The performance and accuracy of quantum electronics is substantially degraded when the temperature of the electrons in the devices is too high. The electron temperature can be reduced with appropriate thermal anchoring and by filtering both the low frequency and radio frequency noise. Ultimately, for high performance filters the electron temperature can approach the phonon temperature (as measured by resistive thermometers) in a dilution refrigerator. In this application note, the method for measuring the electron temperature in a typical quantum electronics device using Coulomb blockade thermometry is described. This technique is applied to find the readily achievable electron temperature in the device when using the QFilter provided by QDevil. With our thermometry measurements, using a single GaAs/AlGaAs quantum dot in an optimized experimental setup, we determined an electron temperature of 28 $\pm$ 2 mK for a dilution refrigerator base temperature of 18 mK.The performance and accuracy of quantum electronics is substantially degraded when the temperature of the electrons in the devices is too high. The electron temperature can be reduced with appropriate thermal anchoring and by filtering both the low frequency and radio frequency noise. Ultimately, for high performance filters the electron temperature can approach the phonon temperature (as measured by resistive thermometers) in a dilution refrigerator. In this application note, the method for measuring the electron temperature in a typical quantum electronics device using Coulomb blockade thermometry is described. This technique is applied to find the readily achievable electron temperature in the device when using the QFilter provided by QDevil. With our thermometry measurements, using a single GaAs/AlGaAs quantum dot in an optimized experimental setup, we determined an electron temperature of 28 $\pm$ 2 mK for a dilution refrigerator base temperature of 18 mK.

arXiv:2403.16305Mar 24, 20240 citations

Evaluation of Low-Power Single-Flux-Quantum Circuits Fabricated with a 250 A/cm2 Nb/AlOx/Nb Josephson Junction Process Using a Dilution Refrigerator

Masamitsu Tanaka, Tomoki UEDA, Yoshihiro KITAGAWA +2 more

We report the measurement results of the low-power single-flux-quantum (SFQ) circuits below 20 mK using a dilution refrigerator. We have been developing the SFQ circuits using a lowered critical current density process (250 A/cm2) and low-voltage design (0.1–0.5 mV) toward digital signal processing near superconductor quantum bits. So far, we have designed several basic SFQ cells, including wiring elements, flip-flops, and logic gates, using the four Nb planarized layer process and obtained the correct operation at 300 mK. In this study, we tested several SFQ circuits aiming to evaluate the operation at the mixing chamber stage of a dilution refrigerator. Our experimental results show that there was almost no change of device parameters, such as critical current values of Josephson junctions, or operating margins of the basic cells between 300 mK and 16 mK.We report the measurement results of the low-power single-flux-quantum (SFQ) circuits below 20 mK using a dilution refrigerator. We have been developing the SFQ circuits using a lowered critical current density process (250 A/cm2) and low-voltage design (0.1–0.5 mV) toward digital signal processing near superconductor quantum bits. So far, we have designed several basic SFQ cells, including wiring elements, flip-flops, and logic gates, using the four Nb planarized layer process and obtained the correct operation at 300 mK. In this study, we tested several SFQ circuits aiming to evaluate the operation at the mixing chamber stage of a dilution refrigerator. Our experimental results show that there was almost no change of device parameters, such as critical current values of Josephson junctions, or operating margins of the basic cells between 300 mK and 16 mK.

IEICE Transactions on ElectronicsApr 22, 20260 citations

Magnetic Cooling and Vibration Isolation of a Sub-kHz Mechanical Resonator

Bernard van Heck, Tim M. Fuchs, Jaimy Plugge +2 more

Abstract We report recent progress toward the realization of a sub-mK, low-vibration environment at the bottom stage of a dry dilution refrigerator for use in mechanical tests of quantum mechanics. Using adiabatic nuclear demagnetization, we have cooled a silicon cantilever force sensor to $T\approx 1$ T ≈ 1 mK. The temperature of the tip holder of the cantilever chip was determined via a primary magnetic flux noise thermometer. The quality factor of the cantilever continues to increase with decreasing temperature, reaching $Q\approx 4\cdot 10^4$ Q ≈ 4 · 10 4 at 2 mK. To demonstrate that the vibration isolation is not compromised, we report the detection of the thermal motion of the cantilever down to $T \approx 20$ T ≈ 20 mK, only limited by the coupling to the SQUID readout circuit. We discuss feasible improvements that will allow us to probe unexplored regions of the parameter space of continuous spontaneous localization models.Abstract We report recent progress toward the realization of a sub-mK, low-vibration environment at the bottom stage of a dry dilution refrigerator for use in mechanical tests of quantum mechanics. Using adiabatic nuclear demagnetization, we have cooled a silicon cantilever force sensor to $$T\approx 1$$ T ≈ 1 mK. The temperature of the tip holder of the cantilever chip was determined via a primary magnetic flux noise thermometer. The quality factor of the cantilever continues to increase with decreasing temperature, reaching $$Q\approx 4\cdot 10^4$$ Q ≈ 4 · 10 4 at 2 mK. To demonstrate that the vibration isolation is not compromised, we report the detection of the thermal motion of the cantilever down to $$T \approx 20$$ T ≈ 20 mK, only limited by the coupling to the SQUID readout circuit. We discuss feasible improvements that will allow us to probe unexplored regions of the parameter space of continuous spontaneous localization models.

arXiv:2208.11750Journal of Low Temperature PhysicsFeb 4, 20237 citations

\pm

2 mK for a dilution refrigerator base temperature of 18 mK.

T\approx 1

T ≈ 1 mK. The temperature of the tip holder of the cantilever chip was determined via a primary magnetic flux noise thermometer. The quality factor of the cantilever continues to increase with decreasing temperature, reaching

Q\approx 4\cdot 10^4

Q ≈ 4 · 10 4 at 2 mK. To demonstrate that the vibration isolation is not compromised, we report the detection of the thermal motion of the cantilever down to

T \approx 20

T ≈ 20 mK, only limited by the coupling to the SQUID readout circuit. We discuss feasible improvements that will allow us to probe unexplored regions of the parameter space of continuous spontaneous localization models.