Leakage Suppression in Quantum Control via Static Parameter Offsets

TL;DR

This paper introduces a simple, static offset method to suppress leakage errors in quantum control, improving fidelity without extra pulses or complex optimization, validated on superconducting circuits.

Contribution

It presents a novel static parameter offset strategy for leakage suppression that is compatible with existing control frameworks and enhances quantum gate fidelity.

Findings

Effective leakage suppression demonstrated in superconducting circuits.

Enables high-fidelity single-qubit and two-qubit operations.

Supports integration with optimal control for combined error mitigation.

Abstract

High-fidelity quantum operations require the system dynamics to be strictly confined to the computational subspace. In practice, however, control fields inevitably couple to leakage levels, giving rise to quantum state leakage that significantly reduces the fidelity of the operation. To address this challenge, we propose a general strategy for actively suppressing leakage errors by applying small, static offsets to tunable system parameters. This approach systematically mitigates leakage's detrimental impact on quantum control, without modifying the original control framework or incurring additional time overhead. By avoiding the need for extra suppression pulses or complex optimization procedures altogether, it offers a streamlined solution for leakage compensation while remaining fully compatible with subsequent optimal control techniques. Numerical validation conducted on superconducting quantum circuits demonstrates effective leakage suppression, enabling high-fidelity single-qubit gates, precise control of two-qubit interactions, and perfect state transfer in multi-level systems. Moreover, when integrated with optimal control techniques, our approach also allows for the cooperative suppression of both leakage errors and residual crosstalk. Therefore, this work provides a feasible technical pathway toward the low error thresholds required for fault-tolerant quantum computation.