56 research outputs found
Nonlinear characteristics of Ti, Nb, and NbN superconducting resonators for parametric amplifiers
Superconducting resonators and parametric amplifiers are important components
in scientific systems such as kinetic inductance detector arrays,
frequency-domain multiplexers for other superconducting bolometers,
spin-ensemble based memories, and circuit quantum electrodynamics
demonstrators. In this paper, we report microwave measurements of
superconducting Ti, Nb, and NbN resonators and their use as parametric
amplifiers. These half-wave resonators were fabricated under near identical
sputtering and lithographic conditions to ensure a like-for-like comparison of
material properties. We report a wide range of properties and behaviours in
terms of transition temperatures, resistivities, rate-limiting nonlinear
response times, nonlinear dissipation, signs of the nonlinear inductances and
their dependences on temperature and resonance harmonic. We have successfully
operated Nb and NbN resonators as high gain parametric amplifiers, achieving
greater than of power amplification. We have shown that for a
half-wave resonator, amplification can be realised not only in the fundamental
resonance but also in any of the higher harmonic resonances. Further, for
materials with high transition temperatures, e.g. Nb and NbN, amplification can
be achieved at , i.e. a temperature maintained by a pulse
tube cooler. Finally, in materials systems that have very fast response times,
e.g. NbN, we have found that a cross-harmonic type of amplification can be
achieved by placing pump tone in a different resonant mode as the signal and
the idler. This wide range of observations will have important implications on
the design and application of superconducting parametric amplifiers
Suppressed-gap millimetre wave kinetic inductance detectors using DC-bias current
Funder: CSC Cambridge ScholarshipAbstract: In this study, we evaluate the suitability of using DC-biased aluminium resonators as low-frequency kinetic inductance detectors capable of operating in the frequency range of 50β120 GHz. Our analysis routine for supercurrent-biased resonators is based on the Usadel equations and gives outputs including density of states, complex conductivities, transmission line properties, and quasiparticle lifetimes. Results from our analysis confirm previous experimental observations on resonant frequency tuneability and retention of high quality factor. Crucially, our analysis suggests that DC-biased resonators demonstrate significantly suppressed superconducting density of states gap. Consequently these resonators have lower frequency detection threshold and are suitable materials for low-frequency kinetic inductance detectors
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Suppressed-gap millimetre wave kinetic inductance detectors using DC-bias current
Funder: CSC Cambridge ScholarshipIn this study, we evaluate the suitability of using DC-biased aluminium
resonators as low-frequency kinetic inductance detectors operating in the
frequency range of 50 - 120 GHz. Our analysis routine for supercurrent-biased
resonators is based on the Usadel equations and gives outputs including density
of states, complex conductivities, transmission line properties, and
quasiparticle lifetimes. Results from our analysis confirm previous
experimental observations on resonant frequency tuneability and retention of
high quality factor. Crucially, our analysis suggests that DC-biased resonators
demonstrate significantly suppressed superconducting density of states gap.
Consequently these resonators have lower frequency detection threshold and are
suitable materials for low-frequency kinetic inductance detectors
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Nonlinear Properties of Supercurrent-Carrying Single- and Multi-Layer Thin-Film Superconductors
Funder: China Scholarship Council; doi: http://dx.doi.org/10.13039/501100004543Abstract: Superconducting thin films are central to the operation of many kinds of quantum sensors and quantum computing devices: kinetic inductance detectors (KIDs), travelling-wave parametric amplifiers (TWPAs), qubits, and spin-based quantum memory elements. In all cases, the nonlinearity resulting from the supercurrent is a critical aspect of behaviour, either because it is central to the operation of the device (TWPA), or because it results in nonideal second-order effects (KID). Here, we present an analysis of supercurrent-carrying superconducting thin films that is based on the generalized Usadel equations. Our analysis framework is suitable for both homogeneous and multi-layer thin films, and can be used to calculate the resulting density of states, superconducting transition temperature, superconducting critical current, complex conductivities, complex surface impedances, transmission line propagation constants, and nonlinear kinetic inductances in the presence of supercurrent. Our analysis gives the scale of kinetic inductance nonlinearity (Iβ) for a given material combination and geometry, and is important in optimizing the design of detectors and amplifiers in terms of materials, geometries, and dimensions. To investigate the validity of our analysis across a wide range of supercurrent, we have measured the transition temperatures of superconducting thin films as a function of DC supercurrent. These measurements show good agreement with our theoretical predictions in the experimentally relevant range of current values
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Nonlinear Properties of Supercurrent-Carrying Single- and Multi-Layer Thin-Film Superconductors
Funder: China Scholarship Council; doi: http://dx.doi.org/10.13039/501100004543Abstract: Superconducting thin films are central to the operation of many kinds of quantum sensors and quantum computing devices: kinetic inductance detectors (KIDs), travelling-wave parametric amplifiers (TWPAs), qubits, and spin-based quantum memory elements. In all cases, the nonlinearity resulting from the supercurrent is a critical aspect of behaviour, either because it is central to the operation of the device (TWPA), or because it results in nonideal second-order effects (KID). Here, we present an analysis of supercurrent-carrying superconducting thin films that is based on the generalized Usadel equations. Our analysis framework is suitable for both homogeneous and multi-layer thin films, and can be used to calculate the resulting density of states, superconducting transition temperature, superconducting critical current, complex conductivities, complex surface impedances, transmission line propagation constants, and nonlinear kinetic inductances in the presence of supercurrent. Our analysis gives the scale of kinetic inductance nonlinearity (Iβ) for a given material combination and geometry, and is important in optimizing the design of detectors and amplifiers in terms of materials, geometries, and dimensions. To investigate the validity of our analysis across a wide range of supercurrent, we have measured the transition temperatures of superconducting thin films as a function of DC supercurrent. These measurements show good agreement with our theoretical predictions in the experimentally relevant range of current values
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