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- Gutierrez Latorre, Martí, 1993
(författare)
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Chip-based magnetic levitation of superconducting microparticles
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Magnetically levitated superconductors are extremely isolated from the environment, their mechanical properties can be tuned magnetically, and can be coupled to quantum systems such as superconducting quantum circuits. As such, they are a promising experimental platform for the creation of massive spatial quantum states that would test quantum mechanics in a hitherto unexplored parameter regime. Furthermore, they could be used to build ultrasensitive detectors of accelerations and forces, which could find applications in seismology, navigation, geodesy, or dark matter detection. This thesis is about the development and demonstration of a chip-based magnetic levitation platform for um-sized superconducting particles. To this end, we have modeled, designed, and fabricated micrometer-scale superconducting particles as well as chip-based magnetic traps based on planar superconducting coils. We have detected the center-of-mass motion of the levitated particles magnetically, with integrated superconducting coils that transport the signal of the particle motion to a SQUID magnetometer. We demonstrated stable levitation of 50um diameter particles over several days at millikelvin temperatures. This high stability allowed us to thoroughly characterize the particle motion and show that our model of the magnetic trap and the detection scheme captures the nonlinear behavior of the center-of-mass motion. These nonlinearities are observed due to large motional amplitudes caused by the coupling between the particle motion and cryostat vibrations. We have devised a cryogenic vibration isolation system based on an elastic pendulum that mitigates this effect and has enabled ring-down measurements of the center-of-mass motion that give quality factors up to 10^5. Furthermore, we have shown that the mechanical properties of the levitated particle can be controlled. We have tuned the trap frequencies from 30Hz to 180Hz by changing the current in the trap coils, and we have also demonstrated control over the motional amplitude of the particle motion via feedback using feedback coils in the chip to exert an additional magnetic force on the particle. This thesis demonstrates magnetic levitation of superconducting microparticles on a chip as a novel platform for chip-based quantum experiments with um-sized particles and ultrasensitive force and acceleration sensors.
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| 2. |
- Gutierrez Latorre, Martí, 1993, et al.
(författare)
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Chip-based superconducting traps for levitation of micrometer-sized particles in the Meissner state
- 2020
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Ingår i: Superconductor Science and Technology. - : IOP Publishing. - 0953-2048 .- 1361-6668. ; 33:10
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Tidskriftsartikel (refereegranskat)abstract
- We present a detailed analysis of two chip-based superconducting trap architectures capable of levitating micrometer-sized superconducting particles in the Meissner state. These architectures are suitable for performing novel quantum experiments with more massive particles or for force and acceleration sensors of unprecedented sensitivity. We focus in our work on a chip-based anti-Helmholtz coil-type trap (AHC) and a planar double-loop (DL) trap. We demonstrate their fabrication from superconducting Nb films and the fabrication of superconducting particles from Nb or Pb. We apply finite element modeling (FEM) to analyze these two trap architectures in detail with respect to trap stability and frequency. Crucially, in FEM we account for the complete three-dimensional geometry of the traps, finite magnetic field penetration into the levitated superconducting particle, demagnetizing effects, and flux quantization. We can, thus, analyze trap properties beyond assumptions made in analytical models. We find that realistic AHC traps yield trap frequencies well above 10 kHz for levitation of micrometer-sized particles and can be fabricated with a three-layer process, while DL traps enable trap frequencies below 1 kHz and are simpler to fabricate in a single-layer process. Our numerical results guide future experiments aiming at levitating micrometer-sized particles in the Meissner state with chip-based superconducting traps. The modeling we use is also applicable in other scenarios using superconductors in the Meissner state, such as for designing superconducting magnetic shields or for calculating filling factors in superconducting resonators.
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| 3. |
- Gutierrez Latorre, Martí, 1993, et al.
(författare)
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Superconducting Microsphere Magnetically Levitated in an Anharmonic Potential with Integrated Magnetic Readout
- 2023
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Ingår i: Physical Review Applied. - 2331-7019. ; 19:5
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Tidskriftsartikel (refereegranskat)abstract
- Magnetically levitated superconducting microparticles offer a promising path to quantum experiments with picogram to microgram objects. In this work, we levitate a 700 ng∼1017amu superconducting microsphere in a magnetic chip trap in which detection is integrated. We measure the center-of-mass motion of the particle using a dc superconducting quantum interference device magnetometer. The trap frequencies are continuously tunable between 30 and 160 Hz and the particle remains stably trapped over days in a dilution-refrigerator environment. We characterize the motional-amplitude-dependent frequency shifts, which arise from trap anharmonicities, namely, Duffing nonlinearities and mode couplings. We explain this nonlinear behavior using finite-element modeling of the chip-based trap potential. This work may constitute a first step toward quantum experiments and ultrasensitive inertial sensors with magnetically levitated superconducting microparticles.
