Phase-sensitive detection with the Radio-Frequency Quantum Upconverter
ORAL
Abstract
The Radio-Frequency Quantum Upconverter (RQU) is a superconducting frequency upconverter designed to meet the need for better precision electromagnetic measurements at low frequencies. An RQU consists of a Josephson-junction interferometer embedded in a superconducting microwave resonator, and for small signals at MHz frequency, the interferometer presents a tunable inductance to the microwave circuit, creating a parametric interaction between the signal-frequency flux and the microwave mode. The upconverted signal appears as sidebands of the microwave carrier tone. RQUs with a three-junction interferometer design enable clean implementation of quantum upconversion protocols including sideband cooling, two-mode squeezing, and backaction-evading (BAE) detection. We discuss measurements with prototype RQUs, including phase-sensitive detection of a low frequency circuit which is a necessary prerequisite for evading quantum backaction noise. Additionally, we discuss BAE protocol applications in high-precision electromagnetic measurements including sub-μeV axion searches.
*This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, QuantISED program under FWP 100495. We would also like to acknowledge the Stanford Nanofabrication Facility and Safavi-Naeini group for providing facilities and guidance for this project.
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Presenters
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Elizabeth C van Assendelft
- Stanford University