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Unit Fidelity Entangling Gates Achieved Via Continuous Dynamical Decoupling and Optimal Control

Researchers at the São Carlos Institute of Physics have combined continuous dynamical decoupling (CDD) with variational minimal‑energy optimal control to create two‑qubit entangling gates with virtually unit fidelity. The unified scheme actively suppresses low‑frequency flux noise, calibration drift, and spurious couplings, stabilising the effective Hamiltonian for tunable CZ and CX operations. By employing a variational geodesic optimisation that solves a nonlinear Schrödinger equation, the team eliminates the need for complex pulse‑shaping or neural‑network methods. Simulations on superconducting transmons show robust, high‑fidelity performance using experimentally realistic control fields.