Identify the hardware modality best suited for large-scale, problem-solving quantum computers

Determine which quantum computing hardware modalities—such as superconducting circuits, trapped ions, neutral Rydberg atoms, photonic qubits, or spin qubits—are best suited to scale to large systems that can solve computationally hard problems, taking into account connectivity, gate fidelities, cycle times, error-correction overheads, and architectural constraints.

Background

The paper reviews rapid advances across leading modalities (superconducting circuits, trapped ions, neutral atoms) and highlights that each has distinct strengths and weaknesses in connectivity, speed, and practicality of syndrome extraction and logical operations.

Despite recent milestones in error correction and demonstrations of logical circuits, the authors stress that the landscape is still shifting and that modalities previously considered less promising (e.g., Rydberg arrays) have emerged strongly, making it premature to declare a dominant path to broadly useful fault-tolerant machines.

References

We do not know yet which quantum computing modalities will be best suited for scaling to large systems that solve hard problems.

— Mind the gaps: The fraught road to quantum advantage  (2510.19928 - Eisert et al., 22 Oct 2025) in Section 3: From protected quantum memory to scalable fault-tolerant quantum computation (tcolorbox)

Whether this milestone will be achieved first via a CV cluster state leveraging GKP encoding, a DV protocol utilizing fusion gates and percolation theory, or an entirely novel hybrid approach, remains an open question.

— Optical Quantum Computing  (2609.18347 - Hasnaoui et al., 16 Sep 2026) in Section “Conclusions and Perspectives”

What remains unclear is how much reliability is gained by moving beyond the lower bound, and how that gain trades off against quantum error correction (QEC) absorption and compiler makespan.

— Beyond Legal Spacing: A Residual-Aware Characterization of Entangling-Zone Spacing in Neutral-Atom Compilation  (2608.17331 - Li et al., 18 Aug 2026) in Section 1, Introduction

Fault-tolerant quantum computing requires not only reliable logical qubit storage, but also the ability to perform high-fidelity logical operations between error-corrected qubits at scale. While much of the existing literature focuses on optimizing syndrome extraction for a single logical qubit, the co-design of physical architectures that support both robust error correction and efficient logical computation remains an open challenge.

— Transversal Gates and Magic State Distillation in an Optimally Synthesized Spin-Qubit Shuttling Bus  (2609.02641 - Escofet et al., 2 Sep 2026) in Abstract

Whether such constructions can be implemented efficiently on neutral-atom hardware, and what architectural advantages 3D would provide in that setting, remain open questions.

— Efficient Quantum Error Correction from Three Dimensional Qubit Control  (2609.04459 - Wu et al., 3 Sep 2026) in Conclusion