Speaker
Description
Quantum magnonics explores magnons—quasiparticles of spin waves—as carriers of quantum information, enabling coherent coupling to superconducting qubits and single-magnon detection [1,2]. Yttrium iron garnet (YIG) remains the material of choice due to its exceptionally low magnetic damping; however, magnon lifetimes at GHz frequencies are typically limited to ~1 μs for the uniform ferromagnetic resonance mode, constraining coherent quantum applications [3]. Here, we demonstrate record-long magnon lifetimes in the quantum limit (T → 0), exceeding 18 μs at 1.6 GHz for short-wavelength dipolar-exchange magnons in an ultra-pure single-crystal YIG sphere at millikelvin temperatures [4]. Lifetimes were extracted using broadband ferromagnetic resonance spectroscopy combined with measurements of the three-magnon parametric instability threshold, giving direct access to short-wavelength magnon relaxation rates inaccessible by conventional means. The results reveal strong suppression of multi-magnon and magnon–phonon scattering in the quantum regime. Compared to the uniform mode, short-wavelength magnons exhibit reduced sensitivity to surface defects and lattice imperfections, enabling substantially longer lifetimes. At the lowest temperatures, all extrinsic relaxation channels are frozen out, and the lifetime becomes governed solely by intrinsic material purity. The observed 18 μs lifetime sets a new benchmark for magnetic coherence, placing magnons on a timescale comparable to superconducting qubits and opening a pathway toward hybrid solid-state quantum networks [3].
[1] D. Lachance-Quirion, S. P. Wolski, Y. Tabuchi, et al., Science 367,
425 (2020).
[2] D. Xu, X.-K. Gu, H.-K. Li, et al., Phys. Rev. Lett. 130, 193603
(2023).
[3] R. O. Serha, C. Dubs, A. V. Chumak, APL Materials 14, 030401 (2026).
[4] R. O. Serha, K. H. McAllister, F. Majcen, et al., arXiv:2505.22773 (2025).