| 1. |
- Asadzadeh, Mohammad Zhian, et al.
(författare)
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Response modeling of single SnO2 nanowire gas sensors
- 2019
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 295, s. 22-29
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Tidskriftsartikel (refereegranskat)abstract
- The response of single SnO2 nanowire gas sensors with different diameters between 20 and 140 nm are evaluated by calculating the nanowire conductivity as a function of the surface charge density. The procedure involves the numerical solution of the Poisson-Boltzmann equation for the electrostatic potential in cylindrical geometry in order to model the depletion region and band bending at the SnO2 nanowire surface. In the model we take into account varying surface charge densities sigma and bulk electron concentrations n(0) to calculate the electrical conductivity. Considering the fact that the surface charge density depends on the nanowire surface interactions with ambient gas, the model allows us to simulate the sensor response when the nanowire is employed as gas sensing component. We report a saturation in depletion length lambda versus surface charge density s which is the principal reason for limiting the sensor responses. The results also show that the conductivity is decreasing by increasing surface charge density, the smaller the nanowire diameter the steeper the decrease. As a result the nanowire response is proportional to 1/d where d is the nanowire diameter. Furthermore, we argue about the validity of the modeling results and their relevance to experimental findings on SnO2 nanowire based gas sensors reported in literature.
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| 2. |
- Ay, Hakan, et al.
(författare)
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Pathogenic Ischemic Stroke Phenotypes in the NINDS-Stroke Genetics Network
- 2014
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Ingår i: Stroke. - 0039-2499. ; 45:12, s. 3589-3596
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: NINDS (National Institute of Neurological Disorders and Stroke)-SiGN (Stroke Genetics Network) is an international consortium of ischemic stroke studies that aims to generate high-quality phenotype data to identify the genetic basis of pathogenic stroke subtypes. This analysis characterizes the etiopathogenetic basis of ischemic stroke and reliability of stroke classification in the consortium. METHODS: Fifty-two trained and certified adjudicators determined both phenotypic (abnormal test findings categorized in major pathogenic groups without weighting toward the most likely cause) and causative ischemic stroke subtypes in 16954 subjects with imaging-confirmed ischemic stroke from 12 US studies and 11 studies from 8 European countries using the web-based Causative Classification of Stroke System. Classification reliability was assessed with blinded readjudication of 1509 randomly selected cases. RESULTS: The distribution of pathogenic categories varied by study, age, sex, and race (P<0.001 for each). Overall, only 40% to 54% of cases with a given major ischemic stroke pathogenesis (phenotypic subtype) were classified into the same final causative category with high confidence. There was good agreement for both causative (κ 0.72; 95% confidence interval, 0.69-0.75) and phenotypic classifications (κ 0.73; 95% confidence interval, 0.70-0.75). CONCLUSIONS: This study demonstrates that pathogenic subtypes can be determined with good reliability in studies that include investigators with different expertise and background, institutions with different stroke evaluation protocols and geographic location, and patient populations with different epidemiological characteristics. The discordance between phenotypic and causative stroke subtypes highlights the fact that the presence of an abnormality in a patient with stroke does not necessarily mean that it is the cause of stroke.
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| 3. |
- Becher, Christoph, et al.
(författare)
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2023 roadmap for materials for quantum technologies
- 2023
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Ingår i: Materials for Quantum Technology. - : IOP Publishing. - 2633-4356. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Quantum technologies are poised to move the foundational principles of quantum physics to the forefront of applications. This roadmap identifies some of the key challenges and provides insights on material innovations underlying a range of exciting quantum technology frontiers. Over the past decades, hardware platforms enabling different quantum technologies have reached varying levels of maturity. This has allowed for first proof-of-principle demonstrations of quantum supremacy, for example quantum computers surpassing their classical counterparts, quantum communication with reliable security guaranteed by laws of quantum mechanics, and quantum sensors uniting the advantages of high sensitivity, high spatial resolution, and small footprints. In all cases, however, advancing these technologies to the next level of applications in relevant environments requires further development and innovations in the underlying materials. From a wealth of hardware platforms, we select representative and promising material systems in currently investigated quantum technologies. These include both the inherent quantum bit systems and materials playing supportive or enabling roles, and cover trapped ions, neutral atom arrays, rare earth ion systems, donors in silicon, color centers and defects in wide-band gap materials, two-dimensional materials and superconducting materials for single-photon detectors. Advancing these materials frontiers will require innovations from a diverse community of scientific expertise, and hence this roadmap will be of interest to a broad spectrum of disciplines.
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| 4. |
- Bienfang, J. C., et al.
(författare)
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Materials, devices, and systems for high-speed single-photon counting
- 2022
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Ingår i: MRS bulletin. - : Springer Nature. - 0883-7694 .- 1938-1425. ; 47:5, s. 494-501
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Tidskriftsartikel (refereegranskat)abstract
- Optical communications and high-speed optoelectronics are enabling technologies for modern information networks. Driven by the need for improved bandwidth, high efficiency, and low noise, advances over the last decades have led to high-performance photodetectors operating at the quantum limit. In particular, single-photon avalanche diodes (SPADs) and superconducting nanowire single-photon detectors (SNSPDs) provide excellent performance in terms of high detection efficiency and low noise. In this article, we highlight materials challenges in these detectors and review recent progress on devices, and systems for high-count-rate single-photon counting with SPADs and SNSPDs. Device configurations specifically designed for high-speed optoelectronics are discussed, including active detector readout schemes. Advantages and tradeoffs of the different device technologies are summarized and compared, providing an outlook on future prospects for performance optimization and emerging applications.
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| 5. |
- Branny, Artur, et al.
(författare)
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X-Ray Induced Secondary Particle Counting With Thin NbTiN Nanowire Superconducting Detector
- 2021
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Ingår i: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 31:4
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Tidskriftsartikel (refereegranskat)abstract
- We characterized the performance of abiased superconducting nanowire to detect X-ray photons. The device, made of a 10 nm thin NbTiN film and fabricated on a dielectric substrate (SiO2, Nb3O5) detected 1000 times larger signal than anticipated from direct X-ray absorption. We attributed this effect to X-ray induced generation of secondary particles in the substrate. The enhancement corresponds to an increase in the flux by the factor of 3.6, relative to a state-of-the-art commercial X-ray silicon drift detector. The detector exhibited 8.25 ns temporal recovery time and 82 ps timing resolution, measured using optical photons. Our results emphasize the importance of the substrate in superconducting X-ray single photon detectors.
