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Integration and Resource Estimation of Cryoelectronics for Superconducting Fault-Tolerant Quantum Computers

Shiro Kawabata

TL;DR

This work addresses the engineering challenge of scaling superconducting fault-tolerant quantum computers by examining the integration of cryogenic electronics with quantum processors. It proposes a first-order accounting framework that connects qubit counts to stage-wise power budgets and wiring constraints, enabling principled comparisons across room-temperature racks, cryo-CMOS at 4 K, and superconducting logic at mK stages. By anchoring the discussion to RSA-2048 factoring as a concrete benchmark, the paper highlights the required modularization, multiplexing, and cross-layer co-design needed to reach future FTQC scales. The key contribution is a systems-level perspective that identifies heterogeneous integration—combining room-temperature control with cryo-CMOS, SFQ, and AQFP elements—as essential to balancing bandwidth, latency, heat load, and qubit compatibility. The findings inform architecture choices and resource planning for large-scale quantum computers, while pointing to complementary interconnect approaches such as photonics and wireless links to further mitigate wiring and thermal loads.

Abstract

Scaling superconducting quantum computers to the fault-tolerant regime calls for a commensurate scaling of the classical control and readout stack. Today's systems largely rely on room-temperature, rack-based instrumentation connected to dilution-refrigerator cryostats through many coaxial cables. Looking ahead, superconducting fault-tolerant quantum computers (FTQCs) will likely adopt a heterogeneous quantum-classical architecture that places selected electronics at cryogenic stages -- for example, cryo-CMOS at 4~K and superconducting digital logic at 4~K and/or mK stages -- to curb wiring and thermal-load overheads. This review distills key requirements, surveys representative room-temperature and cryogenic approaches, and provides a transparent first-order accounting framework for cryoelectronics. Using an RSA-2048-scale benchmark as a concrete reference point, we illustrate how scaling targets motivate constraints on multiplexing and stage-wise cryogenic power, and discuss implications for functional partitioning across room-temperature electronics, cryo-CMOS, and superconducting logic.

Integration and Resource Estimation of Cryoelectronics for Superconducting Fault-Tolerant Quantum Computers

TL;DR

This work addresses the engineering challenge of scaling superconducting fault-tolerant quantum computers by examining the integration of cryogenic electronics with quantum processors. It proposes a first-order accounting framework that connects qubit counts to stage-wise power budgets and wiring constraints, enabling principled comparisons across room-temperature racks, cryo-CMOS at 4 K, and superconducting logic at mK stages. By anchoring the discussion to RSA-2048 factoring as a concrete benchmark, the paper highlights the required modularization, multiplexing, and cross-layer co-design needed to reach future FTQC scales. The key contribution is a systems-level perspective that identifies heterogeneous integration—combining room-temperature control with cryo-CMOS, SFQ, and AQFP elements—as essential to balancing bandwidth, latency, heat load, and qubit compatibility. The findings inform architecture choices and resource planning for large-scale quantum computers, while pointing to complementary interconnect approaches such as photonics and wireless links to further mitigate wiring and thermal loads.

Abstract

Scaling superconducting quantum computers to the fault-tolerant regime calls for a commensurate scaling of the classical control and readout stack. Today's systems largely rely on room-temperature, rack-based instrumentation connected to dilution-refrigerator cryostats through many coaxial cables. Looking ahead, superconducting fault-tolerant quantum computers (FTQCs) will likely adopt a heterogeneous quantum-classical architecture that places selected electronics at cryogenic stages -- for example, cryo-CMOS at 4~K and superconducting digital logic at 4~K and/or mK stages -- to curb wiring and thermal-load overheads. This review distills key requirements, surveys representative room-temperature and cryogenic approaches, and provides a transparent first-order accounting framework for cryoelectronics. Using an RSA-2048-scale benchmark as a concrete reference point, we illustrate how scaling targets motivate constraints on multiplexing and stage-wise cryogenic power, and discuss implications for functional partitioning across room-temperature electronics, cryo-CMOS, and superconducting logic.
Paper Structure (13 sections, 1 equation, 3 figures, 1 table)

This paper contains 13 sections, 1 equation, 3 figures, 1 table.

Table of Contents

  1. Introduction
  2. Requirements for Cryoelectronics
  3. Fault-tolerant Quantum Computers
  4. Constraints on Power and Interconnect Density
  5. Current Approaches
  6. Room-Temperature Rack-Based Systems
  7. Cryo-CMOS
  8. Superconducting Digital Logic
  9. Toward Scalable FTQCs
  10. Target scale and modularization
  11. Power budget at scale
  12. Implications for functional partitioning
  13. Summary and Perspectives

Figures (3)

  • Figure 1: Conceptual comparison of the control/readout stack for superconducting FTQCs: (a) a conventional room-temperature, rack-based setup with extensive coaxial wiring to the cryostat; (b) a future heterogeneous stack that integrates cryogenic electronics---e.g., cryogenic CMOS (cryo-CMOS) at 4 K and superconducting digital logic, i.e., single-flux-quantum (SFQ) at 4 K and adiabatic quantum-flux-parametron (AQFP) at the 10 mK stage---to reduce wiring overhead and shorten feedback latency. Placement is schematic; actual implementations may distribute functions across 4K/1K/100mK/10mK stages and still require non-negligible cryogenic interconnects.
  • Figure 2: Power per refrigerator at stage $T$, $P_{T}^{(\mathrm{fridge})}=N_{\mathrm{phys}}^{(\mathrm{fridge})}P_{\mathrm{phys}}^{(T)}/M$, as a function of the effective multiplexing factor $M$ for $N_{\mathrm{phys}}^{(\mathrm{fridge})}=10^4$. Solid curves compare representative per-physical-qubit dissipation values for cryo-CMOS and superconducting digital logic (SFQ and AQFP) taken from the literature Bardin2019vanDijk2020Takeuchi2024. Dash-dotted lines (4 K) and dotted lines (10--20 mK) indicate example cooling-power budgets for the XLD1000sl and Fermilab Colossus platforms BlueforsXLD1000slHollister2024Colossus.
  • Figure 3: An illustrative example of functional partitioning between room-temperature electronics and cryo-electronics in a dilution refrigerator for large-scale superconducting FTQCs. Placement is schematic and may vary by technology and system constraints.