Fluxonium Circuit Dynamics Under Periodic Drive: Insights for Quantum Computing

In a study published on April 30, 2025, Reparaz et al. conducted Landau-Zener-Stückelberg spectroscopy on fluxonium circuits, revealing resonance patterns that offer new insights into quantum dynamics and potential applications in advanced computing technologies.

The study investigates fluxonium circuits under large amplitude nonresonant periodic drives, analyzing time-averaged populations through numerical simulations that account for multi-level structures. Landau-Zener-Stückelberg spectra reveal resonances arising from constructive interference enhancing transitions to higher energy levels. For a two-level system, resonance patterns are explained via avoided crossings incorporating dynamic phases. In the multilevel case, an effective two-level Hamiltonian is derived using Schrieffer-Wolff transformations applied to the Floquet Hamiltonian in Sambe space. The research provides predictive insights into experimental outcomes and supports the development of fast non-adiabatic single-qubit gates.

In the realm of quantum mechanics, entanglement presents a phenomenon that defies classical understanding, where particles remain interconnected regardless of distance. This enigmatic feature is not merely theoretical; it holds transformative potential for technology. Recent advancements in superconducting qubits are illuminating new pathways to harness and manipulate entangled states, promising breakthroughs in computing, communication, and sensing.

At the forefront of this exploration lies Landau-Zener-Stückelberg (LZS) interferometry and Floquet engineering. LZS interferometry enables researchers to observe quantum transitions under periodic fields, revealing interference effects that offer insights into energy spectra and transition probabilities. Complementing this is Floquet engineering, which exploits time-periodic driving to simulate complex quantum phenomena, such as coherent backscattering, enhancing our understanding of entanglement dynamics.

Superconducting qubits, renowned for their high controllability with electromagnetic fields, form the backbone of these experiments. Coupled with microwave resonators, they allow precise control over driving fields that induce desired quantum states. By applying periodic microwave drives, researchers generate LZS spectra, elucidating intricate energy structures and facilitating the emulation of diverse quantum systems.

Research has revealed novel methods to stabilise and manipulate entangled states using periodic driving. Analysis of LZS spectra has identified parameters enhancing coherence, crucial for quantum computing stability. Additionally, Floquet engineering’s ability to simulate coherent backscattering opens new avenues for studying entanglement control in driven systems.

The implications extend beyond theory into practical applications. Enhanced entanglement control could lead to robust quantum computers, improved communication protocols, and advanced sensors. Moreover, the capacity to simulate complex phenomena using superconducting qubits provides a powerful tool for exploring fundamental quantum mechanics questions.