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| 6. |
- Chang, Jin, et al.
(författare)
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Efficient mid-infrared single-photon detection using superconducting NbTiN nanowires with high time resolution in a Gifford-McMahon cryocooler
- 2022
-
Ingår i: Photonics Research. - : Optica Publishing Group. - 2327-9125. ; 10:4, s. 1063-1070
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Tidskriftsartikel (refereegranskat)abstract
- Shortly after their inception, superconducting nanowire single-photon detectors (SNSPDs) became the leading quantum light detection technology. With the capability of detecting single-photons with near-unity efficiency, high time resolution, low dark count rate, and fast recovery time, SNSPDs outperform conventional single-photon detection techniques. However, detecting lower energy single photons (<0.8 eV) with high efficiency and low timing jitter has remained a challenge. To achieve unity internal efficiency at mid-infrared wavelengths, previous works used amorphous superconducting materials with low energy gaps at the expense of reduced time resolution (close to a nanosecond), and by operating them in complex milliKelvin (mK) dilution refrigerators. In this work, we provide an alternative approach with SNSPDs fabricated from 5 to 9.5 nm thick NbTiN superconducting films and devices operated in conventional Gifford-McMahon cryocoolers. By optimizing the superconducting film deposition process, film thickness, and nanowire design, our fiber-coupled devices achieved >70% system detection efficiency (SDE) at 2 mu m and sub-15 ps timing jitter. Furthermore, detectors from the same batch demonstrated unity internal detection efficiency at 3 mu m and 80% internal efficiency at 4 mu m, paving the road for an efficient mid-infrared single-photon detection technology with unparalleled time resolution and without mK cooling requirements. We also systematically studied the dark count rates (DCRs) of our detectors coupled to different types of mid-infrared optical fibers and blackbody radiation filters. This offers insight into the trade-off between bandwidth and DCRs for mid-infrared SNSPDs. To conclude, this paper significantly extends the working wavelength range for SNSPDs made from polycrystalline NbTiN to 1.5-4 mu m, and we expect quantum optics experiments and applications in the mid-infrared range to benefit from this far-reaching technology. Published by Chinese Laser Press under the terms of the Creative Commons Attribution 4.0 License.
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| 7. |
- Chen, Pei Jung, et al.
(författare)
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Visualizing Local Superconductivity of NbTiN Nanowires to Probe Inhomogeneity in Single-Photon Detectors
- 2024
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Ingår i: ACS Applied Optical Materials. - : American Chemical Society (ACS). - 2771-9855. ; 2:1, s. 68-75
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Tidskriftsartikel (refereegranskat)abstract
- NbTiN has a high critical temperature (Tc) of up to 17 K, making it a great candidate for superconducting nanowire single-photon detectors (SNSPDs) and other applications requiring a bias current close to the depairing current. However, superconducting inhomogeneities are often observed in superconducting thin films, and superconducting inhomogeneities can influence the vortex nucleation barrier and furthermore affect the critical current Ic of a superconducting wire. Superconducting inhomogeneities can also result in stochastic variations in the critical current between identical devices, and therefore, it is crucial to have a detailed understanding of inhomogeneities in SNSPDs in order to improve device efficiency. In this study, we utilized scanning tunneling microscopy/spectroscopy (STM/STS) to investigate the inhomogeneity of superconducting properties in meandered NbTiN nanowires, which are commonly used in SNSPDs. Our findings show that variations in the superconducting gap are strongly correlated with the film thickness. By using time-dependent Ginzburg-Landau simulations and statistical modeling, we explored the implications of the reduction in the critical current and its sample-to-sample variations. Our study suggests that the thickness of NbTiN plays a critical role in achieving homogeneity in superconducting properties.
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| 8. |
- Cherchi, Matteo, et al.
(författare)
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A path towards attojoule cryogenic communication
- 2022
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Ingår i: 2022 European Conference on Optical Communication, ECOC 2022. - : Institute of Electrical and Electronics Engineers Inc..
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Konferensbidrag (refereegranskat)abstract
- Photonic integration technologies are key to scale-up superconducting quantum computers. Here, we identify suitable classical optical links to control and read out the qubits in cryostats and resolve the power dissipation issue of superconducting computing platforms. Recent results and future solutions are shown.
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| 9. |
- Datta, Abheek, et al.
(författare)
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Single Nanoparticle Activities in Ensemble : A Study on Pd Cluster Nanoportals for Electrochemical Oxygen Evolution Reaction
- 2019
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 123:43, s. 26124-26135
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Tidskriftsartikel (refereegranskat)abstract
- Comprehensive understanding of the electrochemical activity of single nanoparticles (NPs) is in critical need for opening new avenues in the broad field of electrochemistry. Published reports on single-NP electrocatalysts typically include complicated and difficult methods of synthesis and characterization; moreover, these methods usually fail to provide a reliable way to measure the activities of individual NPs within larger ensembles of particles, i.e., in real-life nanocatalyst systems. In the present work, we synthesized from the gas phase Pd NPs that act as nanoportals for electron transfer within surface-oxidized Mg thin films. The physical synthesis method provided excellent control over the deposition density and, hence, enabled the design of a system where each individual open nanoportal forms an independent active single-NP electrode (SNPE). Being uncoupled from one another, these SNPEs contribute separately toward the total electrocatalytic activity while simultaneously providing a measure of their average, individual activities. We were thus able to fabricate a stable, steady-state electrode for the electrochemical oxygen evolution reaction (OER) and to study the activity and stability of the SNPEs over a period of 20 days; the former depended on the size of the NPs, while the latter depended on the SNPEs' resistance to aerial oxidation. The remarkable stability of the ensemble catalysts under OER conditions proves that this concept can be used for further studies on the activities of different single NPs in numerous real-life systems.
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| 10. |
- DeLange, Jacob, et al.
