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Sökning: WFRF:(Ohshima Takeshi)

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1.
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2.
  • Anderson, Christopher P., et al. (författare)
  • Electrical and optical control of single spins integrated in scalable semiconductor devices
  • 2019
  • Ingår i: Science. - : AMER ASSOC ADVANCEMENT SCIENCE. - 0036-8075 .- 1095-9203. ; 366:6470, s. 1225-
  • Tidskriftsartikel (refereegranskat)abstract
    • Spin defects in silicon carbide have the advantage of exceptional electron spin coherence combined with a near-infrared spin-photon interface, all in a material amenable to modern semiconductor fabrication. Leveraging these advantages, we integrated highly coherent single neutral divacancy spins in commercially available p-i-n structures and fabricated diodes to modulate the local electrical environment of the defects. These devices enable deterministic charge-state control and broad Stark-shift tuning exceeding 850 gigahertz. We show that charge depletion results in a narrowing of the optical linewidths by more than 50-fold, approaching the lifetime limit. These results demonstrate a method for mitigating the ubiquitous problem of spectral diffusion in solid-state emitters by engineering the electrical environment while using classical semiconductor devices to control scalable, spin-based quantum systems.
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3.
  • Anderson, Christopher P., et al. (författare)
  • Five-second coherence of a single spin with single-shot readout in silicon carbide
  • 2022
  • Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 8:5
  • Tidskriftsartikel (refereegranskat)abstract
    • An outstanding hurdle for defect spin qubits in silicon carbide (SiC) is single-shot readout, a deterministic measurement of the quantum state. Here, we demonstrate single-shot readout of single defects in SiC via spin-to-charge conversion, whereby the defects spin state is mapped onto a long-lived charge state. With this technique, we achieve over 80% readout fidelity without pre- or postselection, resulting in a high signal-to-noise ratio that enables us to measure long spin coherence times. Combined with pulsed dynamical decoupling sequences in an isotopically purified host material, we report single-spin T-2 > 5 seconds, over two orders of magnitude greater than previously reported in this system. The mapping of these coherent spin states onto single charges unlocks both single-shot readout for scalable quantum nodes and opportunities for electrical readout via integration with semiconductor devices.
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4.
  • Beyer, Franziska, et al. (författare)
  • Metastable defects in low-energy electron irradiated n-type 4H-SiC
  • 2010
  • Ingår i: Materials Science Forum, Vols. 645-648. - : Trans Tech Publications. ; , s. 435-438
  • Konferensbidrag (refereegranskat)abstract
    • After low-energy electron irradiation of epitaxial n-type 4H-SiC, the DUES peak amplitudes. of the defects Z(1/2) and EH6/7, which were already observed in as-grown layers, increased and the commonly found peaks EH1 and EH3 appeared. The bistable M-center, previously seen in high-energy proton implanted 4H-SiC, was detected. New bistable defects, the EB-centers, evolved after annealing out of the M-center, and EF3. The reconfiguration energies for one of the two EB-centers were determined to be about 0.96 eV for both transitions: from configuration I to II and from configuration II to I. Since low-energy electron irradiation (less than220 keV) affects mainly the carbon atom in SiC, both the M- and EB-centers are likely to be carbon related defects.
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5.
  • Beyer, Franziska, et al. (författare)
  • Observation of Bistable Defects in Electron Irradiated N-Type 4H-SiC
  • 2011
  • Ingår i: <em>Materials Science Forum Vols. 679-680 (2011) pp 249-252</em>. - : Trans Tech Publications Inc.. ; , s. 249-252
  • Konferensbidrag (refereegranskat)abstract
    • DLTS measurements show bistable behavior of the previously reported EH5 peak in low- and high-energy electron irradiation 4H-SiC. Both reconfiguration processes (A ! B and B ! A) take place above 700 ±C. By isothermal annealing, the reconfiguration rates were determined and the reconfiguration energy was calculated to EA = 2.4±0.2 eV. Since the defect is present already after low-energy electron irradiation, which mainly affects the C atom in SiC, the EH5 peak may be related to defects associated with C-vacancies or C-interstitials.
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6.
  • Bourassa, Alexandre, et al. (författare)
  • Entanglement and control of single nuclear spins in isotopically engineered silicon carbide
  • 2020
  • Ingår i: Nature Materials. - : NATURE RESEARCH. - 1476-1122 .- 1476-4660. ; 19:12, s. 1319-1325
  • Tidskriftsartikel (refereegranskat)abstract
    • Isotope engineering of silicon carbide leads to control of nuclear spins associated with single divacancy centres and extended electron spin coherence. Nuclear spins in the solid state are both a cause of decoherence and a valuable resource for spin qubits. In this work, we demonstrate control of isolated(29)Si nuclear spins in silicon carbide (SiC) to create an entangled state between an optically active divacancy spin and a strongly coupled nuclear register. We then show how isotopic engineering of SiC unlocks control of single weakly coupled nuclear spins and present an ab initio method to predict the optimal isotopic fraction that maximizes the number of usable nuclear memories. We bolster these results by reporting high-fidelity electron spin control (F = 99.984(1)%), alongside extended coherence times (Hahn-echoT(2) = 2.3 ms, dynamical decouplingT(2)(DD) > 14.5 ms), and a >40-fold increase in Ramsey spin dephasing time (T-2*) from isotopic purification. Overall, this work underlines the importance of controlling the nuclear environment in solid-state systems and links single photon emitters with nuclear registers in an industrially scalable material.
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7.
  • Christle, David J., et al. (författare)
  • Isolated electron spins in silicon carbide with millisecond coherence times
  • 2015
  • Ingår i: Nature Materials. - : Nature Publishing Group. - 1476-1122 .- 1476-4660. ; 14:2, s. 160-163
  • Tidskriftsartikel (refereegranskat)abstract
    • The elimination of defects from SiC has facilitated its move to the forefront of the optoelectronics and power-electronics industries(1). Nonetheless, because certain SiC defects have electronic states with sharp optical and spin transitions, they are increasingly recognized as a platform for quantum information and nanoscale sensing(2-16). Here, we show that individual electron spins in high-purity monocrystalline 4H-SiC can be isolated and coherently controlled. Bound to neutral divacancy defects(2,3), these states exhibit exceptionally long ensemble Hahn-echo spin coherence times, exceeding 1 ms. Coherent control of single spins in a material amenable to advanced growth and microfabrication techniques is an exciting route towards wafer-scale quantum technologies.
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8.
