Active interference suppression in frequency-division-multiplexed quantum gates via off-resonant microwave tones

An increase in the number of control lines between the quantum processors and the external electronics constitutes a major bottleneck in the realization of large-scale quantum computers. Frequency-division multiplexing is expected to enable multiple qubits to be controlled through a single microwave cable; however, interference from off-resonant microwave tones hinders precise qubit control. Here, we propose an active interference suppression method for frequency-division-multiplexed simultaneous gate operations. We demonstrate that deliberate incorporation of off-resonant microwave tones improves the accuracy of single-qubit gates. Specifically, we find that by incorporating off-resonant orthogonal or quasi-orthogonal microwave tones, the gate infidelity decreases proportionally to the inverse square of the number of microwave tones. Furthermore, we show that fast oscillations neglected under the rotating wave approximation degrade gate fidelity, and that this degradation can be mitigated through optimized frequency allocation. Our approach is simple yet effective for improving the performance of frequency-division-multiplexed quantum gates.