(författare)
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Highly-excited Rydberg excitons in synthetic thin-film cuprous oxide
- 2023
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 13:1, s. 16881-
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Tidskriftsartikel (refereegranskat)abstract
- Cuprous oxide ([Formula: see text]) has recently emerged as a promising material in solid-state quantum technology, specifically for its excitonic Rydberg states characterized by large principal quantum numbers (n). The significant wavefunction size of these highly-excited states (proportional to [Formula: see text]) enables strong long-range dipole-dipole (proportional to [Formula: see text]) and van der Waals interactions (proportional to [Formula: see text]). Currently, the highest-lying Rydberg states are found in naturally occurring [Formula: see text]. However, for technological applications, the ability to grow high-quality synthetic samples is essential. The fabrication of thin-film [Formula: see text] samples is of particular interest as they hold potential for observing extreme single-photon nonlinearities through the Rydberg blockade. Nevertheless, due to the susceptibility of high-lying states to charged impurities, growing synthetic samples of sufficient quality poses a substantial challenge. This study successfully demonstrates the CMOS-compatible synthesis of a [Formula: see text] thin film on a transparent substrate that showcases Rydberg excitons up to [Formula: see text] which is readily suitable for photonic device fabrications. These findings mark a significant advancement towards the realization of scalable and on-chip integrable Rydberg quantum technologies.
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| 11. |
- Elshaari, Ali W., et al.
(författare)
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Deterministic Integration of hBN Emitter in Silicon Nitride Photonic Waveguide
- 2021
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Ingår i: Advanced Quantum Technologies. - : Wiley. - 2511-9044. ; 4:6, s. 2100032-
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid integration provides an important avenue for incorporating atom-like solid-state single-photon emitters into photonic platforms that possess no optically-active transitions. Hexagonal boron nitride (hBN) is particularly interesting quantum emitter for hybrid integration, as it provides a route for room-temperature quantum photonic technologies, coupled with its robustness and straightforward activation. Despite the recent progress of integrating hBN emitters in photonic waveguides, a deterministic, site-controlled process remains elusive. Here, the integration of selected hBN emitter in silicon nitride waveguide is demonstrated. A small misalignment angle of 4° is shown between the emission-dipole orientation and the waveguide propagation direction. The integrated emitter maintains high single-photon purity despite subsequent encapsulation and nanofabrication steps, delivering quantum light with zero delay second order correlation function (Formula presented.). The results provide an important step toward deterministic, large scale, quantum photonic circuits at room temperature using atom-like single-photon emitters.
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| 12. |
- Elshaari, Ali W., et al.
(författare)
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Dispersion engineering of superconducting waveguides for multi-pixel integration of single-photon detectors
- 2020
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Ingår i: APL Photonics. - : American Institute of Physics (AIP). - 2378-0967. ; 5:11
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Tidskriftsartikel (refereegranskat)abstract
- We use dispersion engineering to control the signal propagation speed in the feed lines of superconducting single-photon detectors. Using this technique, we demonstrate time-division-multiplexing of two-pixel detectors connected with a slow-RF transmission line, all realized using planar geometry requiring a single lithographic step. Through studying the arrival time of detection events in each pixel vs the fabricated slow-RF coplanar waveguide length, we extract a delay of 1.7 ps per 1 mu m of propagation, corresponding to detection signal speeds of similar to 0.0019c. Our results open an important avenue to explore the rich ideas of dispersion engineering and metamaterials for superconducting detector applications.
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| 13. |
- Errando-Herranz, Carlos, et al.
(författare)
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Transfer-Printed Single-Photon Detectors on Arbitrary Photonic Substrates
- 2023
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Ingår i: 2023 Conference on Lasers and Electro-Optics, CLEO 2023. - : Institute of Electrical and Electronics Engineers Inc..
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Konferensbidrag (refereegranskat)abstract
- We demonstrate the integration of superconducting single-photon detectors onto arbitrary photonic substrates via transfer printing. Using this method, we show single-photon detection in a lithium niobate on insulator photonic circuit.
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| 14. |
- Esmaeil Zadeh, Iman, et al.
(författare)
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Superconducting nanowire single-photon detectors : A perspective on evolution, state-of-the-art, future developments, and applications
- 2021
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 118:19
-
Tidskriftsartikel (refereegranskat)abstract
- Two decades after their demonstration, superconducting nanowire single-photon detectors (SNSPDs) have become indispensable tools for quantum photonics as well as for many other photon-starved applications. This invention has not only led to a burgeoning academic field with a wide range of applications but also triggered industrial efforts. Current state-of-the-art SNSPDs combine near-unity detection efficiency over a wide spectral range, low dark counts, short dead times, and picosecond time resolution. The present perspective discusses important milestones and progress of SNSPDs research, emerging applications, and future challenges and gives an outlook on technological developments required to bring SNSPDs to the next level: a photon-counting, fast time-tagging imaging, and multi-pixel technology that is also compatible with quantum photonic integrated circuits.
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| 15. |
- Feng, Yifan, et al.
(författare)
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Fractal Superconducting Nanowire Single-Photon Detectors and Their Applications in Imaging
- 2022
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Ingår i: Proceedings of the 2022 Conference on Lasers and Electro-Optics Pacific Rim, CLEO/PR 2022. - : Optica Publishing Group.
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Konferensbidrag (refereegranskat)abstract
- We present our research on fractal superconducting nanowire single-photon detectors and their applications in light detection and ranging (LiDAR), full-Stokes polarimetric imaging, and non-line-of-sight imaging.
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| 16. |
- Feng, Yifan, et al.
(författare)
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Fractal Superconducting Nanowire Single-Photon Detectors and Their Applications in Imaging
- 2022
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Ingår i: 2022 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2022 - Proceedings. - : Institute of Electrical and Electronics Engineers Inc..
-
Konferensbidrag (refereegranskat)abstract
- We present our research on fractal superconducting nanowire single-photon detectors and their applications in light detection and ranging (LiDAR), full-Stokes polarimetric imaging, and non-line-of-sight imaging.
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| 17. |
- Gao, Jun, et al.
(författare)
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Observation of Anderson phase in a topological photonic circuit
- 2022
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Ingår i: Physical Review Research. - : American Physical Society (APS). - 2643-1564. ; 4:3
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Tidskriftsartikel (refereegranskat)abstract
- Disordered systems play a central role in condensed matter physics, quantum transport, and topological photonics. It is commonly believed that a topological nontrivial phase would turn into a trivial phase where the transport vanishes under the effect of Anderson localization. Recent studies predict a counterintuitive result, that adding disorder to the trivial band structure triggers the emergence of protected edge states, the so-called topological Anderson phase. Here, we experimentally observe such a topological Anderson phase in a CMOS-compatible nanophotonic circuit, which implements the Su-Schrieffer-Heeger (SSH) model with incommensurate disorder in the intercell coupling amplitudes. The existence of the Anderson phase is verified by the spectral method, based on the continuous detection of the nanoscale light dynamics at the edge. Our results demonstrate the inverse transition between distinct topological phases in the presence of disorder, as well as offering a single-shot measurement technique to study the light dynamics in nanophotonic systems.
