Background:
Superconducting fluxonium circuits have recently emerged as a compelling platform for exploring qudits—quantum systems with more than two accessible levels. Their large anharmonicity, rich energy spectrum, and reduced sensitivity to charge noise make them particularly well-suited for coherent control of higher excited states. Leveraging these properties opens up new possibilities for quantum information processing, including more efficient encodings, reduced gate counts, and novel algorithmic primitives.
While qubits based on transmons have been widely studied, the systematic use of higher levels in fluxoniums remains relatively unexplored, both theoretically and experimentally. In particular, understanding the detailed structure of the higher excited states, their transition strengths, and decoherence mechanisms is essential for building reliable single- and multi-qudit gates. Experimentally, precise control of these transitions requires tailored pulse schemes, with Rabi processes playing a central role in implementing arbitrary single-qudit operations.
Tasks:
The project comprises two parts:
Theory and Spectral Analysis of Fluxonium Qudits
Learn the theoretical models of fluxonium devices that captures the higher excited states relevant for qudit operation. Calculate energy spectra, transition frequencies, and matrix elements between states, including selection rules.
Experimental Control and Rabi Gate Implementation
Design and implement experimental pulse sequences to drive Rabi oscillations between selected levels beyond the computational qubit manifold. Characterize coherence times and leakage rates for higher-level transitions. Demonstrate single-qudit gates by calibrating and benchmarking Rabi processes for arbitrary state-to-state control.
Outcome:
The project will produce a comprehensive theoretical and experimental characterization of fluxonium-based qudits. The results will lay the groundwork for extending the control framework to multi-qudit systems and for integrating fluxonium qudits into more complex quantum computing architectures.
