@phdthesis{19533,
  abstract     = {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.
},
  author       = {Sett, Riya},
  issn         = {2663-337X},
  keywords     = {phase transition, open quantum system, phase diagram, cavity quantum electrodynamics, superconducting qubits, semiclassical physics, quantum optics, josephson junction, parametric converter, phase conjugation, quantum radar, quantum entanglement, correlation, quantum sensing},
  pages        = {109},
  publisher    = {Institute of Science and Technology Austria},
  title        = {{ Quantum remote sensing and non-equilibrium phase transitions in the microwave regime}},
  doi          = {10.15479/AT-ISTA-19533},
  year         = {2025},
}