| 1. |
- Bott, Lukas Thomas, et al.
(författare)
-
Coulomb dissociation of O-16 into He-4 and C-12
- 2023
-
Ingår i: NUCLEAR PHYSICS IN ASTROPHYSICS - X, NPA-X 2022. - : EDP Sciences. - 2100-014X. ; 279
-
Konferensbidrag (refereegranskat)abstract
- We measured the Coulomb dissociation of O-16 into He-4 and C-12 within the FAIR Phase-0 program at GSI Helmholtzzentrum fur Schwerionenforschung Darmstadt, Germany. From this we will extract the photon dissociation cross section O-16(alpha,gamma)C-12, which is the time reversed reaction to C-12(alpha,gamma)O-16. With this indirect method, we aim to improve on the accuracy of the experimental data at lower energies than measured so far. The expected low cross section for the Coulomb dissociation reaction and close magnetic rigidity of beam and fragments demand a high precision measurement. Hence, new detector systems were built and radical changes to the (RB)-B-3 setup were necessary to cope with the high-intensity O-16 beam. All tracking detectors were designed to let the unreacted O-16 ions pass, while detecting the C-12 and He-4.
|
|
| 2. |
- Alqedra, Mohammed K., et al.
(författare)
-
Optical coherence properties of Kramers' rare-earth ions at the nanoscale for quantum applications
- 2023
-
Ingår i: Physical Review B. - 2469-9950. ; 108:7
-
Tidskriftsartikel (refereegranskat)abstract
- Rare Earth (RE) ion doped nanomaterials are promising candidates for a range of quantum technology applications. Among RE ions, the so-called Kramers' ions possess spin transitions in the GHz range at low magnetic fields, which allows for high-bandwidth multimode quantum storage, fast qubit operations as well as interfacing with superconducting circuits. They also present relevant optical transitions in the infrared. In particular, Er3+ has an optical transition in the telecom band, while Nd3+ presents a high-emission-rate transition close to 890 nm. In this paper, we measure spectroscopic properties that are of relevance to using these materials in quantum technology applications. We find the inhomogeneous linewidth to be 10.7 GHz for Er3+ and 8.2 GHz for Nd3+, and the excited state lifetime T1 to be 13.68 ms for Er3+ and 540μs for Nd3+. We study the dependence of homogeneous linewidth on temperature for both samples, with the narrowest linewidth being 379 kHz (T2=839 ns) for Er3+ measured at 3 K, and 62 kHz (T2=5.14μs) for Nd3+ measured at 1.6 K. Further, we investigate time-dependent homogeneous linewidth broadening due to spectral diffusion and the dependence of the homogeneous linewidth on magnetic field to get additional clarity of mechanisms that can influence the coherence time. In light of our results, we discuss two applications: single qubit-state readout and a Fourier-limited single photon source.
|
|
| 3. |
- Bartholomew, John G., et al.
(författare)
-
High-resolution spectroscopic techniques for studying rare-earth ions in nanoparticles
- 2023
-
Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 257
-
Tidskriftsartikel (refereegranskat)abstract
- Rare-earth doped nanoparticles can exhibit narrow optical and spin linewidths at low temperatures. These outstanding properties for nanomaterials make them attractive for quantum technologies based on optically addressable spins such as quantum memories and computers. Although accurate linewidth measurements have been reported using, for example, spectral hole burning or photon echo techniques, so far they have been mostly restricted to large ensembles of particles. Being able to extend linewidths measurements to few and single particles is particularly important in view of their integration in nanophotonic devices. In this paper, we present techniques for determining inhomogeneous and homogeneous linewidths of small ensembles of rare-earth ions in doped nanoparticles with high signal-to-noise ratios for convenient integration times. Using these techniques we have observed property variations for particles from the same synthesis, a first step towards their optimization for applications in quantum technologies.
|
|
| 4. |
- Bengtsson, Alexander, et al.
(författare)
-
Comparison of contrast-to-noise ratios of different detection methods in ultrasound optical tomography
- 2022
-
Ingår i: Biomedical Optics Express. - 2156-7085. ; 13:9, s. 4834-4850
-
Tidskriftsartikel (refereegranskat)abstract
- Ultrasound optical tomography (UOT) is a hybrid imaging modality based on interaction between ultrasound and light, with a potential to extend optical imaging capabilities in biological tissues to depths of several centimeters. Several methods have been developed to detect the UOT signal. To better understand their potential for deep tissue imaging, we present a theoretical contrast-to-noise comparison between the spectral hole burning, single-shot off-axis holography, speckle contrast, and photorefractive detection methods for UOT. Our results indicate that spectral hole burning filters have the potential to reach the largest imaging depths. We find that digital off-axis holography and photorefractive detection can have good contrast-to-noise ratio at significant depths. The speckle contrast method has a smaller penetration depth comparatively.
|
|
| 5. |
- Bondza, Saskia, et al.
