Performance Evaluation of a RISC-V CPU at Cryogenic Temperature for Future Quantum Control

Cryogenic CMOS is garnering lots of attentions as promising solutions for future large scale quantum computers. However, most of recent works focus on improving the analog front-end to enhance qubit drive and read-out fidelity, leveraging on simple customized digital control. We anticipate that future practical quantum control system-on-chip (SoC) will require full-fledged general purpose processors operating at cryogenic temperature to enable flexibility and programmability when running quantum applications. To advance this vision, this work reports a 32-bit RISC-V central processing unit fabricated using a ultra-low threshold voltage 28nm CMOS process. Our tests showed that even with standard digital implementation flow, the chip is fully functional at temperature of 77K with similar power per MHz as compared to at room temperature (i.e. 300K), while consuming ∼300× less leakage power. This paves an important ground work towards a RISC-V based SoC for large scale quantum computing applications at 4K temperature.