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| 18. |
- Gao, Jun, et al.
(författare)
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Scalable Generation and Detection of on-Demand W States in Nanophotonic Circuits
- 2023
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 23:11, s. 5350-5357
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Tidskriftsartikel (refereegranskat)abstract
- Quantum physics phenomena,entanglement and coherence,are crucialfor quantum information protocols, but understanding these in systemswith more than two parts is challenging due to increasing complexity.The W state, a multipartite entangled state, is notable for its robustnessand benefits in quantum communication. Here, we generate eight-modeon-demand single-photon W states, using nanowire quantum dots anda silicon nitride photonic chip. We demonstrate a reliable and scalabletechnique for reconstructing the W state in photonic circuits usingFourier and real-space imaging, supported by the Gerchberg-Saxtonphase retrieval algorithm. Additionally, we utilize an entanglementwitness to distinguish between mixed and entangled states, therebyaffirming the entangled nature of our generated state. The study providesa new imaging approach of assessing multipartite entanglement in Wstates, paving the way for further progress in image processing andFourier-space analysis techniques for complex quantum systems.
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| 19. |
- Grammatikopoulos, Panagiotis, et al.
(författare)
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Gas-phase synthesis of nanoparticles : current application challenges and instrumentation development responses
- 2023
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 25:2, s. 897-912
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Tidskriftsartikel (refereegranskat)abstract
- Nanoparticles constitute fundamental building blocks required in several fields of application with current global importance. To fully exploit nanoparticle properties specifically determined by the size, shape, chemical composition and interfacial configuration, rigorous nanoparticle growth and deposition control is needed. Gas-phase synthesis, in particular magnetron-sputtering inert-gas condensation, provides unique opportunities to realise engineered nanoparticles optimised for the desired use case. Here, we provide an overview of recent nanoparticle growth experiments via this technique, how the latter can meet application-specific requirements, and what challenges might impede the wide-spread adoption for scalable industrial synthesis. More specifically, we discuss the timely topics of energy, catalysis, and sensing applications enabled by gas-phase synthesised nanoparticles, as well as recently emerging advances in neuromorphic devices for unconventional computing. Having identified the most relevant challenges and limiting factors, we outline how advances in nanoparticle source instrumentation and/or in situ diagnostics can address current shortcomings. Eventually we identify common trends and directions, giving our perspective on the most promising and impactful applications of gas-phase synthesised nanoparticles in the future.
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| 20. |
- Gyger, Samuel, 1991-
(författare)
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Integrated Photonics for Quantum Optics
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Quantum physics allows us a vision of Nature's forces that bind the world, all its seeds and sources. After decades of primarily scientific research, we've arrived at a stage in time where quantum technology can be applied to practical problems and add value outside the field. Four pillars of quantum technologies are commonly identified: quantum computing, quantum simulation, quantum communication, and quantum sensing. For example, quantum computers will allow us to model quantum systems beyond our current capabilities, and quantum communication allows us to protect information unconditionally based on physics. Quantum sensing will enable us to measure our reality beyond classical limits.Within all of these areas, optical photons play a unique role. In quantum computer implementations (e.g. photonic, trapped ion, or superconducting) photons can serve as a computational resource, for system read-out, or for linking distant hardware nodes. Quantum communication can only be realized via photons, utilizing the low-loss propagation of photons in optical fibers, on photonic devices as well as in free space. In quantum sensing and metrology, squeezed light can be used to go beyond the current limits of sensing methods. Therefore, the quantum technology field crucially relies on precise and efficient methods to generate, steer, manipulate and detect photons.This dissertation discusses work in integrated photonic circuits, self-assembled semiconductor quantum dot devices, and superconducting nanowire single--photon detectors.We integrate multiple materials on a silicon nitride platform, including Cu2O as a platform for solid-state Rydberg physics, WS2 to improve non-linear light-generation within Si3N4, and hBN as an excellent single-photon emitter.We demonstrate optically active quantum dots as single-photon emitters in the telecom C-band and their compatibility with commercial telecom equipment.We strain-control the fine-structure splitting of these devices, which is required for future quantum interference-based protocols.Finally, we study superconducting nanowire single-photon detectors (SNSPD) and combine them with photonic micro-electromechanical systems (MEMS), establishing a cryo-compatible, reconfigurable photonic platform.
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| 21. |
- Gyger, Samuel, et al.
(författare)
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Metropolitan single-photon distribution at 1550 nm for random number generation
- 2022
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 121:19, s. 194003-
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Tidskriftsartikel (refereegranskat)abstract
- Quantum communication networks will connect future generations of quantum processors, enable metrological applications, and provide security through quantum key distribution. We present a testbed that is part of the municipal fiber network in the greater Stockholm metropolitan area for quantum resource distribution through a 20 km long fiber based on semiconductor quantum dots emitting in the telecom C-band. We utilize the service to generate random numbers passing the NIST test suite SP800-22 at a subscriber 8 km outside of the city with a bit rate of 23.4 kbit/s.
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| 22. |
- Gyger, Samuel, et al.
(författare)
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Metropolitan Single-Photon Distribution at 1550 nm for Random Number Generation
- 2023
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Ingår i: 2023 Conference on Lasers and Electro-Optics, CLEO 2023. - : Institute of Electrical and Electronics Engineers Inc..
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Konferensbidrag (refereegranskat)abstract
- Quantum communication networks are used for QKD and metrological applications. We present research connecting two nodes ≈ 20 kilometers apart over the municipal fiber network using semiconductor quantum dots emitting at 1550 nm.
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| 23. |
- Gyger, Samuel, et al.
(författare)
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On-chip integration of reconfigurable quantum photonics with superconducting photodetectors
- 2021
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Ingår i: 2021 Conference on Lasers and Electro-Optics, CLEO 2021 - Proceedings. - : Institute of Electrical and Electronics Engineers Inc..
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Konferensbidrag (refereegranskat)abstract
- Scaling up quantum optics experiments requires on-chip reconfigurable quantum photonics, but their integration with detectors is a challenge. We show microelectrome-chanical reconfiguration of photonic circuits with on-chip superconducting single-photon detectors and demonstrate key applications.
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| 24. |
- Gyger, Samuel, et al.
