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Superconducting qubits in the millions: The potential and limitations of modularity

S.N. Saadatmand1,*, Tyler L. Wilson1, Mark J. Hodson1, Mark Field1, Simon J. Devitt2,3, Madhav Krishnan Vijayan3, Alan Robertson3, Thinh P. Le3, Jannis Ruh3 et al.

Alexandru Paler4,2, Arshpreet Singh Maan4,2, Ioana Moflic4,2, Athena Caesura5, and Josh Y. Mutus1

  • *Contact author: nsaadatmand@rigetti.com
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Phys. Rev. Applied 25, 064038 – Published 9 June, 2026

DOI: https://doi.org/10.1103/k3d5-v43c

Abstract

The development of fault-tolerant quantum computers (FTQCs) is receiving increasing attention within the quantum computing community. Like conventional digital computers, FTQCs, which utilize error correction and millions of physical qubits, have the potential to address some of humanity’s grand challenges. However, accurate estimates of the tangible scale of future FTQCs, based on transparent assumptions, are uncommon. How many physical qubits are necessary to solve a practical problem intractable for classical hardware? What costs arise from distributing quantum computation across multiple machines? This paper presents an architectural model of a potential FTQC based on superconducting qubits, divided into discrete modules and interconnected via coherent links. We employ a resource-estimation framework and software tool to assess the physical resources required to execute specific quantum algorithms compiled into their graph-state form and arranged onto a modular superconducting hardware architecture. Our tool can predict the size, power consumption, and execution time of these algorithms based on explicit assumptions about the physical layout, thermal load, and modular connectivity of the system. We assess the resources needed for quantum computation examples that serve as building blocks of proposed applications, quantifying the architectural bottlenecks and trade-offs that remain to be addressed to deliver utility.

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Corrections

29 June, 2026

Correction: Source information in Ref. [84] has been corrected.

Article Text

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Phys. Rev. Applied 25, 064038– Published 9 June, 2026
  • Received 11 August 2025
  • Revised 9 March 2026
  • Accepted 22 April 2026
  • Corrected 29 June 2026
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