Multi-qubit Dynamical Decoupling for Enhanced Crosstalk Suppression

Dynamical decoupling (DD) is one of the simplest error suppression methods,aiming to enhance the coherence of qubits in open quantum systems. Moreover, DDhas demonstrated effectiveness in reducing coherent crosstalk, one major errorsource in near-term quantum hardware, which manifests from two types ofinteractions. Static crosstalk exists in various hardware platforms, includingsuperconductor and semiconductor qubits, by virtue of always-on qubit-qubitcoupling. Additionally, driven crosstalk may occur as an unwanted drive termdue to leakage from driven gates on other qubits. Here we explore a novelstaggered DD protocol tailored for multi-qubit systems that suppresses thedecoherence error and both types of coherent crosstalk. We develop twoexperimental setups - an "idle-idle" experiment in which two pairs of qubitsundergo free evolution simultaneously and a "driven-idle" experiment in whichone pair is continuously driven during the free evolution of the other pair.These experiments are performed on an IBM Quantum superconducting processor anddemonstrate the significant impact of the staggered DD protocol in suppressingboth types of coherent crosstalk. When compared to the standard DD sequencesfrom state-of-the-art methodologies with the application of X2 sequences, ourstaggered DD protocol enhances circuit fidelity by 16.9respectively, in addressing these two crosstalk types.