Superconducting qubits with quantum non-demolition readout and active feedback can act as information engines to probe and control microscopic degrees of freedom, both engineered and environmental. However, performing such experiments in magnetic fields above tens of mT poses a significant challenge for conventional superconducting qubits. We demonstrate a fluxonium qubit with a granular aluminum nanojunction (gralmonium) that maintains spectral stability and coherence above 1 T [1]. This robust performance enables exploration of spin environment dynamics and supports hybrid quantum architectures integrating superconducting qubits with spin systems [2].
[1] Günzler & Beck et al., Nature Comm. 16, 9564 (2025)
[2] Günzler et al., Phys. Rev. B 112, 115424 (2025)