  • Christle, David J., et al. (författare)
  • Isolated Spin Qubits in SiC with a High-Fidelity Infrared Spin-to-Photon Interface
  • 2017
  • Ingår i: Physical Review X. - : AMER PHYSICAL SOC. - 2160-3308. ; 7:2
  • Tidskriftsartikel (refereegranskat)abstract
    • The divacancies in SiC are a family of paramagnetic defects that show promise for quantum communication technologies due to their long-lived electron spin coherence and their optical addressability at near-telecom wavelengths. Nonetheless, a high-fidelity spin-photon interface, which is a crucial prerequisite for such technologies, has not yet been demonstrated. Here, we demonstrate that such an interface exists in isolated divacancies in epitaxial films of 3C-SiC and 4H-SiC. Our data show that divacancies in 4H-SiC have minimal undesirable spin mixing, and that the optical linewidths in our current sample are already similar to those of recent remote entanglement demonstrations in other systems. Moreover, we find that 3C-SiC divacancies have a millisecond Hahn-echo spin coherence time, which is among the longest measured in a naturally isotopic solid. The presence of defects with these properties in a commercial semiconductor that can be heteroepitaxially grown as a thin film on Si shows promise for future quantum networks based on SiC defects.
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9.
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10.
  • Davidsson, Joel, et al. (författare)
  • Identification of divacancy and silicon vacancy qubits in 6H-SiC
  • 2019
  • Ingår i: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 114:11
  • Tidskriftsartikel (refereegranskat)abstract
    • Point defects in semiconductors are relevant for use in quantum technologies as room temperature qubits and single photon emitters. Among suggested defects for these applications are the negatively charged silicon vacancy and the neutral divacancy in SiC. The possible nonequivalent configurations of these defects have been identified in 4H-SiC, but for 6H-SiC, the work is still in progress. In this paper, we identify the different configurations of the silicon vacancy and the divacancy defects to each of the V1-V3 and the QL1-QL6 color centers in 6H-SiC, respectively. We accomplish this by comparing the results from ab initio calculations with experimental measurements for the zero-phonon line, hyperfine tensor, and zero-field splitting. Published under license by AIP Publishing.
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11.
  • de las Casas, Charles F., et al. (författare)
  • Stark tuning and electrical charge state control of single divacancies in silicon carbide
  • 2017
  • Ingår i: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 111:26
  • Tidskriftsartikel (refereegranskat)abstract
    • Neutrally charged divacancies in silicon carbide (SiC) are paramagnetic color centers whose long coherence times and near-telecom operating wavelengths make them promising for scalable quantum communication technologies compatible with existing fiber optic networks. However, local strain inhomogeneity can randomly perturb their optical transition frequencies, which degrades the indistinguishability of photons emitted from separate defects and hinders their coupling to optical cavities. Here, we show that electric fields can be used to tune the optical transition frequencies of single neutral divacancy defects in 4H-SiC over a range of several GHz via the DC Stark effect. The same technique can also control the charge state of the defect on microsecond timescales, which we use to stabilize unstable or non-neutral divacancies into their neutral charge state. Using fluorescence-based charge state detection, we show that both 975 nm and 1130 nm excitation can prepare their neutral charge state with near unity efficiency. (C) 2017 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons. org/licenses/by/4.0/).
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12.
  • Duc, Tran Thien, et al. (författare)
  • Capture cross section of electron-irradiation-induced defects in bulk GaN grown by halide vapor phase epitaxy
  • 2014
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Electron-irradiation-induced defects in GaN grown by halide vapor phase epitaxy is studied by deep level transient spectroscopy in which the capture cross section and its temperature dependence of the deep levels was determined by the filling pulse method. Before irradiation, one trap level, labelled ET4 (EC – 0.244 eV), was observed. After performing electron irradiation with an energy of 2 MeV at a fluence of 5 × 1016 cm-2, four deep trap levels, labelled ET1 (EC – 0.178 eV), ET2 (EC – 0.181 eV), ET3 (EC – 0.256 eV) and ET5 appeared. After annealing at 650K for 2 hours, only two irradiation induced deep levels, ET1 and ET3, were observed. By varying the rate windows, the temperature dependence of the capture cross section of the two deep levels ET1 and ET2 and ET3 was studied. The temperature behavior of ET2 and ET3 capture cross section is independent on temperature whereas the capture cross section of the deep level ET1 depends strongly on the temperature. It is suggested that electron capturing is govern by a multiphonon process to the level ET1.
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13.
  • Duc, Tran Thien, et al. (författare)
  • Radiation-induced defects in GaN bulk grown by halide vapor phase epitaxy
  • 2014
  • Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 105:10, s. 102103-
  • Tidskriftsartikel (refereegranskat)abstract
    • Defects induced by electron irradiation in thick free-standing GaN layers grown by halide vapor phase epitaxy were studied by deep level transient spectroscopy. In as-grown materials, six electron traps, labeled D2 (E-C-0.24 eV), D3 (E-C-0.60 eV), D4 (E-C-0.69 eV), D5 (E-C-0.96 eV), D7 (E-C-1.19 eV), and D8, were observed. After 2MeV electron irradiation at a fluence of 1 x 10(14) cm(-2), three deep electron traps, labeled D1 (E-C-0.12 eV), D5I (E-C-0.89 eV), and D6 (E-C-1.14 eV), were detected. The trap D1 has previously been reported and considered as being related to the nitrogen vacancy. From the annealing behavior and a high introduction rate, the D5I and D6 centers are suggested to be related to primary intrinsic defects.
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14.
  • Duc Tran, Thien, et al. (författare)
  • Deep levels in as-grown and electron-irradiated n-type GaN studied by deep level transient spectroscopy and minority carrier transient spectroscopy
  • 2016
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 119:9
  • Tidskriftsartikel (refereegranskat)abstract
    • By minority carrier transient spectroscopy on as-grown n-type bulk GaN produced by halide vapor phase epitaxy (HVPE) one hole trap labelled H1 (EV + 0.34 eV) has been detected. After 2 MeV-energy electron irradiation, the concentration of H1 increases and at fluences higher than 5×1014 cm-2, a second hole trap labelled H2 is observed. Simultaneously, the concentration of two electron traps, labelled T1 (EC - 0.12 eV) and T2 (EC - 0.23 eV) increases. By studying the increase of the concentration versus electron irradiation fluences, the introduction rate of T1 and T2 using 2 MeV-energy electrons was determined to 7X10-3 cm-1 and 0.9 cm-1, respectively. Due to the low introduction rate of T1 and the low threading dislocation density in the HVPE bulk GaN material, it is suggested that the defect is associated with a primary defect decorating extended structural defects. The high introduction rate of the trap H1 suggests that the H1 defect is associated with a primary intrinsic defect or a complex.
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15.
  • Duc Tran, Thien, et al. (författare)
  • Electronic properties of defects in high-fluence electron irradiated bulk GaN
  • 2016
  • Ingår i: Physica status solidi. B, Basic research. - : John Wiley & Sons. - 0370-1972 .- 1521-3951. ; 253:3, s. 521-526
  • Tidskriftsartikel (refereegranskat)abstract
    • Using deep level transient spectroscopy, deep levels and capture cross sections of defects introduced by high-fluence electron irradiation of thick halide vapour phase epitaxy grown GaN has been studied. After irradiation with 2 MeV electrons to a high-fluence of 5×1016 cm-2, four deep trap levels, labelled T1 (EC – 0.13 eV), T2 (EC – 0.18 eV), T3 (EC – 0.26 eV) T4 and a broad band of peaks consisting of at least two levels could be observed. These defects, except T1 and T3, were annealed out after annealing at 650 K for 2 hours. The capture cross section is found to be temperature independent for T2 and T3, while T1 shows an decresing capture cross section with increasing temperature, suggesting that electron capturing to this deep level is governed by a cascade capturing process.
