Superconducting qubits at elevated frequencies

Quantum processors based on superconducting qubits typically operate in the 4-8 GHz range, where materials, control electronics, and microwave components are well optimized. Increasing the qubit transition frequency beyond this range (up to 20 GHz) is expected to offer several advantages, including lower thermal excited-state population, enhanced anharmonicities and prospects for operation at warmer cryogenic stages compatible with cryo-CMOS control. However, higher frequencies can amplify losses from junction metals and dielectric interfaces, tighten Purcell constraints, and increase coupling to parasitic modes.

In this work, we outline recent progress toward enabling robust high-frequency operation of superconducting qubits. Our aim is to investigate the design and implementation of superconducting qubits and resonators operating in an elevated frequency regime while analyzing how key device parameters (such as junction design, material choice, and resonator coupling) affect coherence and anharmonicity in this regime. The goal is to identify limiting loss mechanisms and develop design strategies that could enable robust, high-frequency qubit operation suitable for next-generation quantum processors.