DOI RECORD
Twisted superconducting quantum diodes for high fidelity anharmonic qubits
Abstract
Abstract In superconducting circuits, bidirectional signal propagation can cause back-reflections and back-action that couple environmental noise back to coherent elements, degrading fidelity. Nonreciprocal superconducting diodes provide an intrinsic route to suppress such back-scattering at the circuit level. However, their diode efficiency and quantum integration remain limited. Here, we realize a quantum diode in twisted NbSe 2 under in-plane and out-of-plane magnetic fields. A mere 1 ∘ twist yields an efficiency enhancement over pristine devices, reaching 27.6%. Quantum simulations reveal that this intermediate efficiency, well below 100% ideal, is both experimentally practical and optimal for preserving qubit anharmonicity and stabilizing two-level systems. These findings show that maximal rectification is not always beneficial for quantum information, establishing a new principle for designing the fundamental properties of twisted superconductors towards low-power, high-fidelity quantum circuits.