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16.
  • Duc Tran, Thien, et al. (författare)
  • Thermal behavior of irradiation-induced-deep levels in bulk GaN
  • 2015
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Bulk GaN grown by halide vapor phase epitaxy and irradiated by 2 MeV electrons at a fluence of 5×1016 cm-2 were studied by deep level transient spectroscopy. After irradiation, two new peaks labelled D0 (EC – 0.18 eV) and D1 (EC – 0.13 eV) are observed. From isochronal annealing studies in the temperature range of 350 - 600 K, it is observed that peak D0 is completely annealed out already at 550 K while the broad peak D1 has a more complex annealing behavior. The concentration of D1 is decreasing during annealing and its peak position is shifted to higher temperatures, until a relatively stable peak labelled D2 (EC – 0.24 eV) is formed. From an isothermal annealing study of D2, it is concluded that the annealing process can be described by a first order annealing process with an activation energy and prefactor of 1.2 eV and 6.6 × 105 s-1, respectively. From the large pre-factor it is concluded that the annihilation of D2 is governed by a long-range migration process. From its annealing behavior, it is suggested that trap D2 may be related to the VGa.
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17.
  • Ivády, Viktor, et al. (författare)
  • Identification of Si-vacancy related room-temperature qubits in 4H silicon carbide
  • 2017
  • Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 96:16
  • Tidskriftsartikel (refereegranskat)abstract
    • The identification of a microscopic configuration of point defects acting as quantum bits is a key step in the advance of quantum information processing and sensing. Among the numerous candidates, silicon-vacancy related centers in silicon carbide (SiC) have shown remarkable properties owing to their particular spin-3/2 ground and excited states. Although, these centers were observed decades ago, two competing models, the isolated negatively charged silicon vacancy and the complex of negatively charged silicon vacancy and neutral carbon vacancy [Phys. Rev. Lett. 115, 247602 (2015)], are still argued as an origin. By means of high-precision first-principles calculations and high-resolution electron spin resonance measurements, we here unambiguously identify the Si-vacancy related qubits in hexagonal SiC as isolated negatively charged silicon vacancies. Moreover, we identify the Si-vacancy qubit configurations that provide room-temperature optical readout.
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18.
  • Ivády, Viktor, et al. (författare)
  • Photoluminescence at the ground-state level anticrossing of the nitrogen-vacancy center in diamond: A comprehensive study
  • 2021
  • Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 103:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The nitrogen-vacancy center (NV center) in diamond at magnetic fields corresponding to the ground-state level anticrossing (GSLAC) region gives rise to rich photoluminescence (PL) signals due to the vanishing energy gap between the electron spin states, which enables for a broad variety of environmental couplings to have an effect on the NV centers luminescence. Previous works have addressed several aspects of the GSLAC photoluminescence, however, a comprehensive analysis of the GSLAC signature of NV ensembles in different spin environments at various external fields is missing. Here we employ a combination of experiments and recently developed numerical methods to investigate in detail the effects of transverse electric and magnetic fields, strain, P1 centers, NV centers, and the C-13 nuclear spins on the GSLAC photoluminescence. Our comprehensive analysis provides a solid ground for advancing various microwave-free applications at the GSLAC, including but not limited to magnetometry, spectroscopy, dynamic nuclear polarization (DNP), and nuclear magnetic resonance (NMR) detection. We demonstrate that not only the most abundant (NV)-N-14 center but the (NV)-N-15 can also be utilized in such applications.
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19.
  • Kitade, Yujiro, et al. (författare)
  • Antarctic Bottom Water production from the Vincennes Bay Polynya, East Antarctica
  • 2014
  • Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 41:10, s. 3528-3534
  • Tidskriftsartikel (refereegranskat)abstract
    • One year moorings at depths greater than 3000m on the continental slope off Vincennes Bay, East Antarctica, reveal the cold (<-0.5 degrees C) and fresh (<34.64) signals of newly formed Antarctic Bottom Water (AABW). The signal appeared in June, 3 months after the onset of active sea-ice production in the nearby Vincennes Bay Polynya (VBP). The AABW signal continued for about 5 months at two moorings, with 1 month delay at the western site further downstream. Ship-based hydrographic data are in agreement, detecting the westward spread of new AABW over the continental slope from VBP. On the continental shelf, Dense Shelf Water (DSW) formation is observed by instrumented seals, in and around the VBP during autumn, and we estimate its transport to be 0.16 +/- 0.07 (x 106m3s-1). We conclude that the DSW formed in this region, albeit from a modest amount of sea-ice production, nonetheless contributes to the upper layer of AABW in Australian-Antarctic Basin.
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20.
  • Liu, Di, et al. (författare)
  • The silicon vacancy centers in SiC: determination of intrinsic spin dynamics for integrated quantum photonics
  • 2024
  • Ingår i: NPJ QUANTUM INFORMATION. - : NATURE PORTFOLIO. - 2056-6387. ; 10:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The negatively charged silicon vacancy center (VSi-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\rm{V}}}_{{\rm{Si}}}<^>{-}$$\end{document}) in silicon carbide (SiC) is an emerging color center for quantum technology covering quantum sensing, communication, and computing. Yet, limited information currently available on the internal spin-optical dynamics of these color centers prevents us from achieving the optimal operation conditions and reaching the maximum performance especially when integrated within quantum photonics. Here, we establish all the relevant intrinsic spin dynamics of the VSi-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\rm{V}}}_{{\rm{Si}}}<^>{-}$$\end{document} center at cubic lattice site (V2) in 4H-SiC by an in-depth electronic fine structure modeling including the intersystem-crossing and deshelving mechanisms. With carefully designed spin-dependent measurements, we obtain all the previously unknown spin-selective radiative and non-radiative decay rates. To showcase the relevance of our work for integrated quantum photonics, we use the obtained rates to propose a realistic implementation of time-bin entangled multi-photon GHZ and cluster state generation. We find that up to three-photon GHZ or cluster states are readily within reach using the existing nanophotonic cavity technology.
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21.
