thesis published Riya Sett author 2E6D040E-F248-11E8-B48F-1D18A9856A870000-0001-7641-8348 Johannes M Fink supervisor GradSch department JoFi department Quantum readout techniques and technologies project QUANTUM INFORMATION SYSTEMS BEYOND CLASSICAL CAPABILITIES / P5- Integration of Superconducting Quantum Circuits project This thesis explores advancements in quantum remote sensing and non-equilibrium phase transitions in the microwave regime, with a focus on dissipative phase transitions and quantumenhanced sensing. In the first project, I experimentally studied photon blockade breakdown as a dissipative phase transition in a zero-dimensional cavity-qubit system. By defining an appropriate thermodynamic limit, we demonstrated that the observed bistability is a genuine signature of a first-order phase transition in this system. This work provides insight into non-equilibrium quantum dynamics and phase transitions in driven-dissipative open quantum systems. The second project focuses on the experimental realization of a phase-conjugate receiver for quantum illumination (QI), a quantum sensing protocol that enhances target detection in noisy environments using entangled light. While an ideal spontaneous parametric down-conversion (SPDC) source and receiver could, in theory, provide up to a 6 dB advantage over classical illumination, no such ideal receiver exists. Instead, we explore an experimental realization of a phase-conjugate receiver for QI in the microwave regime at millikelvin temperatures using a Josephson parametric converter (JPC) as a source of continuous-variable Gaussian entangled signal-idler pairs, where a maximum 3 dB advantage is theoretically achievable. We investigate key experimental limitations that constrain practical QI performance, contributing to the development of quantum-enhanced sensing. Additionally, this thesis presents efficient digital signal processing (DSP) techniques implemented in C++ and Python in collaboration with Przemysław Zieliński and Luka Drmić. These methods, optimized using the Intel Integrated Performance Primitives (IPP) library, have been essential in data acquisition, noise filtering, and correlation analysis across multiple research projects. Although not real-time, these DSP techniques significantly enhance the accuracy of quantum measurements. Overall, this thesis advances quantum-enhanced sensing by establishing the thermodynamic limit in a single transmon-cavity system and experimentally exploring a phase-conjugate receiver for QI. These findings contribute to quantum metrology, particularly for weak signal detection and remote sensing in noisy environments. https://research-explorer.ista.ac.at/download/19533/19538/PhD_Thesis_Riya_Sett_pdfa.pdf application/pdf2025-10-11no https://research-explorer.ista.ac.at/download/19533/19539/PhD Thesis Riya Sett.zip application/x-zip-compressed Institute of Science and Technology Austria2025 eng phase transitionopen quantum systemphase diagramcavity quantum electrodynamicssuperconducting qubitssemiclassical physicsquantum opticsjosephson junctionparametric converterphase conjugationquantum radarquantum entanglementcorrelationquantum sensing 2663-337X10.15479/AT-ISTA-19533 109 https://research-explorer.ista.ac.at/record/18978 https://research-explorer.ista.ac.at/record/19280 https://research-explorer.ista.ac.at/record/17183 https://research-explorer.ista.ac.at/record/13117 Sett R. 2025. Quantum remote sensing and non-equilibrium phase transitions in the microwave regime. Institute of Science and Technology Austria. R. Sett, Quantum Remote Sensing and Non-Equilibrium Phase Transitions in the Microwave Regime, Institute of Science and Technology Austria, 2025. Sett R. Quantum remote sensing and non-equilibrium phase transitions in the microwave regime. 2025. doi:<a href="https://doi.org/10.15479/AT-ISTA-19533">10.15479/AT-ISTA-19533</a> Sett, R. (2025). <i> Quantum remote sensing and non-equilibrium phase transitions in the microwave regime</i>. Institute of Science and Technology Austria. <a href="https://doi.org/10.15479/AT-ISTA-19533">https://doi.org/10.15479/AT-ISTA-19533</a> Sett, Riya. “ Quantum Remote Sensing and Non-Equilibrium Phase Transitions in the Microwave Regime.” Institute of Science and Technology Austria, 2025. <a href="https://doi.org/10.15479/AT-ISTA-19533">https://doi.org/10.15479/AT-ISTA-19533</a>. Sett, Riya. <i> Quantum Remote Sensing and Non-Equilibrium Phase Transitions in the Microwave Regime</i>. Institute of Science and Technology Austria, 2025, doi:<a href="https://doi.org/10.15479/AT-ISTA-19533">10.15479/AT-ISTA-19533</a>. R. Sett, “ Quantum remote sensing and non-equilibrium phase transitions in the microwave regime,” Institute of Science and Technology Austria, 2025. 195332025-04-09T16:44:26Z2026-06-03T07:16:05Z