(författare)
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Reconfigurable photonics with on-chip single-photon detectors
- 2021
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Integrated quantum photonics offers a promising path to scale up quantum optics experiments by miniaturizing and stabilizing complex laboratory setups. Central elements of quantum integrated photonics are quantum emitters, memories, detectors, and reconfigurable photonic circuits. In particular, integrated detectors not only offer optical readout but, when interfaced with reconfigurable circuits, allow feedback and adaptive control, crucial for deterministic quantum teleportation, training of neural networks, and stabilization of complex circuits. However, the heat generated by thermally reconfigurable photonics is incompatible with heat-sensitive superconducting single-photon detectors, and thus their on-chip co-integration remains elusive. Here we show low-power microelectromechanical reconfiguration of integrated photonic circuits interfaced with superconducting single-photon detectors on the same chip. We demonstrate three key functionalities for photonic quantum technologies: 28 dB high-extinction routing of classical and quantum light, 90 dB high-dynamic range single-photon detection, and stabilization of optical excitation over 12 dB power variation. Our platform enables heat-load free reconfigurable linear optics and adaptive control, critical for quantum state preparation and quantum logic in large-scale quantum photonics applications. Integrated photonics are promising to scale up quantum optics. Here the authors combine low-power microelectromechanical control and superconducting single-photon detectors on the same chip and demonstrate routing, high-dynamic-range detection, and power stabilization.
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| 25. |
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| 26. |
- Hu, Nan, et al.
(författare)
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Full-Stokes polarimetric measurements and imaging using a fractal superconducting nanowire single-photon detector
- 2022
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Ingår i: Optica. - : Optica Publishing Group. - 2334-2536. ; 9:4, s. 346-351
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Tidskriftsartikel (refereegranskat)abstract
- Measuring the states of polarization (SoP) of light is fundamentally important for applications ranging from communication, sensing, spectroscopy, imaging, to navigation. Superconducting nanowire single-photon detectors (SNSPDs) are ideal detectors of choice for faint-light detection and measurements, but SNSPDs themselves cannot resolve the SoP of photons. Here, based on a fractal SNSPD, we demonstrate a full-Stokes polarimetric measurement system that can measure arbitrary SoP of faint light. The measured SoPs are in excellent agreement with those of a state-of-the-art commercial polarimeter, but the sensitivity of our system reaches -86.6 dBm, which is 26.6 dB better than that of the commercial counterpart. As a direct application, we further demonstrate remote polarimetric imaging (i.e., polarimetric LiDAR) with a complete set of polarimetric contrast.
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| 27. |
- Hu, Nan, et al.
(författare)
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Photon-Counting LIDAR Based on a Fractal SNSPD
- 2021
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Ingår i: 2021 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXPOSITION (OFC). - : IEEE.
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Konferensbidrag (refereegranskat)abstract
- We report on a photon-counting LIDAR system based on a polarization-insensitive fractal SNSPD with high detection efficiency and high timing resolution, and showcase depth imaging of an object at 1560 nm with millimeter depth resolution.
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| 28. |
- Hu, N., et al.
(författare)
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Polarimetric Imaging Using One Fractal SNSPD
- 2022
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Ingår i: 2022 Conference on Lasers and Electro-Optics, CLEO 2022. - : Institute of Electrical and Electronics Engineers Inc..
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Konferensbidrag (refereegranskat)abstract
- We demonstrate a polarimetric imaging system with one fractal superconducting nanowire single-photon detector and time-multiplexed photon-counting scheme, which allows us to obtain images with multiple types of contrast.
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| 29. |
- Hu, Xiaolong, et al.
(författare)
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Fractal superconducting nanowire single-photon detectors and their applications in polarimetric imaging
- 2024
-
Ingår i: Advanced Photon Counting Techniques XVIII. - : SPIE-Intl Soc Optical Eng.
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we review the research and development of the fractal superconducting nanowire single-photon detectors (SNSPDs), including our demonstrations of high-performance devices and systems with over 80% system detection efficiency, negligibly low residual polarization sensitivity, and low timing jitter. Using the fractal SNSPDs, we demonstrate full-Stokes polarimetric imaging LiDAR.
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| 30. |
- Hummel, Thomas, et al.
(författare)
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Gated- and optical biasing for SNSPDs
- 2023
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Ingår i: Frontiers in Optics: Proceedings Frontiers in Optics + Laser Science 2023, FiO, LS 2023. - : Optica Publishing Group.
-
Konferensbidrag (refereegranskat)abstract
- SNSPDs are usually limited to constant current bias operation due to the required room temperature auxiliary electronics. We show gated mode operation and low power biasing of SNSPDs with cryogenic integrated current sources.
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| 31. |
- Hummel, Thomas, et al.
(författare)
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Nanosecond gating of superconducting nanowire single-photon detectors using cryogenic bias circuitry
- 2023
-
Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 31:1, s. 610-625
-
Tidskriftsartikel (refereegranskat)abstract
- Superconducting nanowire single-photon detectors (SNSPDs) show near unity efficiency, low dark count rate, and short recovery time. Combining these characteristics with temporal control of SNSPDs broadens their applications as in active de-latching for higher dynamic range counting or temporal filtering for pump-probe spectroscopy or LiDAR. To that end, we demonstrate active gating of an SNSPD with a minimum off-to-on rise time of 2.4 ns and a total gate length of 5.0 ns. We show how the rise time depends on the inductance of the detector in combination with the control electronics. The gate window is demonstrated to be fully and freely, electrically tunable up to 500 ns at a repetition rate of 1.0 MHz, as well as ungated, free-running operation. Control electronics to generate the gating are mounted on the 2.3K stage of a closed-cycle sorption cryostat, while the detector is operated on the cold stage at 0.8 K. We show that the efficiency and timing jitter of the detector is not altered during the on-time of the gating window. We exploit gated operation to demonstrate a method to increase in the photon counting dynamic range by a factor 11.2, as well as temporal filtering of a strong pump in an emulated pump-probe experiment.
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| 32. |
- Jonsson, Mattias, et al.
(författare)
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Current Crowding in Nanoscale Superconductors within the Ginzburg-Landau Model
- 2022
-
Ingår i: Physical Review Applied. - : American Physical Society (APS). - 2331-7019. ; 17:6
-
Tidskriftsartikel (refereegranskat)abstract
- The current density in a superconductor with turnarounds or constrictions is nonuniform due to a geometrical current-crowding effect. This effect reduces the critical current in the superconducting structure compared to a straight segment and is of importance when designing superconducting devices. We investigate the current-crowding effect in numerical simulations within the generalized time-dependent Ginzburg-Landau (GTDGL) model. The results are validated experimentally by measuring the magnetic field dependence of the critical current in superconducting-nanowire structures, similar to those employed in single-photon detector devices. Comparing the results with London theory, we conclude that the reduction in critical current is significantly smaller in the GTDGL model. This difference is attributed to the current redistribution effect, which reduces the current density at weak points of the superconductor and counteracts the current-crowding effect. We numerically investigate the effect of the fill factor on the critical current in a meander and conclude that the reduction of the critical current is low enough to justify fill factors higher than 33% for applications where the detection efficiency is critical. Finally, we propose a meander design that can combine a high fill factor and low current crowding.