  • Lukin, Daniil M., et al. (författare)
  • Spectrally reconfigurable quantum emitters enabled by optimized fast modulation
  • 2020
  • Ingår i: NPJ QUANTUM INFORMATION. - : NATURE PUBLISHING GROUP. - 2056-6387. ; 6:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The ability to shape photon emission facilitates strong photon-mediated interactions between disparate physical systems, thereby enabling applications in quantum information processing, simulation and communication. Spectral control in solid state platforms such as color centers, rare earth ions, and quantum dots is particularly attractive for realizing such applications on-chip. Here we propose the use of frequency-modulated optical transitions for spectral engineering of single photon emission. Using a scattering-matrix formalism, we find that a two-level system, when modulated faster than its optical lifetime, can be treated as a single-photon source with a widely reconfigurable photon spectrum that is amenable to standard numerical optimization techniques. To enable the experimental demonstration of this spectral control scheme, we investigate the Stark tuning properties of the silicon vacancy in silicon carbide, a color center with promise for optical quantum information processing technologies. We find that the silicon vacancy possesses excellent spectral stability and tuning characteristics, allowing us to probe its fast modulation regime, observe the theoretically-predicted two-photon correlations, and demonstrate spectral engineering. Our results suggest that frequency modulation is a powerful technique for the generation of new light states with unprecedented control over the spectral and temporal properties of single photons.
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22.
  • Lukin, Daniil M., et al. (författare)
  • Two-Emitter Multimode Cavity Quantum Electrodynamics in Thin-Film Silicon Carbide Photonics
  • 2023
  • Ingår i: Physical Review X. - : American Physical Society. - 2160-3308. ; 13:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Color centers are point defects in crystals that can provide an optical interface to a long-lived spin state for distributed quantum information processing applications. An outstanding challenge for color center quantum technologies is the integration of optically coherent emitters into scalable thin-film photonics, a prerequisite for large-scale photonics integration of color centers within a commercial foundry process. Here, we report on the integration of near-transform-limited silicon vacancy (VSi) defects into microdisk resonators fabricated in a CMOS-compatible 4H-silicon carbide-on-insulator platform. We demonstrate a single-emitter cooperativity of up to 0.8 as well as optical superradiance from a pair of color centers coupled to the same cavity mode. We investigate the effect of multimode interference on the photon scattering dynamics from this multiemitter cavity quantum electrodynamics system. These results are crucial for the development of quantum networks in silicon carbide and bridge the classical-quantum photonics gap by uniting optically coherent spin defects with wafer-scalable, state-of-the-art photonics.
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23.
  • Magnusson, Björn, et al. (författare)
  • Excitation properties of the divacancy in 4H-SiC
  • 2018
  • Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 98:19
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate the quenching of the photoluminescence (PL) from the divacancy defect in 4H-SiC consisting of a nearest-neighbor silicon and carbon vacancies. The quenching occurs only when the PL is excited below certain photon energies (thresholds), which differ for the four different inequivalent divacancy configurations in 4H-SiC. An accurate theoretical ab initio calculation for the charge-transfer levels of the divacancy shows very good agreement between the position of the (0/-) level with respect to the conduction band for each divacancy configuration and the corresponding experimentally observed threshold, allowing us to associate the PL decay with conversion of the divacancy from neutral to negative charge state due to capture of electrons photoionized from other defects (traps) by the excitation. Electron paramagnetic resonance measurements are conducted in the dark and under excitation similar to that used in the PL experiments and shed light on the possible origin of traps in the different samples. A simple model built on this concept agrees well with the experimentally observed decay curves.
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24.
  • Miao, Kevin C., et al. (författare)
  • Electrically driven optical interferometry with spins in silicon carbide
  • 2019
  • Ingår i: Science Advances. - : AMER ASSOC ADVANCEMENT SCIENCE. - 2375-2548. ; 5:11
  • Tidskriftsartikel (refereegranskat)abstract
    • Interfacing solid-state defect electron spins to other quantum systems is an ongoing challenge. The ground-state spins weak coupling to its environment not only bestows excellent coherence properties but also limits desired drive fields. The excited-state orbitals of these electrons, however, can exhibit stronger coupling to phononic and electric fields. Here, we demonstrate electrically driven coherent quantum interference in the optical transition of single, basally oriented divacancies in commercially available 4H silicon carbide. By applying microwave frequency electric fields, we coherently drive the divacancys excited-state orbitals and induce Landau-Zener-Stuckelberg interference fringes in the resonant optical absorption spectrum. In addition, we find remarkably coherent optical and spin subsystems enabled by the basal divacancys symmetry. These properties establish divacancies as strong candidates for quantum communication and hybrid system applications, where simultaneous control over optical and spin degrees of freedom is paramount.
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25.
  • Morioka, Naoya, et al. (författare)
  • Spin-controlled generation of indistinguishable and distinguishable photons from silicon vacancy centres in silicon carbide
  • 2020
  • Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 11:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Quantum systems combining indistinguishable photon generation and spin-based quantum information processing are essential for remote quantum applications and networking. However, identification of suitable systems in scalable platforms remains a challenge. Here, we investigate the silicon vacancy centre in silicon carbide and demonstrate controlled emission of indistinguishable and distinguishable photons via coherent spin manipulation. Using strong off-resonant excitation and collecting zero-phonon line photons, we show a two-photon interference contrast close to 90% in Hong-Ou-Mandel type experiments. Further, we exploit the systems intimate spin-photon relation to spin-control the colour and indistinguishability of consecutively emitted photons. Our results provide a deep insight into the systems spin-phonon-photon physics and underline the potential of the industrially compatible silicon carbide platform for measurement-based entanglement distribution and photonic cluster state generation. Additional coupling to quantum registers based on individual nuclear spins would further allow for high-level network-relevant quantum information processing, such as error correction and entanglement purification. Defects in silicon carbide can act as single photon sources that also have the benefit of a host material that is already used in electronic devices. Here the authors demonstrate that they can control the distinguishability of the emitted photons by changing the defect spin state.
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26.
  • Morioka, Naoya, et al. (författare)
  • Spin-Optical Dynamics and Quantum Efficiency of a Single V1 Center in Silicon Carbide
  • 2022
  • Ingår i: Physical Review Applied. - : AMER PHYSICAL SOC. - 2331-7019. ; 17:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Color centers in silicon carbide are emerging candidates for distributed spin-based quantum applications due to the scalability of host materials and the demonstration of integration into nanophotonic resonators. Recently, silicon vacancy centers in silicon carbide have been identified as a promising system with excellent spin and optical properties. Here, we fully study the spin-optical dynamics of the single silicon vacancy center at hexagonal lattice sites, namely V1, in 4H-polytype silicon carbide. By utilizing resonant and above-resonant sublifetime pulsed excitation, we determine spin-dependent excited-state lifetimes and intersystem-crossing rates. Our approach to inferring the intersystem-crossing rates is based on all-optical pulsed initialization and readout scheme, and is applicable to spin-active color centers with similar dynamics models. In addition, the optical transition dipole strength and the quantum efficiency of V1 defect are evaluated based on coherent optical Rabi measurement and local-field calibration employing electric field simulation. The measured rates well explain the results of spin-state polarization dynamics, and we further discuss the altered photoemission dynamics in resonant enhancement structures such as radiative lifetime shortening and Purcell enhancement. By providing a thorough description of the V1 center???s spin-optical dynamics, our work provides deep understanding of the system, which guides implementations of scalable quantum applications based on silicon vacancy centers in silicon carbide.
