Ingress Cryogenic Receivers Toward Scalable Quantum Information Processing: Theory and System Analysis

Current control techniques for cryogenically cooled qubits are realized with coaxial cables, posing multiple challenges in terms of cost, thermal load, size, and long-term scalability. Emerging approaches to tackle this issue include cryogenic CMOS electronics at 4 K, and photonic links for direct qubit control. In this paper, we propose a multiplexed all-passive cryogenic high frequency direct detection control platform (cryo-HFDD). The proposed classical interface for direct qubit control utilizes optical or sub-THz bands. We present the possible tradeoffs of this platform, and compare it with current state-of-the-art cryogenic CMOS and conventional coaxial approaches. We assess the feasibility of adopting these efficient links for a wide range of microwave qubit power levels. Specifically, we estimate the heat load to achieve the required signal-to-noise ratio SNR considering different noise sources, component losses, as well as link density. We show that multiplexed photonic receivers at 4 K can aggressively scale the control of thousands of qubits. This opens the door for low cost scalable quantum computing systems.