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| 33. |
- Jönsson, Mattias, et al.
(författare)
-
Current crowding in nanoscale superconductors within the Ginzburg-Landau model
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The current density in a superconductor with turnarounds or constrictions is non-uniform due to a geometrical current crowding effect. This effect reduces the critical current in the superconducting structure compared to a straight segment and is of importance when designing superconducting devices. We investigate the current crowding effect in numerical simulations within the generalized time-dependent Ginzburg-Landau (GTDGL) model. The results are validated experimentally by measuring the magnetic field dependence of the critical current in superconducting nanowire structures, similar to those employed in single-photon detector devices. Comparing the results with London theory, we conclude that the reduction in critical current is significantly smaller in the GTDGL model. This difference is attributed to the current redistribution effect, which reduces the current density in weak points of the superconductor and counteracts the current crowding effect. We numerically investigate the effect of fill factor on the critical current in a meander and conclude that the reduction of critical current is low enough to justify fill factors higher than 33 % for applications where detection efficiency is critical. Finally, we propose a novel meander design which can combine high fill factor and low current crowding.
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| 34. |
- Koeck, A., et al.
(författare)
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Multifunctional Nanoparticles - Key for Optimizing Chemical Nanosensors
- 2018
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Ingår i: ASDAM 2018 - Proceedings: 12th International Conference on Advanced Semiconductor Devices and Microsystems. - : IEEE. - 9781538674901 ; , s. 227-231
-
Konferensbidrag (refereegranskat)abstract
- Multifunctional nanoparticles are key for optimizing the performance of chemical sensor devices. We have fabricated a variety of nanosensor devices based on ultrathin metal oxide films and nanowires, which have been integrated on CMOS-based micro-hotplate chips. These sensors have been functionalized with metallic as well as bimetallic nanoparticles. We have demonstrated that Pt-NPs or NiPt-NPs, strongly increase the sensitivity to carbon monoxide and supress the cross selectivity to humidity in case of SnO2 thin film based devices. We have employed both nanoparticles synthesized in solution, which are ink-jet deposited, as well as nanoparticles, which are implemented by gas phase synthesis directly on the micro-hotplate chips. The Pt-functionalized SnO2-thin film sensors show a strongly increased response to CO, which is almost independent of humidity as compared to the bare SnO2-thin film sensor. The highest response of more than 90% has been achieved with NiPt-functionalized SnO2-thin film sensors at a very low operation temperature of only 150 degrees C.
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| 35. |
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| 36. |
- Lettner, Thomas, et al.
(författare)
-
Strain-controlled quantum dot fine-structure for entangled-photon generation at 1550 nm
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Entangled-photon generation at 1550nm in the telecom C-band is of critical importance, since it enables the realization of quantum communication protocols over long distance using deployed telecommunication infrastructure. InAs epitaxial quantum dots have recently enabled on-demand generation of entangled pairs of photons in this wavelength range. However, time-dependent state evolution, caused by the fine-structure splitting, currently limits the fidelity to a specific entangled state. Here, we show suppression of the fine-structure for InAs quantum dots using micromachined piezoelectric actuators and demonstrate generation of highly entangled photons in the telecom C-band. At the lowest fine-structure setting, we obtain a maximum fidelity of (90.0 ± 2.7)% (concurrence of (87.5 ± 3.1)%). The concurrence remains high also for moderate (weak) temporal-filtering, with values close to 80% (50%), corresponding to 30% (80%) of collected photons, respectively. The presented fine-structure control opens the way for the exploitation of entangled photons from quantum dots in fiber-based quantum communication protocols.
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| 37. |
- Lettner, Thomas, et al.
(författare)
-
Strain-Controlled Quantum Dot Fine Structure for Entangled Photon Generation at 1550 nm
- 2021
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 21:24, s. 10501-10506
-
Tidskriftsartikel (refereegranskat)abstract
- Entangled photon generation at 1550 nm in the telecom C-band is of critical importance as it enables the realization of quantum communication protocols over long distance using deployed telecommunication infrastructure. InAs epitaxial quantum dots have recently enabled on-demand generation of entangled photons in this wavelength range. However, time-dependent state evolution, caused by the fine-structure splitting, currently limits the fidelity to a specific entangled state. Here, we show fine-structure suppression for InAs quantum dots using micromachined piezoelectric actuators and demonstrate generation of highly entangled photons at 1550 nm. At the lowest fine-structure setting, we obtain a maximum fidelity of 90.0 +/- 2.7% (concurrence of 87.5 +/- 3.1%). The concurrence remains high also for moderate (weak) temporal filtering, with values close to 80% (50%), corresponding to 30% (80%) of collected photons, respectively. The presented fine-structure control opens the way for exploiting entangled photons from quantum dots in fiber-based quantum communication protocols.
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| 38. |
- Los, J. W.Niels, et al.
(författare)
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High-performance photon number resolving detectors for 850-950 nm wavelength range
- 2024
-
Ingår i: APL Photonics. - : AIP Publishing. - 2378-0967. ; 9:6
-
Tidskriftsartikel (refereegranskat)abstract
- Since their first demonstration in 2001 [Gol’tsman et al., Appl. Phys. Lett. 79, 705-707 (2001)], superconducting-nanowire single-photon detectors (SNSPDs) have witnessed two decades of great developments. SNSPDs are the detector of choice in most modern quantum optics experiments and are slowly finding their way into other photon-starved fields of optics. Until now, however, in nearly all experiments, SNSPDs were used as “binary” detectors, meaning that they could only distinguish between 0 and > = 1 photons, and photon number information was lost. Recent research has demonstrated proof-of-principle photon-number resolution (PNR) SNSPDs counting 2-5 photons. The photon-number-resolving capability is highly demanded in various quantum-optics experiments, including Hong-Ou-Mandel interference, photonic quantum computing, quantum communication, and non-Gaussian quantum state preparation. In particular, PNR detectors at the wavelength range of 850-950 nm are of great interest due to the availability of high-quality semiconductor quantum dots (QDs) [Heindel et al., Adv. Opt. Photonics 15, 613-738 (2023)] and high-performance cesium-based quantum memories [Ma et al., J. Opt. 19, 043001 (2017)]. In this paper, we demonstrate NbTiN-based SNSPDs with >94% system detection efficiency, sub-11 ps timing jitter for one photon, and sub-7 ps for 2 photons. More importantly, our detectors resolve up to 7 photons using conventional cryogenic electric readout circuitry. Through theoretical analysis, we show that the PNR performance of demonstrated detectors can be further improved by enhancing the signal-to-noise ratio and bandwidth of our readout circuitry. Our results are promising for the future of optical quantum computing and quantum communication.
