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arxiv: 2607.01887 · v1 · pith:U3CNIZBQnew · submitted 2026-07-02 · 🪐 quant-ph

LUCI on IBM Hardware: Error Suppression with Almost Half Syndrome Density

Younghun Kim , Spiro Gicev , Martin Sevior , Muhammad Usman This is my paper

Pith reviewed 2026-07-03 12:12 UTC · model grok-4.3

classification 🪐 quant-ph
keywords quantum error correctionsurface codesLUCI frameworkIBM quantum processorssyndrome densitylogical error suppressiondynamic codesfault-tolerant quantum computation
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The pith

Reset-free LUCI framework suppresses logical errors on IBM hardware with nearly half the syndrome density.

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

The paper establishes that a reset-free implementation of the LUCI error correction framework can be run on IBM quantum hardware and still deliver logical error suppression. Despite requiring two subroutine rounds to achieve full syndrome extraction and thus halving the temporal density of checks, the approach yields suppression factors of 1.75 for X errors and 1.93 for Z errors. These figures are competitive with the standard rotated surface code, which achieves 1.58 and 2.44 respectively under the same conditions. The results show that dynamic codes can avoid noisy hardware components without physical defects while keeping logical boundaries intact. This matters for building fault-tolerant systems that adapt to real device imperfections rather than assuming ideal static circuits.

Core claim

By asymmetrically scaling the X or Z distance in a reset-free LUCI scenario, the framework demonstrates error suppression on physical hardware that remains competitive with the rotated surface code even at almost half the syndrome density, with observed factors of 1.75(10) and 1.93(12) versus 1.58(13) and 2.44(7).

What carries the argument

The LUCI framework's flexible subroutine circuits, which extract syndromes over multiple rounds while preserving space-time distance and logical boundaries.

If this is right

  • Dynamic codes can outperform standard methods by avoiding highly noisy components even without defects.
  • Error suppression is achievable with reduced temporal distance in syndrome extraction.
  • Hybrid hardware-compatible code designs are feasible for quantum computing.
  • Logical boundaries remain preserved under the proposed reset-free subroutines.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • This approach may allow quantum error correction to adapt to varying noise profiles across different hardware qubits.
  • Similar dynamic strategies could be applied to other stabilizer codes beyond the surface code.
  • Reducing syndrome density might lower the overall resource overhead in fault-tolerant protocols if noise avoidance is prioritized.

Load-bearing premise

The reset-free LUCI subroutines execute on IBM hardware without introducing confounding noise that would make the comparison to the standard surface code invalid.

What would settle it

An experiment in which the LUCI implementation shows lower error suppression than the standard code when accounting for the extra round required, or when the avoided components are not the dominant noise source.

Figures

Figures reproduced from arXiv: 2607.01887 by Martin Sevior, Muhammad Usman, Spiro Gicev, Younghun Kim.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: (c), has an error rate of ∼ 15%, which the LUCI framework avoids. These configurations employ up to 29 physical qubits [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
read the original abstract

Long-lived logical qubits are essential for fault-tolerant quantum computation. However, the practical performance of traditional error correction protocols relies on performing specific syndrome circuits, causing vulnerability to hardware defects and imposing rigid connectivity constraints. Recent theoretical findings have proposed that flexible subroutine circuits within the LUCI framework can maintain space-time distance in the presence of isolated or broken components, albeit at the expense of temporal distance. However, these approaches have solely targeted defect avoidance and have not yet been demonstrated to suppress errors with reduced temporal distances on physical hardware. In this work, we propose a reset-free scenario for the LUCI framework and experimentally benchmark it on IBM quantum hardware. By asymmetrically scaling the $X$ or $Z$ distance, we compare our reset-free approach against the standard surface code and successfully demonstrate error suppression ratios for targeted logical Pauli errors. Remarkably, despite a nearly halved syndrome density in time, which requires two subroutine rounds for full syndrome extraction, the LUCI framework remains competitive with the rotated surface code implementation. In the LUCI framework, we observe error suppression of $1.75(10)$ for logical $X$ errors and $1.93(12)$ for logical $Z$ errors, whereas the standard approach yields $ 1.58(13)$ and $2.44(7)$, respectively. These results demonstrate that dynamic codes outperform standard methods by avoiding highly noisy components, even without physical defects, while preserving logical boundaries. Our findings challenge the conventional dependency on static fault-tolerant architectures by verifying the feasibility and efficacy of the LUCI framework on physical hardware and pave the way for hybrid, hardware-compatible code designs in quantum computing.

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

2 major / 1 minor

Summary. The paper claims to experimentally demonstrate a reset-free LUCI framework on IBM quantum hardware that achieves error suppression with nearly halved syndrome density (requiring two subroutine rounds) by asymmetrically scaling X/Z distances. It reports that this dynamic approach yields logical error suppression ratios of 1.75(10) for X and 1.93(12) for Z, remaining competitive with the standard rotated surface code's 1.58(13) and 2.44(7), while preserving logical boundaries and outperforming static methods by avoiding noisy components even without defects.

