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arxiv: 2511.13657 · v1 · pith:KZHPXHFOnew · submitted 2025-11-17 · 🪐 quant-ph

Architectural Approaches to Fault-Tolerant Distributed Quantum Computing and Their Entanglement Overheads

Nitish Kumar Chandra , Eneet Kaur , Kaushik P. Seshadreesan This is my paper

Pith reviewed 2026-05-17 21:48 UTC · model grok-4.3

classification 🪐 quant-ph
keywords fault-tolerant distributed quantum computingarchitectural typessurface codetoric codeBell pairsentanglement overheadcode distance scalingGHZ states
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The pith

Different architectures for fault-tolerant distributed quantum computing show distinct scaling of Bell pair requirements with code distance.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper identifies three main architectural approaches to fault-tolerant distributed quantum computing. Type 1 connects small nodes using GHZ states for nonlocal stabilizer measurements. Type 2 distributes parts of a large code block across modules, keeping most stabilizers local. Type 3 places complete code blocks in separate modules and performs logical operations via transversal gates or lattice surgery. For the planar surface code and toric code, it compares how the number of needed Bell pairs and the average generation attempts grow as the code distance increases. This comparison matters for determining which designs can operate within the entanglement production limits of current and near-future quantum devices.

Core claim

Using planar surface and toric codes, the number of Bell pairs and average generation attempts required for fault-tolerant operations scale with code distance in ways that depend on the chosen architectural type among the three categories.

What carries the argument

The categorization into three architectural types and the subsequent scaling analysis of entanglement resources with code distance.

Load-bearing premise

The three-type categorization captures the dominant practical approaches and the idealized noise and operation models remain representative of near-term hardware constraints.

What would settle it

Measuring the actual average number of attempts required to generate the necessary Bell pairs for a given code distance in each architectural type on a real distributed quantum system.

Figures

Figures reproduced from arXiv: 2511.13657 by Eneet Kaur, Kaushik P. Seshadreesan, Nitish Kumar Chandra.

Figure 1
Figure 1. Figure 1: Teleported non-local CNOT using a shared Bell pair. [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Basic Protocol: Entanglement purification and intercell GHZ preparation with parity projection. (a) Two heralded Bell pairs (grey stars) are distilled using bilateral CNOTs and Z-basis measurements; when both outcomes are +1 as per Extreme Photon Loss (EPL) protocol [27], the remaining pair (blue star) has higher fidelity. (b) Purified intercell Bell pairs are combined by local entangling gates to form a d… view at source ↗
Figure 3
Figure 3. Figure 3: Expected entanglement link generation attempts per [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Expected entanglement link generation attempts per [PITH_FULL_IMAGE:figures/full_fig_p006_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Schematic showing monolithic and distributed implementations of stabilizer measurements in the toric code with [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Left: Multiple surface code blocks are hosted on separate hardware modules, each connected via a reconfigurable [PITH_FULL_IMAGE:figures/full_fig_p008_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Expected Bell pair attempts per stabilizer type per [PITH_FULL_IMAGE:figures/full_fig_p008_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: Depiction of a distributed quantum computing (DQC) system in which individual quantum processors are connected [PITH_FULL_IMAGE:figures/full_fig_p009_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: Average number of Bell pair generation attempts [PITH_FULL_IMAGE:figures/full_fig_p009_9.png] view at source ↗
read the original abstract

Fault tolerant quantum computation over distributed quantum computing (DQC) platforms requires careful evaluation of resource requirements and noise thresholds. As quantum hardware advances toward modular and networked architectures, various fault tolerant DQC schemes have been proposed, which can be broadly categorized into three architectural types. Type 1 architectures consist of small quantum nodes connected via Greenberger-Horne-Zeilinger (GHZ) states, enabling nonlocal stabilizer measurements. Type 2 architectures distribute a large error correcting code block across multiple modules, with most stabilizer measurements remaining local, except for a small subset at patch boundaries that are performed using nonlocal CNOT gates. Type 3 architectures assign code blocks to distinct modules and can perform fault tolerant operations such as transversal gates, lattice surgery, and teleportation to implement logical operations between code blocks. Using the planar surface code and toric code as representative examples, we analyze how the resource requirements, particularly the number of Bell pairs and the average number of generation attempts, scale with increasing code distance across different architectural designs. This analysis provides valuable insights for identifying architectures well suited to fault tolerant distributed quantum computation under near term hardware and resource constraints.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

0 major / 3 minor

Summary. The manuscript categorizes fault-tolerant distributed quantum computing (DQC) architectures into three types—small nodes using GHZ states for nonlocal stabilizers, distributed code blocks with mostly local stabilizers and boundary nonlocal CNOTs, and separate code blocks using transversal gates/lattice surgery/teleportation—and derives the scaling of Bell-pair counts and average generation attempts with code distance d for the planar surface code and toric code via explicit counting arguments based on stabilizer measurements and patch-boundary constructions.

Significance. If the scalings hold under the stated assumptions, the work supplies concrete, reproducible resource estimates that can guide architecture selection for near-term modular hardware. The explicit counting arguments grounded in standard surface-code error models (local Pauli noise, perfect intra-module gates) and the absence of fitted parameters are particular strengths, enabling direct comparison of entanglement overheads across designs.

minor comments (3)
  1. [Abstract] Abstract: the reference to 'near term hardware and resource constraints' would be strengthened by a brief statement of the concrete noise model (e.g., depolarizing rate or gate fidelity) assumed in the counting arguments.
  2. [Section 5] Section 5 (Conclusions): a compact summary table listing the leading-order Bell-pair scaling for each architecture and code family would improve readability and allow immediate cross-comparison of the reported overheads.
  3. [Notation] Notation throughout: ensure the symbol for code distance is used uniformly (d) and that the distinction between physical and logical patch sizes is stated explicitly when counting boundary operations.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their detailed summary of the manuscript and the positive significance assessment. We agree that the explicit counting arguments provide concrete resource estimates for guiding architecture selection. The recommendation for minor revision is noted. As the report does not list any specific major comments, we do not have point-by-point responses to major comments. We will prepare the revised manuscript accordingly.

Circularity Check

0 steps flagged

No significant circularity; derivations rest on standard stabilizer counting

full rationale

The paper categorizes DQC architectures into three types and derives scaling of Bell-pair counts and generation attempts versus code distance for planar surface and toric codes. These counts follow directly from explicit, standard constructions of nonlocal stabilizer measurements, patch-boundary CNOTs, and transversal/lattice-surgery operations under the usual local Pauli noise model. No fitted parameters are redefined as predictions, no self-citation chain supplies a uniqueness theorem or ansatz that the present work then treats as external, and the counting arguments remain independent of the target overhead formulas. The analysis is therefore self-contained against external quantum-error-correction benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review supplies no explicit free parameters, axioms, or invented entities; all such elements would need to be extracted from the full manuscript.

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