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27.
  • Morokuma, Tomoki, et al. (författare)
  • OISTER optical and near-infrared monitoring observations of peculiar radio-loud active galactic nucleus SDSSJ110006.07+442144.3
  • 2017
  • Ingår i: Nippon Tenmon Gakkai obun kenkyu hokoku. - : Oxford University Press (OUP). - 0004-6264. ; 69:5
  • Tidskriftsartikel (refereegranskat)abstract
    • We present monitoring campaign observations at optical and near-infrared (NIR) wavelengths for a radio-loud active galactic nucleus (AGN) at z = 0.840, SDSSJ110006.07+442144.3 (hereafter, J1100+4421), which was identified during a flare phase in late 2014 February. The campaigns consist of three intensive observing runs from the discovery to 2015 March, mostly within the scheme of the OISTER collaboration. Optical-NIR light curves and simultaneous spectral energy distributions (SEDs) are obtained. Our measurements show the strongest brightening in 2015 March. We found that the optical-NIR SEDs of J1100+4421 show an almost steady shape despite the large and rapid intranight variability. This constant SED shape is confirmed to extend to similar to 5 mu m in the observed frame using the archival WISE data. Given the lack of absorption lines and the steep power-law spectrum of alpha(upsilon) similar to -1.4, where f(v) proportional to v(alpha upsilon), synchrotron radiation by a relativistic jet with no or small contributions from the host galaxy and the accretion disk seemsmost plausible as an optical-NIR emission mechanism. The steep optical-NIR spectral shape and the large amplitude of variability are consistent with this object being a low.peak jet-dominated AGN. In addition, sub-arcsecond resolution optical imaging data taken with Subaru Hyper Suprime-Cam does not show a clear extended component and the spatial scales are significantly smaller than the large extensions detected at radio wavelengths. The optical spectrum of a possible faint companion galaxy does not show any emission lines at the same redshift, and hence a merging hypothesis for this AGN-related activity is not supported by our observations.
  •  
28.
  • Nagy, Roland, et al. (författare)
  • High-fidelity spin and optical control of single silicon-vacancy centres in silicon carbide
  • 2019
  • Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 10
  • Tidskriftsartikel (refereegranskat)abstract
    • Scalable quantum networking requires quantum systems with quantum processing capabilities. Solid state spin systems with reliable spin-optical interfaces are a leading hardware in this regard. However, available systems suffer from large electron-phonon interaction or fast spin dephasing. Here, we demonstrate that the negatively charged silicon-vacancy centre in silicon carbide is immune to both drawbacks. Thanks to its (4)A(2) symmetry in ground and excited states, optical resonances are stable with near-Fourier-transform-limited linewidths, allowing exploitation of the spin selectivity of the optical transitions. In combination with millisecond-long spin coherence times originating from the high-purity crystal, we demonstrate high-fidelity optical initialization and coherent spin control, which we exploit to show coherent coupling to single nuclear spins with similar to 1 kHz resolution. The summary of our findings makes this defect a prime candidate for realising memory-assisted quantum network applications using semiconductor-based spin-to-photon interfaces and coherently coupled nuclear spins.
  •  
29.
  • Nagy, Roland, et al. (författare)
  • Narrow inhomogeneous distribution of spin-active emitters in silicon carbide
  • 2021
  • Ingår i: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 118:14
  • Tidskriftsartikel (refereegranskat)abstract
    • Optically active solid-state spin registers have demonstrated their unique potential in quantum computing, communication, and sensing. Realizing scalability and increasing application complexity require entangling multiple individual systems, e.g., via photon interference in an optical network. However, most solid-state emitters show relatively broad spectral distributions, which hinders optical interference experiments. Here, we demonstrate that silicon vacancy centers in semiconductor silicon carbide (SiC) provide a remarkably small natural distribution of their optical absorption/emission lines despite an elevated defect concentration of approximate to 0.43 mu m - 3. In particular, without any external tuning mechanism, we show that only 13 defects have to be investigated until at least two optical lines overlap within the lifetime-limited linewidth. Moreover, we identify emitters with overlapping emission profiles within diffraction-limited excitation spots, for which we introduce simplified schemes for the generation of computationally relevant Greenberger-Horne-Zeilinger and cluster states. Our results underline the potential of the CMOS-compatible SiC platform toward realizing networked quantum technology applications.
  •  
30.
  • Nagy, Roland, et al. (författare)
  • Quantum Properties of Dichroic Silicon Vacancies in Silicon Carbide
  • 2018
  • Ingår i: Physical Review Applied. - 2331-7019. ; 9:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Although various defect centers have displayed promise as either quantum sensors, single photon emitters, or light-matter interfaces, the search for an ideal defect with multifunctional ability remains open. In this spirit, we study the dichroic silicon vacancies in silicon carbide that feature two well-distinguishable zero-phonon lines and analyze the quantum properties in their optical emission and spin control. We demonstrate that this center combines 40% optical emission into the zero-phonon lines showing the contrasting difference in optical properties with varying temperature and polarization, and a 100% increase in the fluorescence intensity upon the spin resonance, and long spin coherence time of their spin-3/2 ground states up to 0.6 ms. These results single out this defect center as a promising system for spin-based quantum technologies.
  •  
31.
  • Nakane, Hiroki, et al. (författare)
  • Deep levels related to the carbon antisite-vacancy pair in 4H-SiC
  • 2021
  • Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 130:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Photo-induced current transient spectroscopy (PICTS) and electron paramagnetic resonance (EPR) are used to study irradiation-induced defects in high-purity semi-insulating (HPSI) 4H-SiC. Several deep levels with the ionization energy ranging from 0.1 to similar to 1.1 eV have been observed in irradiated and annealed samples by PICTS. Among these, two deep levels, labeled E370 and E700 at similar to 0.72 and similar to 1.07 eV below the conduction band, respectively, are detected after high-temperature annealing. The appearance and disappearance of these two deep levels and the EPR signal of the positive C antisite-vacancy pair (CSiVC+) in the sample annealed at 1000 and 1200 degrees C, respectively, are well correlated. Based on data from PICTS and EPR and the energies predicted by previous calculations for different charge states of dominant intrinsic defects, the E370 and E700 levels are suggested to be related to the charge transition levels (0|-) and (+|0), respectively, of the C antisite-vacancy pair. The activation energy of E-a similar to 1.1 eV in commercial HPSI 4H-SiC materials is, therefore, reassigned to be related to the single donor (+|0) level of CSiVC.
  •  
32.
