Electromagnetic Properties of Superconductors

Pöpel, R.

doi:10.1007/978-3-642-95592-1_3

Cited by 13 publications

(6 citation statements)

References 26 publications

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“…Furthermore, we investigated the effect of a superconductor's surface impedance to validate the perfect conductor boundary condition. We confirmed that the participation ratio and resonant frequency changes were less than 0.1% at 20 mK when the surface impedance of a typical superconducting film is taken into account [38,52,53]. Thus, we safely applied a perfect conductor boundary condition for superconducting films.…”

Section: Parameter Settings and In-depth Analysissupporting

confidence: 67%

Shape optimization of superconducting transmon qubits for low surface dielectric loss

Eun,

Park,

Seo

et al. 2023

J. Phys. D: Appl. Phys.

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Surface dielectric loss of superconducting transmon qubit is believed as one of the dominant sources of decoherence. Reducing surface dielectric loss of superconducting qubit is known to be a great challenge for achieving high quality factor and a long relaxation time (T 1). Changing the geometry of capacitor pads and junction wire of transmon qubit makes it possible to engineer the surface dielectric loss. In this paper, we present the shape optimization approach for reducing Surface dielectric loss in transmon qubit. The capacitor pad and junction wire of the transmon qubit are shaped as spline curves and optimized through the combination of the finite-element method and global optimization algorithm. Then, we compared the surface participation ratio, which represents the portion of electric energy stored in each dielectric layer and proportional to two-level system (TLS) loss, of optimized structure and existing geometries to show the effectiveness of our approach. The result suggests that the participation ratio of capacitor pad, and junction wire can be reduced by 15 ∼ 18% and 22 ∼ 26% compared to previous designs through shape optimization, while overall footprint and anharmonicity maintain acceptable value. As a result, the TLS-limited quality factor and corresponding T 1 were increased by approximately 21.6%.

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Section: Parameter Settings and In-depth Analysissupporting

confidence: 67%

Shape optimization of superconducting transmon qubits for low surface dielectric loss

Eun,

Park,

Seo

et al. 2023

J. Phys. D: Appl. Phys.

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“…10, pp. 1371-1376, 1989. He is a group leader at the California Institute of Technology's Jet Propulsion Laboratory.…”

mentioning

confidence: 99%

Characterization of low-noise quasi-optical SIS mixers for the submillimeter band

Gaidis

Leduc

Bin

et al. 1996

IEEE Trans. Microwave Theory Techn.

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Abstruct-We report on the development of low-noise quasioptical SIS mixers for the frequency range 400-850 GHz. The mixers utilize twin-slot antennas, two-junction tuning circuits, and Nb-trilayer junctions. Fourier-transform spectrometry has been used to verify that the frequency response of the devices is well predicted by computer simulations. The 400-850 GHz frequency band can be covered with four separate fixed-tuned mixers. We measure uncorrected double-sideband receiver noise temperatures around S h u / k~ to 700 GHz, and better than 540 K at 808 GHz. These results are among the best reported to date for broadband heterodyne receivers.

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“…Secondly connecting the high impedance "end-loaded" stub to the low impedance transmission line results in an huge discontinuity which increases the effective electrical length of the "end-loaded" stub. And lastly, as the frequency of operation approaches that of the bandgap energy of niobium (700 GHz), the absorption loss in the superconducting material is expected to increase very rapidly 37,38 and should be taken into account. The "butterfly" RF matching network as shown in Figure 5 overcomes some of these difficulties.…”

Section: Sis Tunnel Junction Design Below the Bandgap Frequency Of Nimentioning

confidence: 99%

“…To avoid this problem, we explored the idea of fabricating the junction on a 1 µm Si 3 N 4 membrane 31 . At the frequencies of interest, the photons have energies larger than the superconducting energy gap of niobium, 2∆, and are able to break Cooper pairs within the superconductor 37,38 . This results in a large absorption loss in the niobium transmission line situated in front of the mixer, thereby seriously degrading the sensitivity of the mixer.…”

Section: Sis Tunnel Junction Design Above the Bandgap Frequency Of Nimentioning

confidence: 99%

<title>Heterodyne instrumentation at the CSO</title>

et al. 1998

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The Caltech Submillimeter observatory (CSO) is one of the World's premier submillimeter telescopes. It consists of a 10.4 meter diameter Leighton radio dish situated in a compact dome near the summit of Mauna Kea, Hawaii. The telescope has been operating under a contract from the National Science Foundation on a regular basis since 1988. For the first time heterodyne Superconducting-Insulating-Superconducting (SIS) receivers with a 1 GHz intermediate frequency (IF) are available for the entire 180 -950 GHz Submillimeter band. To enhance the extra-galactic capabilities of the observatory and to allow interferometry with the upcoming Submillimeter Array (SMA) project, we are actively working towards upgrading all heterodyne instruments with a 3 GHz IF bandwidth. Concurrent to the planned IF upgrade, we are constructing a dual polarization beam switching 345 GHz extra-galactic receiver, also with a 3 GHz IF bandwidth. Ideally, this instrument will give the CSO a factor of 8 improvement in integration time over the current 345 GHz receiver, and will be ideally suited for the study of highly red-shifted extra-galactic sources.

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Electromagnetic Properties of Superconductors

Cited by 13 publications

References 26 publications

Shape optimization of superconducting transmon qubits for low surface dielectric loss

Shape optimization of superconducting transmon qubits for low surface dielectric loss

Characterization of low-noise quasi-optical SIS mixers for the submillimeter band

<title>Heterodyne instrumentation at the CSO</title>

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