Minimal-Energy Optimal Control of Tunable Two-Qubit Gates in Superconducting Platforms Using Continuous Dynamical Decoupling

TL;DR

This paper introduces a noise-resilient method combining continuous dynamical decoupling and variational optimal control to achieve high-fidelity, tunable two-qubit gates in superconducting quantum systems.

Contribution

It develops a unified scheme that suppresses noise and residual couplings, enabling the design of high-fidelity entangling gates with minimal energy using geometric optimization.

Findings

Achieved virtually unit fidelity for CZ, CX, and generic entangling gates.

Demonstrated robustness under realistic control constraints.

Established a practical scheme for noise-resilient superconducting gates.

Abstract

We present a unified scheme for generating high-fidelity entangling gates in superconducting platforms by continuous dynamical decoupling (CDD) combined with variational minimal-energy optimal control. During the CDD stage, we suppress residual couplings, calibration drifting, and quasistatic noise, resulting in a stable effective Hamiltonian that preserves the designed ZZ interaction intended for producing tunable couplers. In this stable $\mathrm{SU}(4)$ manifold, we calculate smooth low-energy single-quibt control functions using a variational geodesic optimization process that directly minimizes gate infidelity. We illustrate the methodology by applying it to CZ, CX, and generic engangling gates, achieving virtually unit fidelity and robustness under restricted single-qubit action, with experimentally realistic control fields. These results establish CDD-enhanced variational geometric optimal control as a practical and noise-resilient scheme for designing superconducting entangling gates.