  • Nguyen, Son Tien, et al. (författare)
  • Electron paramagnetic resonance and theoretical study of gallium vacancy in β-Ga2O3
  • 2020
  • Ingår i: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 117:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Unintentionally doped n-type beta -Ga2O3 becomes highly resistive after annealing at high temperatures in oxygen ambient. The annealing process also induces an electron paramagnetic resonance (EPR) center, labeled IR1, with an electron spin of S=1/2 and principal g-values of g(xx)=2.0160, g(yy)=2.0386, and g(zz)=2.0029 with the principal axis of g(zz) being 60 degrees from the [001](*) direction and g(yy) along the b-axis. A hyperfine (hf) structure due to the hf interaction between the electron spin and nuclear spins of two equivalent Ga atoms with a hf splitting of similar to 29G (for Ga-69) has been observed. The center can also be created by electron irradiation. Comparing the Ga hf constants determined by EPR with corresponding values calculated for different Ga vacancy-related defects, the IR1 defect is assigned to the double negative charge state of either the isolated Ga vacancy at the tetrahedral site (V-Ga(I)(2-)) or the V-Ga(I)-Ga-ib-V-Ga(I) complex.
  •  
33.
  • Nguyen, Son Tien, et al. (författare)
  • Energy levels and charge state control of the carbon antisite-vacancy defect in 4H-SiC
  • 2019
  • Ingår i: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 114:21
  • Tidskriftsartikel (refereegranskat)abstract
    • The carbon antisite-vacancy pair (CSiVC) in silicon carbide (SiC) has recently emerged as a promising defect for applications in quantum communication. In the positive charge state, CSiVC+ can be engineered to produce ultrabright single photon sources in the red spectral region, while in the neutral charge state, it has been predicted to emit light at telecom wavelengths and to have spin properties suitable for a quantum bit. In this electron paramagnetic resonance study using ultrapure compensated isotope-enriched 4H-(SiC)-Si-28, we determine the (+|0) level of CSiVC and show that the positive and neutral charge states of the defect can be optically controlled.
  •  
34.
  • Nguyen, Son Tien, et al. (författare)
  • Ligand hyperfine interactions at silicon vacancies in 4H-SiC
  • 2019
  • Ingår i: Journal of Physics. - : IOP PUBLISHING LTD. - 0953-8984 .- 1361-648X. ; 31:19
  • Tidskriftsartikel (refereegranskat)abstract
    • The negative silicon vacancy (V-Si(-)) in SiC has recently emerged as a promising defect for quantum communication and room-temperature quantum sensing. However, its electronic structure is still not well characterized. While the isolated Si vacancy is expected to give rise to only two paramagnetic centers corresponding to two inequivalent lattice sites in 4H-SiC, there have been five electron paramagnetic resonance (EPR) centers assigned to V-Si(-) in the past: the so-called isolated no-zero-field splitting (ZFS) V-Si(-) center and another four axial configurations with small ZFS: T-V1a, T-V2a, T-V1b, and T-V2b. Due to overlapping with Si-29 hyperfine (hf) structures in EPR spectra of natural 4H-SiC, hf parameters of T-V1a have not been determined. Using isotopically enriched 4H-(SiC)-Si-28, we overcome the problems of signal overlapping and observe hf parameters of nearest C neighbors for all three components of the S = 3/2 T-V1a and T-V2a centers. The obtained EPR data support the conclusion that only T-V1a and T-V2a are related to V-Si(-) and the two configurations of the so-called isolated no-ZFS V-Si(-) center, V-Si(-) (I) and V-Si(-) (II), are actually the central lines corresponding to the transition I-1/2 amp;lt;-amp;gt; I + 1/2 of the T-V2a and T-V1a centers, respectively.
  •  
35.
  • Niethammer, Matthias, et al. (författare)
  • Coherent electrical readout of defect spins in silicon carbide by photo-ionization at ambient conditions
  • 2019
  • Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 10
  • Tidskriftsartikel (refereegranskat)abstract
    • Quantum technology relies on proper hardware, enabling coherent quantum state control as well as efficient quantum state readout. In this regard, wide-bandgap semiconductors are an emerging material platform with scalable wafer fabrication methods, hosting several promising spin-active point defects. Conventional readout protocols for defect spins rely on fluorescence detection and are limited by a low photon collection efficiency. Here, we demonstrate a photo-electrical detection technique for electron spins of silicon vacancy ensembles in the 4H polytype of silicon carbide (SiC). Further, we show coherent spin state control, proving that this electrical readout technique enables detection of coherent spin motion. Our readout works at ambient conditions, while other electrical readout approaches are often limited to low temperatures or high magnetic fields. Considering the excellent maturity of SiC electronics with the outstanding coherence properties of SiC defects, the approach presented here holds promises for scalability of future SiC quantum devices.
  •  
36.
  • Niethammer, Matthias, et al. (författare)
  • Vector Magnetometry Using Silicon Vacancies in 4H-SiC Under Ambient Conditions
  • 2016
  • Ingår i: PHYSICAL REVIEW APPLIED. - : AMER PHYSICAL SOC. - 2331-7019. ; 6:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Point defects in solids promise precise measurements of various quantities. Especially magnetic field sensing using the spin of point defects has been of great interest recently. When optical readout of spin states is used, point defects achieve optical magnetic imaging with high spatial resolution at ambient conditions. Here, we demonstrate that genuine optical vector magnetometry can be realized using the silicon vacancy in SiC, which has an uncommon S = 3/2 spin. To this end, we develop and experimentally test sensing protocols based on a reference field approach combined with multifrequency spin excitation. Our work suggests that the silicon vacancy in an industry-friendly platform, SiC, has the potential for various magnetometry applications under ambient conditions.
  •  
37.
  • Ohshima, Kay I., et al. (författare)
  • Antarctic BottomWater production by intense sea-ice formation in the Cape Darnley polynya
  • 2013
  • Ingår i: Nature Geoscience. - 1752-0894 .- 1752-0908. ; 6:3, s. 235-240
  • Tidskriftsartikel (refereegranskat)abstract
    • The formation of Antarctic Bottom Water-the cold, dense water that occupies the abyssal layer of the global ocean-is a key process in global ocean circulation. This water mass is formed as dense shelf water sinks to depth. Three regions around Antarctica where this process takes place have been previously documented. The presence of another source has been identified in hydrographic and tracer data, although the site of formation is not well constrained. Here we document the formation of dense shelf water in the Cape Darnley polynya (65 degrees -69 degrees E) and its subsequent transformation into bottom water using data from moorings and instrumented elephant seals (Mirounga leonina). Unlike the previously identified sources of Antarctic Bottom Water, which require the presence of an ice shelf or a large storage volume, bottom water production at the Cape Darnley polynya is driven primarily by the flux of salt released by sea-ice formation. We estimate that about 0.3-0.7 x 10(6) m(3) s(-1) of dense shelf water produced by the Cape Darnley polynya is transformed into Antarctic BottomWater. The transformation of this water mass, which we term Cape Darnley BottomWater, accounts for 6-13% of the circumpolar total.
  •  
38.