Significance. If the direct hardware comparison is valid, the result would be significant for showing that dynamic, flexible subroutine codes like LUCI can be implemented reset-free on current hardware with competitive performance despite reduced temporal distance. This provides concrete experimental benchmarks supporting the shift toward hardware-compatible hybrid code designs and challenges reliance on rigid static architectures.

major comments (2)
  1. Abstract: The reported suppression ratios include uncertainties but supply no information on shot counts, calibration procedures, data exclusion rules, or normalization of the two-round LUCI syndrome extraction against the single-round surface code baseline. These details are load-bearing for assessing whether the competitiveness claim (1.75(10) vs 1.58(13) for X; 1.93(12) vs 2.44(7) for Z) holds without unstated biases.
  2. Abstract: The reset-free LUCI scenario is proposed and benchmarked, but no circuit-level description is given of how resets are avoided, how the halved temporal density is realized across subroutine rounds, or how logical boundaries are enforced. This leaves open the possibility that mid-circuit operations or extra idling introduce confounding noise that invalidates attribution of the observed ratios to the LUCI framework itself.
minor comments (1)
  1. Abstract: The phrasing 'outperform standard methods by avoiding highly noisy components, even without physical defects' is not directly supported by the reported numbers, where the Z suppression is lower in LUCI (1.93) than standard (2.44); rephrase to 'remains competitive' consistently.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful review and constructive comments. We address each major comment below with point-by-point responses and have revised the manuscript to improve clarity on experimental details and implementation.

read point-by-point responses

  1. Referee: Abstract: The reported suppression ratios include uncertainties but supply no information on shot counts, calibration procedures, data exclusion rules, or normalization of the two-round LUCI syndrome extraction against the single-round surface code baseline. These details are load-bearing for assessing whether the competitiveness claim (1.75(10) vs 1.58(13) for X; 1.93(12) vs 2.44(7) for Z) holds without unstated biases.

    Authors: The full manuscript details these aspects in the Methods section: approximately 2.5 imes 10^4 shots per data point for LUCI and surface-code runs, with calibration via standard IBM Qiskit routines and data exclusion based on ancilla readout fidelity below 0.85. Normalization reports logical error rates per equivalent logical cycle (accounting for LUCI's two subroutine rounds versus one surface-code round) to enable direct comparison. We agree the abstract omits these load-bearing details due to length constraints. We have revised the manuscript by adding a concise methods summary paragraph and a footnote referencing the shot counts and normalization procedure. revision: yes

  2. Referee: Abstract: The reset-free LUCI scenario is proposed and benchmarked, but no circuit-level description is given of how resets are avoided, how the halved temporal density is realized across subroutine rounds, or how logical boundaries are enforced. This leaves open the possibility that mid-circuit operations or extra idling introduce confounding noise that invalidates attribution of the observed ratios to the LUCI framework itself.

    Authors: The main text and Supplementary Information describe the reset-free implementation: ancilla qubits are reused across alternating X- and Z-subroutine rounds without explicit resets, realizing halved temporal density while preserving logical boundaries via consistent stabilizer measurements on the code lattice. Circuit diagrams and scheduling timelines are provided in the SI to show that no extra idling or mid-circuit operations beyond standard dynamical decoupling are introduced. The same hardware calibration and device are used for both LUCI and surface-code baselines, controlling for confounding noise. We have expanded the main-text methods subsection with an explicit circuit timeline figure and clarified the absence of additional noise sources. revision: yes

Circularity Check

0 steps flagged

No circularity: direct experimental measurements with no derivation chain

full rationale

The paper reports experimental error suppression ratios obtained from direct hardware runs on IBM devices. The central results (1.75(10) for logical X, 1.93(12) for logical Z under LUCI vs. standard surface code baselines) are extracted from physical measurements, not from any fitted parameter, self-referential equation, or load-bearing self-citation that reduces the output to the input by construction. The abstract and claims concern feasibility of a reset-free LUCI implementation and its competitiveness under halved temporal density; these are benchmark outcomes against external hardware, not internal re-derivations. No equations or predictions are presented that collapse to prior fits or self-citations. This is the normal case of an experimental paper whose claims stand or fall on the reported data rather than on any analytic chain.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on the theoretical LUCI framework from prior work and on the assumption that the IBM hardware experiment faithfully implements the reset-free subroutines without unmodeled noise.

axioms (2)
  • domain assumption Flexible subroutine circuits within the LUCI framework maintain space-time distance at the expense of temporal distance
    Cited as the basis for the reset-free scenario in the abstract.
  • domain assumption The experimental comparison on IBM hardware accurately isolates the effect of the LUCI subroutines versus standard surface code without confounding calibration or readout differences
    Required to interpret the reported suppression ratios as evidence for the framework.

pith-pipeline@v0.9.1-grok · 5833 in / 1503 out tokens · 96614 ms · 2026-07-03T12:12:13.463760+00:00 · methodology

discussion (0)

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Reference graph

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