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| 39. |
- Meng, Y., et al.
(författare)
-
Fractal superconducting nanowire avalanche photodetector at 1550 nm with 60% system detection efficiency and 1.05 polarization sensitivity
- 2020
-
Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 45:2, s. 471-474
-
Tidskriftsartikel (refereegranskat)abstract
- Superconducting nanowire (nanostrip) single-photon detectors (SNSPDs) have shown unprecedented detection efficiency and timing properties, but simultaneously achieving polarization-insensitive high detection efficiency, low dark-count rate (DCR), fast speed, and low timing jitter remains a challenge. Here we report on our design, fabrication, and characterization of a cascaded superconducting avalanche photodetector composed of 40 nm wide NbTiN nanowires patterned into fractal curves. At the base temperature of 2.7 K, the device exhibits 60 ± 3% system detection efficiency at the wavelength of 1550 nm, 1.05 polarization sensitivity, 220 cps DCR, 4 ns recovery time, and 45 ps timing jitter. This Letter not only demonstrates these combined properties on a single detector that was unobtainable previously, but also shows that that current-crowding effect remarkably permits decent internal detection efficiency. These counter-intuitive results expand the understanding pertaining to the device physics of SNSPDs.
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| 40. |
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| 41. |
- Meng, Yun, et al.
(författare)
-
Fractal Superconducting Nanowires Detect Infrared Single Photonswith 84% System Detection Efficiency, 1.02 Polarization Sensitivity,and 20.8 ps Timing Resolution br
- 2022
-
Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 9:5, s. 1547-1553
-
Tidskriftsartikel (refereegranskat)abstract
- The near-unity system detection efficiency (SDE) and excellent timing resolution of superconducting nanowiresingle-photon detectors (SNSPDs), combined with their other merits, have enabled many classical and quantum photonicapplications. However, the prevalent design based on meandering nanowires makes SDE dependent on the polarization states of theincident photons; for unpolarized light, the major merit of high SDE would get compromised, which could be detrimental to photon-starved applications. Here, we create SNSPDs with an arced fractal geometry that almost completely eliminates this polarizationdependence of the SDE, and we experimentally demonstrate 84 +/- 3% SDE, 1.02-0.02+0.06polarization sensitivity at the wavelength of1575 nm, and 20.8 ps timing jitter in a 0.1 W closed-cycle Gifford-McMahon cryocooler, at the base temperature of 2.0 K. Thisdemonstration provides a novel, practical device structure of SNSPDs, allowing for operation in the visible, near-infrared, and mid-infrared spectral ranges, and paves the way for polarization-insensitive single-photon detection with high SDE and high timingresolution.
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| 42. |
- Moody, Galan, et al.
(författare)
-
2022 Roadmap on integrated quantum photonics
- 2022
-
Ingår i: Journal of Physics: Photonics. - : IOP Publishing. - 2515-7647. ; 4:1
-
Tidskriftsartikel (refereegranskat)abstract
- Integrated photonics will play a key role in quantum systems as they grow from few-qubit prototypes to tens of thousands of qubits. The underlying optical quantum technologies can only be realized through the integration of these components onto quantum photonic integrated circuits (QPICs) with accompanying electronics. In the last decade, remarkable advances in quantum photonic integration have enabled table-top experiments to be scaled down to prototype chips with improvements in efficiency, robustness, and key performance metrics. These advances have enabled integrated quantum photonic technologies combining up to 650 optical and electrical components onto a single chip that are capable of programmable quantum information processing, chip-to-chip networking, hybrid quantum system integration, and high-speed communications. In this roadmap article, we highlight the status, current and future challenges, and emerging technologies in several key research areas in integrated quantum photonics, including photonic platforms, quantum and classical light sources, quantum frequency conversion, integrated detectors, and applications in computing, communications, and sensing. With advances in materials, photonic design architectures, fabrication and integration processes, packaging, and testing and benchmarking, in the next decade we can expect a transition from single- and few-function prototypes to large-scale integration of multi-functional and reconfigurable devices that will have a transformative impact on quantum information science and engineering.
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| 43. |
- Nikoulis, G., et al.
(författare)
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NanoMaterialsCAD : Flexible Software for the Design of Nanostructures
- 2021
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Ingår i: Advanced Theory and Simulations. - : Wiley. - 2513-0390. ; 4:1
-
Tidskriftsartikel (refereegranskat)abstract
- NanoMaterialsCAD is a new open source tool dedicated to the creation, manipulation, and 3D visualization of crystalline structures at the nanoscale. It is designed for preprocessing atomistic configurations to be used as input for atomistic (e.g., molecular dynamics or Monte Carlo) or ab initio (e.g., density functional theory) computer simulations. It offers several tools for designing complex nanostructures (including nanoparticles, nanowires, nanotubes, nanoscrolls, etc., and combinations/permutations of them) which are either lacking or cumbersome in other existing packages. Through its intuitive graphical user interface (GUI) it enables facile ways to design and modify the size/shape and relative positions of nanoobjects while observing the changes in real time. NanoMaterialsCAD is written in C++, and exploits Open Graphics Library (OpenGL) (for the GUI), Win32API (for interaction with Windows), and Assembly (for fast data management). The source code and executable file are available for download from GitHub (https://github.com/cossphy/NanoMaterialsCAD). It is aspired that NanoMaterialsCAD will be adopted by the nanomaterials modeling community as a valuable resource; to this end it will be kept improving, incorporating more nanostructures, and adding extra functionalities to its toolbox.
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| 44. |
- Prencipe, Alessandro, et al.
(författare)
-
Wavelength meter on thin film lithium niobate based on superconducting single photon detectors
- 2023
-
Ingår i: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023. - : Institute of Electrical and Electronics Engineers (IEEE).
