arXiv subjects

Guillaume Bourcin

Publications and source records attributed to Guillaume Bourcin.

7 recordsLinked to original sources

arXiv2026

Multi-mode input-output model for cavity magnonics: phase-resolved control of level repulsion, level attraction, and nonreciprocal transmission

We experimentally validate a unified input--output model that incorporates internal and external coupling phases across multiple cavity modes in a room-temperature cavity magnonic system. By explicitly accounting for both phase contributions, the model provides a clear interpretation of the transition from level repulsion to level attraction at an interference-induced antiresonance, and accurately reproduces nonreciprocal transmission arising from the internal phases of the contributing modes. Quantitative agreement between experiments and simulations is obtained across all coupling regimes, establishing a predictive framework for phase-controlled cavity--magnon devices including isolators, circulators, and quantum transducers.

quant-ph↗

arXiv2025

Controllable Non-reciprocity in Multi-sphere Loaded Chiral Resonator

Cavity magnonics explores the hybridization of photons and magnons within microwave resonators. One of the hallmarks of these systems is their ability to exhibit non-reciprocity, which is a key feature for radio frequency (RF) applications. One way to control non-reciprocal behaviors in cavity magnonics is the design of chiral cavities that allow selective coupling between photons and magnons depending on their polarization. However, a built-in chiral platform to harness and control non-reciprocity remains to be achieved. Here, we experimentally demonstrate controllable non-reciprocity (with an absolute isolation ratio reaching 46 dB) in a chiral resonator loaded with multiple yttrium iron garnet spheres. We develop a theoretical model of the S-parameters based on input-output formalism which highlights the links between the phases occurring in the system and its non-reciprocal behavior. Controllable non-reciprocity in cavity magnonics could enable the development of programmable isolators, circulators, and RF switches with improved performance. Such developments could pave the way toward more versatile and scalable information processing systems.

cond-mat.mtrl-sci↗

arXiv2024

Level attraction from interference in two-tone driving

Coherent and dissipative couplings, respectively characterised by energy level repulsion and attraction, each have different applications for quantum information processing. Thus, a system in which both coherent and dissipative couplings are tunable on-demand and in-situ is tantalising. A first step towards this goal is the two-tone driving of two bosonic modes, whose experimental signature was shown to exhibit controllable level repulsion and attraction by changing the phase and amplitude of one drive. However, whether the underlying physics is that of coherent and dissipative couplings has not been clarified, and cannot be concluded solely from the measured resonances (or anti-resonances) of the system. Here, we show how the physics at play can be analysed theoretically. Combining this theory with realistic finite-element simulations, we deduce that the observation of level attraction originates from interferences due to the measurement setup, and not dissipative coupling. Beyond the clarification of a novel origin for level attraction attributed to interference, our work demonstrate how effective Hamiltonians can be derived to appropriately describe the physics.

quant-ph↗

arXiv2024

Engineering synthetic gauge fields through the coupling phases in cavity magnonics

Cavity magnonics, which studies the interaction of light with magnetic systems in a cavity, is a promising platform for quantum transducers and quantum memories. At microwave frequencies, the coupling between a cavity photon and a magnon, the quasi-particle of a spin wave excitation, is a consequence of the Zeeman interaction between the cavity's magnetic field and the magnet's macroscopic spin. For each photon/magnon interaction, a coupling phase factor exists, but is often neglected in simple systems. However, in "loop-coupled" systems, where there are at least as many couplings as modes, the coupling phases become relevant for the physics and lead to synthetic gauge fields. We present experimental evidence of the existence of such coupling phases by considering two spheres made of Yttrium-Iron-Garnet and two different re-entrant cavities. We predict numerically the values of the coupling phases, and we find good agreement between theory and the experimental data. These results show that in cavity magnonics, one can engineer synthetic gauge fields, which can be useful for cavity-mediated coupling and engineering dark mode physics.

quant-ph↗

arXiv2024

Level attraction in a quasi-closed cavity

We provide a comprehensive analytical description of the effective coupling associated with an antiresonance within a hybrid system comprised of a quasi-closed photonic cavity and a ferrimagnetic material. Whilst so-called level attraction between a resonant system inside an open cavity is well understood, the physical underpinnings of this phenomena within quasi-closed cavities have remained elusive. Leveraging the input-output theory, we successfully differentiate between the repulsive and attractive aspects of this coupling. Our proposed model demonstrates that by understanding the phase-jump at the resonances and the studied antiresonance, we can predict the nature of the effective coupling of the antiresonance for a given position of the ferrimagnet in the cavity.

quant-ph↗

arXiv2023

Static and dynamic magnetization control of extrinsic multiferroics by the converse magneto-photostrictive effect

In this work, photostrictive manipulations of static and dynamic magnetic properties are demonstrated in an extrinsic multiferroic composite. The photostriction is achieved with visible light in the blue region of the spectrum. The composites consist of 5 nm or 10 nm magnetostrictive Fe$_{81}$Ga$_{19}$ thin films coupled to a piezoelectric (011)-Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_3$-Pb(Zr,Ti)O$_3$ substrate. Angular dependent magnetization reversals properties are largely enhanced or reduced under a converse magneto-photostrictive effect (CMPE). The CMPE strength is analysed with a novel coefficient named the converse magneto-photostrictive coupling coefficient. This coefficient is proposed as a general approach to analyse and to compare different extrinsic multiferroics under the converse magneto-photostrictive effect. Its thickness dependence reveals that the CMPE strength decreases with an increase of the Fe$_{81}$Ga$_{19}$ thickness. Experimental evidence for a control of dynamic magnetic properties under CMPE is then revealed by ferromagnetic resonance measurements. Resonant fields are shifted under CMPE, whereas their linewidths remain constant. Furthermore, resonant field shifts can be either positive or negative depending on the in-plane angle. The largest shift under CMPE of +5.7 % is obtained for the 5 nm sample. Our study shows that the CMPE provides an efficient approach for a control of not only the static but also the dynamic magnetic properties in extrinsic multiferroics.

cond-mat.mes-hall↗

arXiv2023

Strong to ultra-strong coherent coupling measurements in a YIG/cavity system at room temperature

We present an experimental study of the strong to ultra-strong coupling regimes at room temperature in frequency-reconfigurable 3D re-entrant cavities coupled with a YIG slab. The observed coupling rate, defined as the ratio of the coupling strength to the cavity frequency of interest, ranges from 12% to 59%. We show that certain considerations must be taken into account when analyzing the polaritonic branches of a cavity spintronic device where the RF field is highly focused in the magnetic material. Our observations are in excellent agreement with electromagnetic finite element simulations in the frequency domain.

quant-ph↗