Exploration and Analysis of Metallic, Optical, and Superconducting Cryo-Interconnects for Large-Scale Quantum Computers

Determining optimal interconnect solutions is crucial to realize high-performance and energy-efficient large scale quantum computers (QC). This work presents the first comprehensive exploration and analysis of a wide range of interconnect technologies under cryogenic conditions. We determine the best on-chip interconnect materials for cryogenic interface electronics (CIE) based on required current density and wire geometry among metals, doped-multilayer-graphene (DMLG), as well as superconductors, and, subsequently, evaluate various transistor and interconnect technology combinations for CIE. This is followed by analyzing the heat loads across system-level interconnects (or cables) used to transmit signals across different temperature zones in the dilution refrigerator. Our results indicate that optical-fiber cables are key to realizing large-scale QC beyond 10³ qubits.