  • Radulaski, Marina, et al. (författare)
  • Scalable Quantum Photonics with Single Color Centers in Silicon Carbide
  • 2017
  • Ingår i: Nano letters (Print). - : AMER CHEMICAL SOC. - 1530-6984 .- 1530-6992. ; 17:3, s. 1782-1786
  • Tidskriftsartikel (refereegranskat)abstract
    • Silicon carbide is a promising platform for single photon sources, quantum bits (qubits), and nanoscale sensors based on individual color centers. Toward this goal, we develop a scalable array of nanopillars incorporating single silicon vacancy centers in 4H-SiC, readily available for efficient interfacing with free-space objective and lensed-fibers. A commercially obtained substrate is irradiated with 2 MeV electron beams to create vacancies. Subsequent lithographic process forms 800 nm tall nanopillars with 400-1400 nm diameters. We obtain high collection efficiency of up to 22 kcounts/s optical saturation rates from a single silicon vacancy center while preserving the single photon emission and the optically induced electron-spin polarization properties. Our study demonstrates silicon carbide as a readily available platform for scalable quantum phtonics architecture relying on single photon sources and qubits.
  •  
39.
  • Radulaski, Marina, et al. (författare)
  • Scalable Quantum Photonics with Single Color Centers in Silicon Carbide
  • 2017
  • Ingår i: 2017 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO). - : IEEE. - 9781943580279
  • Konferensbidrag (refereegranskat)abstract
    • We develop a scalable array of 4H-SiC nanopillars incorporating single silicon vacancy centers, readily available to serve as efficient single photon sources or quantum bits interfaced with free-space or lensed-fiber optics.
  •  
40.
  • Shafizadeh, Danial, et al. (författare)
  • Selection rules in the excitation of the divacancy and the nitrogen-vacancy pair in 4H- and 6H-SiC
  • 2024
  • Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 109:23
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, we address selection rules with respect to the polarization of the optical excitation of two color centers in 4 H -SiC and 6 H -SiC with potential for applications in quantum technology, the divacancy and the nitrogen -vacancy pair. We show that the photoluminescence of the axial configurations of higher symmetry ( C 3 v ) than the basal ones ( C 1 h ) can be canceled using any excitation (resonant or nonresonant) with polarization parallel to the crystal axis ( E L || c ). The polarization selection rules are determined using group -theoretical analysis and simple physical arguments showing that phonon -assisted absorption with E L || c is prohibited despite being formally allowed by group theory. A comparison with the selection rules for the silicon vacancy, another defect with C 3 v symmetry, is also carried out. Using the selection rules, we demonstrate selective excitation of only one basal divacancy configuration in 4 H -SiC, the PL3 line, and discuss the higher contrast and increased Debye-Waller factor in the selectively excited spectrum.
  •  
41.
  • Silvano, Alessandro, et al. (författare)
  • Observing Antarctic Bottom Water in the Southern Ocean
  • 2023
  • Ingår i: Frontiers in Marine Science. - 2296-7745. ; 10
  • Forskningsöversikt (refereegranskat)abstract
    • Dense, cold waters formed on Antarctic continental shelves descend along the Antarctic continental margin, where they mix with other Southern Ocean waters to form Antarctic Bottom Water (AABW). AABW then spreads into the deepest parts of all major ocean basins, isolating heat and carbon from the atmosphere for centuries. Despite AABW's key role in regulating Earth's climate on long time scales and in recording Southern Ocean conditions, AABW remains poorly observed. This lack of observational data is mostly due to two factors. First, AABW originates on the Antarctic continental shelf and slope where in situ measurements are limited and ocean observations by satellites are hampered by persistent sea ice cover and long periods of darkness in winter. Second, north of the Antarctic continental slope, AABW is found below approximately 2 km depth, where in situ observations are also scarce and satellites cannot provide direct measurements. Here, we review progress made during the past decades in observing AABW. We describe 1) long-term monitoring obtained by moorings, by ship-based surveys, and beneath ice shelves through bore holes; 2) the recent development of autonomous observing tools in coastal Antarctic and deep ocean systems; and 3) alternative approaches including data assimilation models and satellite-derived proxies. The variety of approaches is beginning to transform our understanding of AABW, including its formation processes, temporal variability, and contribution to the lower limb of the global ocean meridional overturning circulation. In particular, these observations highlight the key role played by winds, sea ice, and the Antarctic Ice Sheet in AABW-related processes. We conclude by discussing future avenues for observing and understanding AABW, impressing the need for a sustained and coordinated observing system.
  •  
42.
  • Suvanam, Sethu Saveda, et al. (författare)
  • High Gamma Ray Tolerance for 4H-SiC Bipolar Circuits
  • 2016
  • Ingår i: IEEE Transactions on Nuclear Science. - : IEEE Press. - 0018-9499 .- 1558-1578.
  • Tidskriftsartikel (refereegranskat)abstract
    • A high gamma radiation hardness of 4H-SiC circuits is performed. The OR NOR circuits are based on emitter coupled logic (ECL), using integrated bipolar NPN transistors. Gain degradation in individual bipolar junction transistors (BJT) is minimal up to a dose of 38 Mrad (SiO2), but for the dose of 332 Mrad (SiO2) a degradation of 52% is observed. The SiC BJTs show higher radiation hardness than existing Si-technology and high stability under temperature stress. It is proposed that the oxide charge-dominated recombination is the key base current recombination mechanism contributing to gain degradation. An improvement in the gain is seen after annealing at 400 °C for 1800 s due to the possible annealing of some of the oxide defects contributing to the oxide charge.
  •  
43.
  • Tan-No, Koichi, et al. (författare)
  • Antinociceptive effect produced by intracerebroventricularly administered dynorphin A is potentiated by p-hydroxymercuribenzoate or phosphoramidon in the mouse formalin test
  • 2001
  • Ingår i: Brain Research. - 0006-8993 .- 1872-6240. ; 891:1-2, s. 274-280
  • Tidskriftsartikel (refereegranskat)abstract
    • The antinociceptive effects of intracerebroventricularly (i.c.v.) administered dynorphin A, an endogenous agonist for kappa-opioid receptors, in combination with various protease inhibitors were examined using the mouse formalin test in order to clarify the nature of the proteases involved in the degradation of dynorphin A in the mouse brain. When administered i.c.v. 15 min before the injection of 2% formalin solution into the dorsal surface of a hindpaw, 1-4 nmol dynorphin A produced a dose-dependent reduction of the nociceptive behavioral response consisting of licking and biting of the injected paw during both the first (0-5 min) and second (10-30 min) phases. When co-administered with p-hydroxymercuribenzoate (PHMB), a cysteine protease inhibitor, dynorphin A at the subthreshold dose of 0.5 nmol significantly produced an antinociceptive effect during the second phase. This effect was significantly antagonized by nor-binaltorphimine, a selective kappa-opioid receptor antagonist, but not by naltrindole, a selective delta-opioid receptor antagonist. At the same dose of 0.5 nmol, dynorphin A in combination with phosphoramidon, an endopeptidase 24.11 inhibitor, produced a significant antinociceptive effect during both phases. The antinociceptive effect was significantly antagonized by naltrindole, but not by nor-binaltorphimine. Phenylmethanesulfonyl fluoride (PMSF), a serine protease inhibitor, bestatin, a general aminopeptidase inhibitor, and captopril, an angiotensin-converting enzyme inhibitor, were all inactive. The degradation of dynorphin A by mouse brain extracts in vitro was significantly inhibited only by the cysteine protease inhibitors PHMB and N-ethylmaleimide, but not by PMSF, phosphoramidon, bestatin or captopril. The present results indicate that cysteine proteases as well as endopeptidase 24.11 are involved in two steps in the degradation of dynorphin A in the mouse brain, and that phosphoramidon inhibits the degradation of intermediary delta-opioid receptor active fragments enkephalins which are formed from dynorphin A.
