Parallel Quantum Gates via Scalable Subsystem-Optimized Robust Control

TL;DR

This paper introduces a scalable control method for parallel quantum gates that reduces crosstalk errors by optimizing over small subsystems, significantly improving fidelity in large quantum processors.

Contribution

It presents a novel subsystem-optimized robust control approach that simplifies full-system optimization, enabling high-fidelity parallel gates without detailed crosstalk knowledge.

Findings

Reduces noise scaling from exponential to linear for single-qubit gates.

Achieves an order-of-magnitude error reduction for multi-qubit gates.

Validated across multiple quantum platforms with up to 200 qubits.

Abstract

Accurate and efficient implementation of parallel quantum gates is crucial for scalable quantum information processing. However, the unavoidable crosstalk between qubits in current noisy processors impedes the achievement of high gate fidelities and renders full Hilbert-space control optimization prohibitively difficult. Here, we overcome this challenge by reducing the full-system optimization to crosstalk-robust control over constant-sized subsystems, which dramatically reduces the computational cost. Our method effectively eliminates the leading-order gate operation deviations induced by crosstalk, thereby suppressing error rates. Within this framework, we construct analytical pulse solutions for parallel single-qubit gates and numerical pulses for parallel multi-qubit operations. We validate the proposed approach numerically across multiple platforms, including coupled nitrogen-vacancy centers, a nuclear-spin processor, and superconducting-qubit arrays with up to 200 qubits. As a result, the noise scaling is reduced from exponential to linear for parallel single-qubit gates, and an order-of-magnitude reduction is achieved for parallel multi-qubit gates. Moreover, our method does not require precise knowledge of crosstalk strengths and makes no assumption about the underlying qubit connectivity or lattice geometry, thereby establishing a scalable framework for parallel quantum control in large-scale quantum architectures.