TY - BOOK

T1 - Exploiting quantum paraelectricity for advancing cryogenic quantum measurements

AU - Das, Deepanjan

PY - 2025

Y1 - 2025

N2 - Over a few decades, superconducting quantum devices have been at the forefront of many advanced research and technologies in various disciplines such as quantum computing and communication, high precision measurements, quantum information processing and metrology, quantum sensing, detection techniques, and so on. Although there has always been continuous endeavour to improve the readout signal from these sensitive quantum devices, there are still many issues to be solved. Signal power loss due to impedance mismatch along the readout line is one of them. Another is that a very weak signal always requires amplification with least thermal noise to be detected at room temperature equipment. Therefore, developing a novel ultra-low noise cryogenic amplifier which can work in the presence of a strong magnetic field, would be beneficial in advancing existing cryo-measurement setups.The work presented in this thesis explores the potential of quantum paraelectricity to improve the quality of radio-frequency (rf) and microwave measurements at low temperatures. The quantum paraelectricity has been studied by characterising an on-chip variable capacitor on top of a quantum paraelectric material (i.e. strontium titanate and potassium tantalate). The initial study gives us an overview of its dielectric nature in the presence of an external electric field in a cryogenic environment (∼ 10 mK). After that, the material has been used to develop a lumped element based impedance matching network that can be incorporated into a readout line for rf and microwave measurements in a dry dilution refrigerator. The inherent non-linearity has also been exploited through wave mixing techniques in order to discover its ability towards parametric amplification.

AB - Over a few decades, superconducting quantum devices have been at the forefront of many advanced research and technologies in various disciplines such as quantum computing and communication, high precision measurements, quantum information processing and metrology, quantum sensing, detection techniques, and so on. Although there has always been continuous endeavour to improve the readout signal from these sensitive quantum devices, there are still many issues to be solved. Signal power loss due to impedance mismatch along the readout line is one of them. Another is that a very weak signal always requires amplification with least thermal noise to be detected at room temperature equipment. Therefore, developing a novel ultra-low noise cryogenic amplifier which can work in the presence of a strong magnetic field, would be beneficial in advancing existing cryo-measurement setups.The work presented in this thesis explores the potential of quantum paraelectricity to improve the quality of radio-frequency (rf) and microwave measurements at low temperatures. The quantum paraelectricity has been studied by characterising an on-chip variable capacitor on top of a quantum paraelectric material (i.e. strontium titanate and potassium tantalate). The initial study gives us an overview of its dielectric nature in the presence of an external electric field in a cryogenic environment (∼ 10 mK). After that, the material has been used to develop a lumped element based impedance matching network that can be incorporated into a readout line for rf and microwave measurements in a dry dilution refrigerator. The inherent non-linearity has also been exploited through wave mixing techniques in order to discover its ability towards parametric amplification.

U2 - 10.17635/lancaster/thesis/2846

DO - 10.17635/lancaster/thesis/2846

M3 - Doctoral Thesis

PB - Lancaster University

ER -