One of the main thrusts of quantum science over the past few decades has been the development of quantum networks for the purposes of secure communication, enhanced detector sensitivity, and advanced computing. Realizing such a network of superconducting quantum processors that communicate via optical fibers would leverage the high fidelity quantum signal processing of superconducting circuits and the thermal robustness of infrared light but requires a transducer capable of connecting these two sections of the electromagnetic spectrum separated by five orders of magnitude in energy. This thesis explores the optimization of a transducer architecture where the mechanical mode of a Si3N4 membrane mediates the coupling of a superconducting lumpedelement circuit and a Fabry-Perot optical cavity. We aim to maximize the coupling of these three harmonic oscillator to each other while shielding them from noisy processes that would decohere quantum signals. This architecture has led to transducers with unparalleled efficiency and continuous operation. Enhanced cooperativity between the optical cavity and mechanical oscillator enabled optically-detected readout of a superconducting qubit and optomechanical ground state cooling with negligible laser-induced heating of the superconducting qubit and microwave circuit. To surpass the threshold for quantum-enabled operation, we subsequently improved the cooperativity between the microwave circuit and mechanical oscillator by reducing the microwave loss and noise from two-level-system-like defects in the Si3N4 dielectric. When combined with enhanced coupling between the circuit and membrane or improved mechanical isolation, we project that this architecture will be capable of transducing quantum signals between the microwave and optical regimes with a signal-to-noise greater than one.
BT - JILA and Department of Physics CY - Boulder N2 -One of the main thrusts of quantum science over the past few decades has been the development of quantum networks for the purposes of secure communication, enhanced detector sensitivity, and advanced computing. Realizing such a network of superconducting quantum processors that communicate via optical fibers would leverage the high fidelity quantum signal processing of superconducting circuits and the thermal robustness of infrared light but requires a transducer capable of connecting these two sections of the electromagnetic spectrum separated by five orders of magnitude in energy. This thesis explores the optimization of a transducer architecture where the mechanical mode of a Si3N4 membrane mediates the coupling of a superconducting lumpedelement circuit and a Fabry-Perot optical cavity. We aim to maximize the coupling of these three harmonic oscillator to each other while shielding them from noisy processes that would decohere quantum signals. This architecture has led to transducers with unparalleled efficiency and continuous operation. Enhanced cooperativity between the optical cavity and mechanical oscillator enabled optically-detected readout of a superconducting qubit and optomechanical ground state cooling with negligible laser-induced heating of the superconducting qubit and microwave circuit. To surpass the threshold for quantum-enabled operation, we subsequently improved the cooperativity between the microwave circuit and mechanical oscillator by reducing the microwave loss and noise from two-level-system-like defects in the Si3N4 dielectric. When combined with enhanced coupling between the circuit and membrane or improved mechanical isolation, we project that this architecture will be capable of transducing quantum signals between the microwave and optical regimes with a signal-to-noise greater than one.
PB - University of Colorado Boulder PP - Boulder PY - 2024 EP - 207 T2 - JILA and Department of Physics TI - Enhanced Cooperativity in a Near-Quantum Microwave-to-Optical Transducer VL - PhD ER -