregiving is associated with caregivers' burden. The initial objective of the study was to develop a new outcome measure to assess quality of life (QoL) in AD caregivers. METHODS: Informal (non-professional) caregivers providing 75% or more of the care activities for, and living in the same household as, a person with AD were invited to take part in the study. Qualitative interviews (N = 40) were conducted with AD caregivers in the UK and thematic analyses were applied to generate a pool of potential items. A draft questionnaire was produced and adapted for use in Italy, Spain, Germany and the US. In each of the 5 countries, cognitive debriefing interviews (N = 76) were conducted to determine the questionnaire's face and content validity, followed by a postal validation survey (N = 268). The data from these surveys were combined to reduce the number of items and assess the new questionnaire's psychometric properties. RESULTS: Thematic analysis of the UK interview transcripts generated a draft questionnaire, which was successfully translated into each additional language. The items were well accepted and easy to complete. However, reanalysis of the qualitative interview data revealed that spousal and non-spousal caregivers identified different experiences of caregiving. A review of the item pool indicated that items were primarily targeted at spousal caregivers. Therefore, further analyses of the postal survey data included spousal caregivers only (n = 116). The results supported scaling assumptions (e.g., corrected item-total correlations ≥0.32), targeting (e.g., floor/ceiling effects <2.5%), internal consistency (α ≥0.93) and test-retest reliability (rs = 0.88) of the new questionnaire, according to classical test theory. Assessment of external construct validity yielded results in accordance with a priori expectations. QoL scores were most strongly related to scores on the emotional reactions sections of the Nottingham Health Profile and the General Well-Being Index. The new questionnaire was found to be capable of detecting meaningful differences between respondents; spousal caregivers had worse QoL when the person with AD was confused (p < .001), could not be left alone (p < .001), did not recognize the caregiver (p < .001), was incontinent (p < .05), and wandered around the house (p = .01). CONCLUSIONS: The Alzheimer's Disease Patient Partners Life Impact Questionnaire (APPLIQue) is a questionnaire specific to spousal caregivers of people with AD. Data support its scaling assumptions and it exhibits excellent psychometric properties according to classical test theory. The questionnaire is recommended for use in intervention studies where the QoL of spousal caregivers is of interest.
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| 6. |
- Behm, K. T., et al.
(författare)
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A spectrometer for ultrashort gamma-ray pulses with photon energies greater than 10 MeV
- 2018
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 89:11
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 Author(s). We present a design for a pixelated scintillator based gamma-ray spectrometer for non-linear inverse Compton scattering experiments. By colliding a laser wakefield accelerated electron beam with a tightly focused, intense laser pulse, gamma-ray photons up to 100 MeV energies and with few femtosecond duration may be produced. To measure the energy spectrum and angular distribution, a 33 × 47 array of cesium-iodide crystals was oriented such that the 47 crystal length axis was parallel to the gamma-ray beam and the 33 crystal length axis was oriented in the vertical direction. Using an iterative deconvolution method similar to the YOGI code, modeling of the scintillator response using GEANT4 and fitting to a quantum Monte Carlo calculated photon spectrum, we are able to extract the gamma ray spectra generated by the inverse Compton interaction.
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| 7. |
- Cole, J. M., et al.
(författare)
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Experimental Evidence of Radiation Reaction in the Collision of a High-Intensity Laser Pulse with a Laser-Wakefield Accelerated Electron Beam
- 2018
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Ingår i: Physical Review X. - 2160-3308. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of energetic particles in strong electromagnetic fields can be heavily influenced by the energy loss arising from the emission of radiation during acceleration, known as radiation reaction. When interacting with a high-energy electron beam, today's lasers are sufficiently intense to explore the transition between the classical and quantum radiation reaction regimes. We present evidence of radiation reaction in the collision of an ultrarelativistic electron beam generated by laser-wakefield acceleration (μ 500 MeV) with an intense laser pulse (a0 > 10). We measure an energy loss in the postcollision electron spectrum that is correlated with the detected signal of hard photons (γ rays), consistent with a quantum description of radiation reaction. The generated γ rays have the highest energies yet reported from an all-optical inverse Compton scattering scheme, with critical energy > 30 MeV.
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| 8. |
- Hagell, Peter, et al.
(författare)
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Measuring the impact of caring for a spouse with Alzheimer's disease : validation of the Alzheimer’s patient partners life impact questionnaire (APPLIQue)
- 2018
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Ingår i: Journal of Applied Measurement. - : JAM Press. - 1529-7713. ; 19:3, s. 271-282
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Tidskriftsartikel (refereegranskat)abstract
- Alzheimer’s disease (AD) is the most common form of dementia, characterized by cognitive, psychiatric and behavioral symptoms and increasing dependency. Family members typically assume increasing caregiving responsibilities, with considerable quality of life (QoL) impact. This article describes the testing of a needs-based QoL questionnaire for AD family caregivers. Initial analyses according to Rasch measurement theory suggested that items applied to spousal rather than non-spousal caregivers. Following removal of non-spousal responders, a 25-item questionnaire was identified that exhibited acceptable model fit, a mean (SD) person location of 0.194 (1.42) logits, residual correlations ≤0.173 and absence of DIF by age, gender or administration. Reliability was 0.85. This new measure, the Alzheimer’s Patient Partners Life Impact Questionnaire (APPLIQue), may fill an important gap in assessing the impact of AD on spousal caregivers and outcomes of interventions aimed at caregivers as well as persons with AD.
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| 9. |
- Ridgers, C. P., et al.
(författare)
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Signatures of quantum effects on radiation reaction in laser-electron-beam collisions
- 2017
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Ingår i: Journal of Plasma Physics. - : Cambridge University Press (CUP). - 0022-3778 .- 1469-7807. ; 83:5
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Tidskriftsartikel (refereegranskat)abstract
- Two signatures of quantum effects on radiation reaction in the collision of a similar to GeV electron beam with a high intensity (>3 x 10(20) W cm(-2)) laser pulse have been considered. We show that the decrease in the average energy of the electron beam may be used to measure the Gaunt factor g for synchrotron emission. We derive an equation for the evolution of the variance in the energy of the electron beam in the quantum regime, i.e. quantum efficiency parameter eta (sic) 1. We show that the evolution of the variance may be used as a direct measure of the quantum stochasticity of the radiation reaction and determine the parameter regime where this is observable. For example, stochastic emission results in a 25 % increase in the standard deviation of the energy spectrum of a GeV electron beam, 1 fs after it collides with a laser pulse of intensity 10(21) W cm(-2). This effect should therefore be measurable using current high-intensity laser systems.
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| 10. |
- Svensson, K., et al.
(författare)
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Transverse expansion of the electron sheath during laser acceleration of protons
- 2017
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 24:12
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Tidskriftsartikel (refereegranskat)abstract
- The transverse expansion of the electrostatic sheath during target normal sheath acceleration of protons is investigated experimentally using a setup with two synchronized laser pulses. With the pulses spatially separated by less than three laser spot diameters, the resulting proton beam profiles become elliptical. By introducing a small intensity difference between the two pulses, the ellipses are rotated by a certain angle, except if the spatial separation of the two laser pulses is in the plane of incidence. The rotation angle is shown to depend on the relative intensity of the two pulses. The observed effects are found to require high temporal contrasts of the laser pulses. A simple model describing how the transverse shape of the electron sheath on the rear of the target depends on the relative intensity between the foci is presented. The model assumptions are verified, and the unknown dependence of the transverse extents of the sheaths are estimated self-consistently through a series of high resolution, two-dimensional particle-in-cell simulations. The results predicted by the model are also shown to be consistent with those obtained from the experiment.
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