Quantum networks with time-delays and high-impedance transmission lines

Research Project, 2022 – 2025

This proposal concerns the theoretical analysis of superconducting quantum networks consisting of one-dimensional waveguides for microwave photons or phonons, interacting with one or more superconducting artificial atoms. In this field of Waveguide Quantum Electrodynamics (WQED), we want to analyze the situation with many excitations and finite time-delays, using a newly developed formalism based on matrix product states.
In addition, we want to extend the analysis of superconducting artificial atoms coupled to high impedance transmission lines, which have recently become experimentally accessible. The speed of light in these transmission lines can be more than two orders of magnitude slower than in vacuum, which implies that time delays become important for smaller systems.High impedance transmission lines enable coupling the artificial atom so strongly that its lifetime approaches its oscillation period. In this regime, matrix product states are also useful to analyze the dynamics.The main driving force behind this project is curiosity. It is however not impossible that the insights from this project can have impact on future versions of architectures for superconducting quantum information processors. At the moment, they do not include high-impedance transmission lines, nor delay lines, but we aim at understanding whether this could be advantageous in the future, since there are novel schemes for photonic quantum computation relying on coherent time delays.