  •  
44.
  • Udvarhelyi, Peter, et al. (författare)
  • Vibronic States and Their Effect on the Temperature and Strain Dependence of Silicon-Vacancy Qubits in 4H-SiC
  • 2020
  • Ingår i: Physical Review Applied. - : AMER PHYSICAL SOC. - 2331-7019. ; 13:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Silicon-vacancy qubits in silicon carbide (SiC) are emerging tools in quantum-technology applications due to their excellent optical and spin properties. In this paper, we explore the effect of temperature and strain on these properties by focusing on the two silicon-vacancy qubits, V1 and V2, in 4H-SiC. We apply density-functional theory beyond the Born-Oppenheimer approximation to describe the temperature-dependent mixing of electronic excited states assisted by phonons. We obtain a polaronic gap of around 5 and 22 meV for the V1 and V2 centers, respectively, which results in a significant difference in the temperature-dependent dephasing and zero-field splitting of the excited states, which explains recent experimental findings. We also compute how crystal deformations affect the zero-phonon line of these emitters. Our predictions are important ingredients in any quantum applications of these qubits sensitive to these effects.
  •  
45.
  • White, Alexander D., et al. (författare)
  • Static and Dynamic Stark Tuning of the Silicon Vacancy in Silicon Carbide
  • 2020
  • Ingår i: 2020 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO). - : IEEE. - 9781943580767
  • Konferensbidrag (refereegranskat)abstract
    • We present the DC Stark tuning of single Silicon Vacancies in SiC. We demonstrate static tuning across 200 GHz, exceeding the inhomogenous broadening, and dynamic tuning on timescales shorter than the optical decay rate. (C) 2020 The Author(s)
  •  
46.
  • Widmann, Matthias, et al. (författare)
  • Bright single photon sources in lateral silicon carbide light emitting diodes
  • 2018
  • Ingår i: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 112:23
  • Tidskriftsartikel (refereegranskat)abstract
    • Single-photon emitting devices have been identified as an important building block for applications in quantum information and quantum communication. They allow us to transduce and collect quantum information over a long distance via photons as so-called flying qubits. In addition, substrates like silicon carbide provide an excellent material platform for electronic devices. In this work, we combine these two features and show that one can drive single photon emitters within a silicon carbide p-i-n-diode. To achieve this, we specifically designed a lateral oriented diode. We find a variety of new color centers emitting non-classical lights in the visible and near-infrared range. One type of emitter can be electrically excited, demonstrating that silicon carbide can act as an ideal platform for electrically controllable single photon sources. Published by AIP Publishing.
  •  
47.
  • Widmann, Matthias, et al. (författare)
  • Coherent control of single spins in silicon carbide at room temperature
  • 2015
  • Ingår i: Nature Materials. - : Nature Publishing Group. - 1476-1122 .- 1476-4660. ; 14:2, s. 164-168
  • Tidskriftsartikel (refereegranskat)abstract
    • Spins in solids are cornerstone elements of quantum spintronics(1). Leading contenders such as defects in diamond(2-5) or individual phosphorus dopants in silicon(6) have shown spectacular progress, but either lack established nanotechnology or an efficient spin/photon interface. Silicon carbide (SiC) combines the strength of both systems(5):it has a large bandgap with deep defects(7-9) and benefits from mature fabrication techniques(10-12). Here, we report the characterization of photoluminescence and optical spin polarization from single silicon vacancies in SiC, and demonstrate that single spins can be addressed at room temperature. We show coherent control of a single defect spin and find long spin coherence times under ambient conditions. Our study provides evidence that SiC is a promising system for atomic-scale spintronics and quantum technology.
  •  
48.
  • Widmann, Matthias, et al. (författare)
  • Electrical Charge State Manipulation of Single Silicon Vacancies in a Silicon Carbide Quantum Optoelectronic Device
  • 2019
  • Ingår i: Nano letters (Print). - : AMER CHEMICAL SOC. - 1530-6984 .- 1530-6992. ; 19:10, s. 7173-7180
  • Tidskriftsartikel (refereegranskat)abstract
    • Color centers with long-lived spins are established platforms for quantum sensing and quantum information applications. Color centers exist in different charge states, each of them with distinct optical and spin properties. Application to quantum technology requires the capability to access and stabilize charge states for each specific task. Here, we investigate charge state manipulation of individual silicon vacancies in silicon carbide, a system which has recently shown a unique combination of long spin coherence time and ultrastable spin-selective optical transitions. In particular, we demonstrate charge state switching through the bias applied to the color center in an integrated silicon carbide optoelectronic device. We show that the electronic environment defined by the doping profile and the distribution of other defects in the device plays a key role for charge state control. Our experimental results and numerical modeling evidence that control of these complex interactions can, under certain conditions, enhance the photon emission rate. These findings open the way for deterministic control over the charge state of spin-active color centers for quantum technology and provide novel techniques for monitoring doping profiles and voltage sensing in microscopic devices.
  •  
49.
  • Zwier, Olger V, et al. (författare)
  • Electromagnetically induced transparency in inhomogeneously broadened divacancy defect ensembles in SiC
  • 2022
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 131:9
  • Tidskriftsartikel (refereegranskat)abstract
    • Electromagnetically induced transparency (EIT) is a phenomenon that can provide strong and robust interfacing between optical signals and quantum coherence of electronic spins. In its archetypical form, mainly explored with atomic media, it uses a (near-)homogeneous ensemble of three-level systems, in which two low-energy spin-1/2 levels are coupled to a common optically excited state. We investigate the implementation of EIT with c-axis divacancy color centers in silicon carbide. While this material has attractive properties for quantum device technologies with near-IR optics, implementing EIT is complicated by the inhomogeneous broadening of the optical transitions throughout the ensemble and the presence of multiple ground-state levels. These may lead to darkening of the ensemble upon resonant optical excitation. Here, we show that EIT can be established with high visibility also in this material platform upon careful design of the measurement geometry. Comparison of our experimental results with a model based on the Lindblad equations indicates that we can create coherences between different sets of two levels all-optically in these systems, with potential impact for RF-free quantum sensing applications. Our work provides an understanding of EIT in multi-level systems with significant inhomogeneities, and our considerations are valid for a wide array of defects in semiconductors. Published under an exclusive license by AIP Publishing.
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