Regensburg 2022 – scientific programme

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SYUK: Symposium United Kingdom as Guest of Honor

SYUK 2: United Kingdom as Guest of Honor II

SYUK 2.5: Invited Talk

Wednesday, September 7, 2022, 17:15–17:45, H2

Superconducting Quantum Interference Devices for applications at mK temperatures — •Sebastian Kempf — Institute of Micro- and Nanoelectronic Systems, Karlsruhe Institute of Technology, Hertzstraße 16, 76187 Karlsruhe, Germany.

Superconducting quantum interference devices (SQUIDs) are among the most sensitive wideband devices for measuring any quantity that can be naturally converted into magnetic flux. They are intrinsically compatible with Kelvin and sub-Kelvin operation temperatures, offer great sensitivity to even tiniest signals and often show a noise level close to the quantum limit. For this reason, SQUIDs are routinely used for various applications such as investigating magnetic nanoparticles, 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 susceptible to suffer from parasitic Joule heating, often preventing to reach very low sub-K temperatures.

Using the example of cryogenic low-impedance 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 dispersive SQUID readout allow for performing SQUID based measurements down to very low temperatures. Moreover, we discuss a SQUID based multiplexer allowing for simultaneous readout of hundreds and thousands of signal sources with only several nW of power.