-
Konferensbidrag (refereegranskat)abstract
- Photonic integrated circuits (PICs) present significant benefits with respect to table-top optical systems regarding footprint, stability, and power consumption. Among the materials used to fabricate PICs, thin film lithium niobate (TFLN) is one of the most attractive ones, as its χ(2) nonlinearity and electro-optic properties allow to implement on-chip light generation and routing [1]. On-chip detection of light has also been demonstrated on TFLN, based on the waveguide integration of superconducting nanowire single photon detectors (SNSPDs) [1]. Combining efficient detectors with TFLN nanophotonic waveguides holds promises for the realization of quantum photonics experiments fully on-chip. On the other hand, the sensitivity of SNSPDs changes with the wavelength of the detected photons [2], setting a boundary to the longest detectable wavelength and limiting the use of the wide transparency window of TFLN. However, this wavelength dependency in the response of SNSPDs can be leveraged to achieve new on-chip functionalities. In this work, by performing a straightforward analysis of the light signal measured at different bias currents [2], we operate hairpin SNSPDs on TFLN as waveguide-integrated wavelength-meters in the telecom bandwidth.
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| 45. |
- Prencipe, Alessandro, et al.
(författare)
-
Wavelength-Sensitive Superconducting Single-Photon Detectors on Thin Film Lithium Niobate Waveguides
- 2023
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 23:21, s. 9748-9752
-
Tidskriftsartikel (refereegranskat)abstract
- Lithium niobate, because of its nonlinear and electro-optical properties, is one of the materials of choice for photonic applications. The development of nanostructuring capabilities of thin film lithium niobate (TFLN) permits fabrication of small footprint, low-loss optical circuits. With the recent implementation of on-chip single-photon detectors, this architecture is among the most promising for realizing on-chip quantum optics experiments. In this Letter, we report on the implementation of superconducting nanowire single-photon detectors (SNSPDs) based on NbTiN on 300 nm thick TFLN ridge nano-waveguides. We demonstrate a waveguide-integrated wavelength meter based on the photon energy dependence of the superconducting detectors. The device operates at the telecom C- and L-bands and has a footprint smaller than 300 × 180 μm2 and critical currents between ∼12 and ∼14 μA, which ensures operation with minimum heat dissipation. Our results hold promise for future densely packed on-chip wavelength-multiplexed quantum communication systems.
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| 46. |
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| 47. |
- Sidorova, M., et al.
(författare)
-
Magnetoconductance and photoresponse properties of disordered NbTiN films
- 2021
-
Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 104:18
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the experimental study of phonon properties and electron-phonon scattering in thin superconducting NbTiN films, which are intensively exploited in various applications. Studied NbTiN films with sub-10-nm thicknesses are disordered with respect to electron transport, the Ioffe-Regel parameter of kFle = 2.5-3.0 (kF is the Fermi wave vector, and le is the electron mean free path), the inelastic electron-phonon interaction, and the product qTle << 1 (qT is the wave vector of a thermal phonon). By means of magnetoconductance and photoresponse techniques, we derive the inelastic electron-phonon scattering rate 1/tau e-ph and determine sound velocities and phonon heat capacities. In the temperature range from 12 to 20 K, the scattering rate varies with temperature as 1/tau e-ph proportional to T 3.45 +/- 0.05; its value extrapolated to 10 K amounts to approximately 1/16 ps. Making a comparative analysis of our films and other films used in superconducting devices, such as polycrystalline granular NbN and amorphous WSi, we find a systematic reduction of the sound velocity in all these films by about 50% compared to the corresponding bulk crystalline materials. A corresponding increase in the phonon heat capacities in all these films is, however, less than the Debye model predicts. We attribute these findings to reduced film dimensionality and film morphology.
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| 48. |
- Sidorova, M., et al.
(författare)
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Phonon heat capacity and self-heating normal domains in NbTiN nanostrips
- 2022
-
Ingår i: Superconductors Science and Technology. - : IOP Publishing. - 0953-2048 .- 1361-6668. ; 35:10
-
Tidskriftsartikel (refereegranskat)abstract
- Self-heating normal domains in thin superconducting NbTiN nanostrips with the granular structure were characterized via steady-state hysteretic current-voltage characteristics measured at different substrate temperatures. The temperature dependence and the magnitude of the current, which sustains a domain in equilibrium at different voltages, can only be explained with a phonon heat capacity noticeably less than expected for 3D Debye phonons. This reduced heat capacity coincides with the value obtained earlier from magnetoconductance and photoresponse studies of the same films. The rate of heat flow from electrons at a temperature T-e to phonons in the substrate at a temperature T-B is proportional to (T (p) (e) - T (p)(B)) with the exponent p approximate to 3, which differs from the exponents for heat flows mediated by the electron-phonon interaction or by escaping of 3D Debye phonons via the film/substrate interface. We attribute both findings to the effect of grains on the phonon spectrum of thin NbTiN films. Our findings are significant for understanding the thermal transport in superconducting devices exploiting thin granular films.
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| 49. |
- Staffas, Theodor, et al.
(författare)
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3D scanning quantum LIDAR
- 2022
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Ingår i: 2022 Conference on Lasers and Electro-Optics, CLEO 2022. - : Institute of Electrical and Electronics Engineers Inc..
-
Konferensbidrag (refereegranskat)abstract
- Light Detection and Ranging (LIDAR) is a powerful imaging technique. By utilising a superconducting nanowire single photon detector (SNSPD) we construct a 3D scanning LIDAR system operating with eye-safe infrared laser pulses and millimeter precision.
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| 50. |
- Steinhauer, Stephan
(författare)
-
Gas Sensors Based on Copper Oxide Nanomaterials : A Review
- 2021
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Ingår i: CHEMOSENSORS. - : MDPI AG. - 2227-9040. ; 9:3
-
Forskningsöversikt (refereegranskat)abstract
- Metal oxide semiconductors have found widespread applications in chemical sensors based on electrical transduction principles, in particular for the detection of a large variety of gaseous analytes, including environmental pollutants and hazardous gases. This review recapitulates the progress in copper oxide nanomaterial-based devices, while discussing decisive factors influencing gas sensing properties and performance. Literature reports on the highly sensitive detection of several target molecules, including volatile organic compounds, hydrogen sulfide, carbon monoxide, carbon dioxide, hydrogen and nitrogen oxide from parts-per-million down to parts-per-billion concentrations are compared. Physico-chemical mechanisms for sensing and transduction are summarized and prospects for future developments are outlined.
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