Ultra-low power CryoCMOS RF multiplexer for qubit control at millikelvin temperatures

Scaling superconducting quantum computers to the millions of qubits needed for fault-tolerant operation requires overcoming the input-output bottleneck. Cryogenic multiplexers could be a scalable solution to address this large number of qubits. However, previous implementations required additional attenuation between the cryoCMOS chip and the qubits to suppress noise, making the multiplexing of costly output lines very challenging due to the extremely weak signals involved [1]. We report on a next-generation cryogenic CMOS RF multiplexer operating at 10 millikelvin, achieving ultra-low static power dissipation (100 pW), low insertion loss (< 3dB) and high isolation (> 30 dB) across the 0-10 GHz band. Crucially, we demonstrate direct connection to transmon qubits without attenuation, making the multiplexing of both the input and output lines feasible while preserving qubit coherence times exceeding 100 µs. Our results represent a key step toward scalable quantum-classical system co-integration, with potential to alleviate the input-output bottleneck in future large-scale quantum systems.



[1] Acharya et al., Nat. Electron. 6, 900 (2023).