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| 4. |
- Niepce, David, 1984, et al.
(författare)
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Geometric scaling of two-level-system loss in superconducting resonators
- 2020
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Ingår i: Superconductor Science and Technology. - : IOP Publishing. - 0953-2048 .- 1361-6668. ; 33:2
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Tidskriftsartikel (refereegranskat)abstract
- We perform an experimental and numerical study of dielectric loss in superconducting microwave resonators at low temperature. Dielectric loss, due to two-level systems, is a limiting factor in several applications, e.g. superconducting qubits, Josephson parametric amplifiers, microwave kinetic-inductance detectors, and superconducting single-photon detectors. Our devices are made of disordered NbN, which, due to magnetic-field penetration, necessitates 3D finite-element simulation of the Maxwell-London equations at microwave frequencies to accurately model the current density and electric field distribution. From the field distribution, we compute the geometric filling factors of the lossy regions in our resonator structures and fit the experimental data to determine the intrinsic loss tangents of its interfaces and dielectrics. We put emphasis on the loss caused by a spin-on-glass resist such as hydrogen silsesquioxane (HSQ), used for ultrahigh lithographic resolution relevant to the fabrication of nanowires. We find that, when used, HSQ is the dominant source of loss, with a loss tangent ofδHSQi=× 10-3 SRC.
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| 5. |
- Zehri, Abdelhafid, 1989, et al.
(författare)
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High porosity and light weight graphene foam heat sink and phase change material container for thermal management
- 2020
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Ingår i: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 31:42
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Tidskriftsartikel (refereegranskat)abstract
- During the last decade, graphene foam emerged as a promising high porosity 3-dimensional (3D) structure for various applications. More specifically, it has attracted significant interest as a solution for thermal management in electronics. In this study, we investigate the possibility to use such porous materials as a heat sink and a container for a phase change material (PCM). Graphene foam (GF) was produced using chemical vapor deposition (CVD) process and attached to a thermal test chip using sintered silver nanoparticles (Ag NPs). The thermal conductivity of the graphene foam reached 1.3 W m(-1)K(-1), while the addition of Ag as a graphene foam silver composite (GF/Ag) enhanced further its effective thermal conductivity by 54%. Comparatively to nickel foam, GF and GF/Ag showed lower junction temperatures thanks to higher effective thermal conductivity and a better contact. A finite element model was developed to simulate the fluid flow through the foam structure model and showed a positive and a non-negligible contributions of the secondary microchannel within the graphene foam. A ratio of 15 times was found between the convective heat flux within the primary and secondary microchannel. Our paper successfully demonstrates the possibility of using such 3D porous material as a PCM container and heat sink and highlight the advantage of using the carbon-based high porosity material to take advantage of its additional secondary porosity.
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| 6. |
- Zhang, Q., et al.
(författare)
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Mechanical property and reliability of bimodal nano-silver paste with Ag-coated SiC particles
- 2019
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Ingår i: Soldering and Surface Mount Technology. - 1758-6836 .- 0954-0911. ; 31:4, s. 193-202
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Tidskriftsartikel (refereegranskat)abstract
- © 2019, Emerald Publishing Limited. Purpose: This study aims to develop a bimodal nano-silver paste with improved mechanical property and reliability. Silicon carbide (SiC) particles coated with Ag were introduced in nano-silver paste to improve bonding strength between SiC and Ag particles and enhance high-temperature stability of bimodal nano-silver paste. The effect of sintering parameters such as sintering temperature, sintering time and the proportion of SiC particles on mechanical property and reliability of sintered bimodal nano-silver structure were investigated. Design/methodology/approach: Sandwich structures consist of dummy chips and copper substrates with nickel and silver coating bonded by nano-silver paste were designed for shear testing. Shear strength testing was conducted to study the influence of SiC particles proportions on the mechanical property of sintered nano-silver joints. The reliability of the bimodal nano-silver paste was evaluated experimentally by means of shear test for samples subjected to thermal aging test at 150°C and humidity and temperature testing at 85°C and 85 per cent RH, respectively. Findings: Shear strength was enhanced obviously with the increase of sintering temperature and sintering time. The maximum shear strength was achieved for nano-silver paste sintered at 260°C for 10 min. There was a negative correlation between the proportion of SiC particles and shear strength. After thermal aging testing and humidity and temperature testing for 240 h, the shear strength decreased a little. High-temperature stability and high-hydrothermal stability were improved by the addition of SiC particles. Originality/value: Submicron-scale SiC particles coated with Ag were used as alternative materials to replace part of nano-silver particles to prepare bimodal nano-silver paste due to its high thermal conductivity and excellent mechanical property.
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