Event Details

Superconducting Quantum Interference Devices (SQUIDs) for science experiments at ultra-low temperatures by Prof. Dr. Sebastian Kempf

Superconducting Quantum Interference Devices (SQUIDs) for science experiments at ultra-low temperatures

Prof. Dr. Sebastian Kempf

Karlsruhe Institute of Technology (KIT)

9th December at 3pm

Location: C36 and online

Abstract

Superconducting quantum interference devices (SQUIDs) are among the most sensitive wideband devices for measuring any physical quantity that can be naturally converted into a change of magnetic flux. Due to their physical nature, i.e. employing superconducting micro- and nanostructures as well as quantum effects, they are intrinsically compatible with kelvin, millikelvin and potentially microkelvin operation temperatures. Moreover, they offer great sensitivity to even tiniest signals and often show a noise level very close to the quantum limit. For this reason, SQUIDs are routinely used for various applications such as investigating magnetic nanoparticles at low and ultralow temperatures, diagnostics in health care, "non-invasive" mineral deposit exploration, low-field magnetic resonance imaging, quantum information processing or the readout of low-impedance cryogenic particle detectors. However, SQUID based measurements are known to be potentially suffer from parasitic Joule heating, often preventing to reach very low sub-K temperatures. Using the example of cryogenic single particle detectors, we discuss strategies to minimize parasitic SQUID Joule heating to ultimately operate single-channel detectors as well as mid- and large-scale detector arrays at lowest mK temperatures. We particularly show that on-chip thermal decoupling of shunt resistors and sample environment or dis- persive SQUID readout allow for performing SQUID based measurements down to very low temperatures. Moreover, we discuss a SQUID based multiplexing techniques allowing for simultaneous readout of hundreds and thousands of signal sources with only several nW of power. The latter technique might be also a route for more extensively using SQUID at ultralow temperatures.

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