Suppressing Spurious Transitions Using Spectrally Balanced Pulse

Achieving precise control over quantum systems presents a significant challenge, especially in many-body setups, where residual couplings and unintended transitions undermine the accuracy of quantum operations. In superconducting qubits, parasitic interactions-both between distant qubits and with spurious two-level systems-can severely limit the performance of quantum gates. In this Letter, we introduce a pulse-shaping technique that uses spectrally balanced microwave pulses to suppress undesired transitions. Experimental results demonstrate an order-of-magnitude reduction in spurious excitations between weakly detuned qubits as well as a substantial decrease in single-qubit gate errors caused by a strongly coupled two-level defect over a broad frequency range. Our method provides a simple yet powerful solution for mitigating adverse effects from parasitic couplings, enhancing quantum gate fidelity. The pulse-shaping technique can be readily adapted to various physical systems.