(författare)
-
A simple experimental method for measuring the thermal sensitivity of single-mode fibers
- 2020
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 91:10
-
Tidskriftsartikel (refereegranskat)abstract
- We present a simple technique to experimentally determine the optical-path length change with temperature for optical single-mode fibers. Standard single-mode fibers act as natural low-finesse cavities, with the Fresnel reflection of the straight cleaved surfaces being ∼3%, for the laser light coupled to them. By measuring the intensity variations due to interference of light reflected from the fiber front and end surfaces, while ramping the ambient temperature, the thermal sensitivity of the optical-path length of the fiber can be derived. Light was generated by a narrow linewidth, low drift laser. With our fairly short test fibers, we found that it was possible to reach a relative precision of the temperature sensitivity, compared to a reference fiber, on the 0.4%-2% scale and an absolute precision of 2%-5%, with the potential to improve both by an order of magnitude. The results for single-acrylate, dual-acrylate, and copper- and aluminum-coated fibers are presented. Values are compared with analytic models and results from a finite element method simulation. With the aid of these measurements, a simple fiber-interferometer, which is insensitive to thermal drifts, could be constructed.
|
|
| 6. |
- Chaudhry, Nadia, et al.
(författare)
-
Breast Cancer Diagnosis Using Extended-Wavelength–Diffuse Reflectance Spectroscopy (EW-DRS) : Proof of Concept in Ex Vivo Breast Specimens Using Machine Learning
- 2023
-
Ingår i: Diagnostics. - 2075-4418. ; 13:19, s. 1-12
-
Tidskriftsartikel (refereegranskat)abstract
- This study aims to investigate the feasibility of using diffuse reflectance spectroscopy (DRS) to distinguish malignant breast tissue from adjacent healthy tissue, and to evaluate if an extended-wavelength range (450–1550 nm) has an advantage over the standard wavelength range (450–900 nm). Multivariate statistics and machine learning algorithms, either linear discriminant analysis (LDA) or support vector machine (SVM) are used to distinguish the two tissue types in breast specimens (total or partial mastectomy) from 23 female patients with primary breast cancer. EW-DRS has a sensitivity of 94% and specificity of 91% as compared to a sensitivity of 40% and specificity of 71% using the standard wavelength range. The results suggest that DRS can discriminate between malignant and healthy breast tissue, with improved outcomes using an extended wavelength. It is also possible to construct a simple analytical model to improve the diagnostic performance of the DRS technique.
|
|
| 7. |
- Fortese, Fabricio, 1976-
(författare)
-
Early Determination of Arbitral Jurisdiction : Balancing efficacy, efficiency, and legitimacy of arbitration
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation examines the timing of judicial determination of jurisdictional disputes in the presence of an arbitration agreement. The analysis focuses on Article 8(1) of the UNCITRAL Model Law on International Commercial Arbitration (and Article II(3) of the New York Convention on the Recognition and Enforcement of Foreign Arbitral Awards). It circumscribes the discussions to a nuanced interpretative strategy.It is uncontroversial that national courts have the authority to decide, conclusively, disputes on arbitral jurisdiction. It is common ground that arbitrators, too, have the authority to rule on their own jurisdiction, subject to judicial control. This is known as the principle of competence-competence, which is widely recognised in arbitration legislation, institutional rules, and practice. The critical research question that this dissertation deals with is whether national courts should (or could) conclusively determine arbitral jurisdiction before or after the arbitrators have preliminarily determined that controversy.This dissertation does not question who has the authority to settle jurisdictional disputes (conflict of jurisdictions). The assumption is that both, judges and arbitrators, enjoy such decision-making power. Instead, this research is about when (timing) a court should exercise that authority with conclusive effects.This work examines and answers the when question from an autonomous legal-interpretation perspective, detached from a given State's law, concepts, and rules. Its theoretical framework is specific to the Model Law and national arbitration laws that have adopted it without deviating from it – at least not from the wording of Article 8.
|
|
| 8. |
- Gobel, K., et al.
(författare)
-
Coulomb dissociation of 16O into 4He and 12C
- 2020
-
Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 1668:1
-
Konferensbidrag (refereegranskat)abstract
- We measured the Coulomb dissociation of 16O into 4He and 12C at the R3B setup in a first campaign within FAIR Phase 0 at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt. The goal was to improve the accuracy of the experimental data for the 12C(a,?)16O fusion reaction and to reach lower center-ofmass energies than measured so far. The experiment required beam intensities of 109 16O ions per second at an energy of 500 MeV/nucleon. The rare case of Coulomb breakup into 12C and 4He posed another challenge: The magnetic rigidities of the particles are so close because of the same mass-To-charge-number ratio A/Z = 2 for 16O, 12C and 4He. Hence, radical changes of the R3B setup were necessary. All detectors had slits to allow the passage of the unreacted 16O ions, while 4He and 12C would hit the detectors' active areas depending on the scattering angle and their relative energies. We developed and built detectors based on organic scintillators to track and identify the reaction products with sufficient precision.
|
|
| 9. |
|
|
| 10. |
- Horvath, Sebastian P., et al.
(författare)
-
Noise-free on-demand atomic frequency comb quantum memory
- 2021
-
Ingår i: Physical Review Research. - 2643-1564. ; 3:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present an extension of the atomic frequency comb protocol that utilizes the Stark effect to perform noise-free, on-demand, control. An experimental realization of this protocol was implemented in the Pr3+:Y2SiO5 solid-state system, and a recall efficiency of 38% for a 0.8 μs storage time was achieved. Experiments were performed with both bright pulses as well as weak-coherent states, the latter achieving a signal-to-noise ratio of 570±120 using input pulses with an average photon number of ∼0.1. The principal limitation for a longer storage time was found to be the minimum peak width attainable for Pr3+:Y2SiO5. We employ an adaptation of an established atomic frequency comb model to investigate an on-demand, wide-bandwidth, memory based on Eu3+:Y2SiO5. From this, we determine that a storage time as long as 100 μs may be practical even without recourse to spin-wave storage.
|
|
