Mitigating quantum decoherence via global optimal control

Superconducting quantum processors typically rely on local control lines for each qubit, which introduces significant wiring complexity, thermal noise, and cross-talk as systems scale. This paper explores an alternative: globally-driven architectures where a few shared control lines drive entire subsets of qubits. While this simplifies hardware, it raises concerns about robustness, as dissipation acts on all physical qubits—including those outside the logical register. The authors use tensor-network-based simulations to model a quasi-two-dimensional ladder geometry, quantifying how amplitude-damping and dephasing channels degrade quantum information flow and gate fidelity.

The researchers demonstrate that the impact of decoherence is not merely a result of local noise but is exacerbated by the disruption of the dynamical blockade mechanism that keeps the system in the computational subspace. By applying global optimal control, they shape the temporal profile of the driving pulses. This pulse optimization compresses the duration of gate sequences by an order of magnitude. By completing operations faster, the system spends less time exposed to environmental noise, effectively restoring high gate fidelities even in the presence of significant relaxation and dephasing rates.

This work provides a viable path toward scalable quantum computing by addressing the primary bottleneck of globally-driven architectures: their perceived fragility. By showing that temporal control can compensate for the lack of spatial addressing, the authors suggest that large-scale superconducting processors can be built with significantly simplified wiring without sacrificing the fidelity required for fault-tolerant operations. This approach turns a potential architectural weakness—the global nature of the drive—into a tool for active error mitigation.