pith. sign in

arxiv: 2604.16236 · v2 · pith:CQ7GMGEJnew · submitted 2026-04-17 · 🪐 quant-ph

Long-term Performance Analysis of a Commercial QKD Device Under Real-world Deployment Conditions

Alisson Tezzin , Gustavo M. Uhdre , Oscar Martins , Sabrina Rufo , Vitor G.A. Carneiro This is my paper

Pith reviewed 2026-05-21 00:30 UTC · model grok-4.3

classification 🪐 quant-ph
keywords Quantum Key DistributionCommercial QKDReal-world deploymentTropical climateQBERVisibilityPerformance analysisField conditions
0
0 comments X

The pith

A commercial QKD system maintains visibility above 97% and QBER below 1% during extended real-world operation in tropical conditions.

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

The paper presents a long-term performance study of ID Quantique's Clavis XGR quantum key distribution device deployed in the Hermes Quantum Network in Brazil. It tracks key metrics such as secret key rate, quantum bit error rate, visibility, and detection counts over time on a 40.3 km indoor fiber link and a 3.5 km outdoor underground fiber link. The analysis covers both unregulated tropical ambient conditions and controlled thermal variations. A sympathetic reader cares about this because it offers concrete data on how commercial QKD systems behave in practical field settings, helping to set expectations for their use in building quantum-safe communication infrastructures.

Core claim

The ID Quantique Clavis XGR system exhibits excellent overall baseline resilience under real-world deployment conditions, with the system maintaining visibility above 97% and QBER below 1% on average across the two optical links despite tropical ambient fluctuations and thermal stress.

What carries the argument

Continuous long-term monitoring of operational metrics including secret key rate, QBER, visibility, and detection counts on indoor spooled and outdoor deployed fiber links.

If this is right

  • The system demonstrates sufficient stability for operational use in similar environments.
  • Thermal management emerges as a key factor for sustaining performance in tropical climates.
  • Realistic expectations can be formed for the reliability of commercial QKD in field deployments.
  • Insights into behavior under both indoor and outdoor fiber configurations inform network design choices.

Where Pith is reading between the lines

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

  • This performance level implies that additional environmental controls may not be strictly necessary for basic operation in tropical areas.
  • Extending the study to other commercial QKD vendors could reveal whether this resilience is typical or device-specific.
  • Integration with existing network infrastructure in Brazil suggests scalability for broader quantum communication networks.

Load-bearing premise

The monitored links and sensors accurately capture typical operational conditions without unaccounted installation-specific effects or measurement offsets that would alter the reported averages.

What would settle it

A long-term observation in the same or equivalent setup showing average visibility dropping below 97% or QBER rising above 1% under similar tropical conditions would challenge the resilience claim.

Figures

Figures reproduced from arXiv: 2604.16236 by Alisson Tezzin, Gustavo M. Uhdre, Oscar Martins, Sabrina Rufo, Vitor G.A. Carneiro.

Figure 1
Figure 1. Figure 1: FIG. 1. Timeline of the experimental campaign. The upper timeline (blue) represents the Indoor channel activities, whereas the [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Internal temperatures of Alice and Bob Units during [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Key rate estimation during the indoor long-term per [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. Key rate compared to visibility throughout the indoor [PITH_FULL_IMAGE:figures/full_fig_p006_6.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Detection count and Alice’s temperature during the [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
Figure 10
Figure 10. Figure 10: FIG. 10. Key Rate and visibility observed during the outdoor [PITH_FULL_IMAGE:figures/full_fig_p007_10.png] view at source ↗
Figure 9
Figure 9. Figure 9: FIG. 9. QBER and external temperature dynamics during [PITH_FULL_IMAGE:figures/full_fig_p007_9.png] view at source ↗
Figure 11
Figure 11. Figure 11: FIG. 11. Internal and external temperatures during the con [PITH_FULL_IMAGE:figures/full_fig_p008_11.png] view at source ↗
Figure 12
Figure 12. Figure 12: FIG. 12. Key Rate evolution compared to the external lab [PITH_FULL_IMAGE:figures/full_fig_p008_12.png] view at source ↗
Figure 13
Figure 13. Figure 13: FIG. 13. QBER and external temperature dynamics. Data [PITH_FULL_IMAGE:figures/full_fig_p009_13.png] view at source ↗
Figure 14
Figure 14. Figure 14: FIG. 14. Detection count and external temperature evolution [PITH_FULL_IMAGE:figures/full_fig_p009_14.png] view at source ↗
Figure 16
Figure 16. Figure 16: FIG. 16. Internal and external temperatures during the con [PITH_FULL_IMAGE:figures/full_fig_p009_16.png] view at source ↗
Figure 19
Figure 19. Figure 19: FIG. 19. QBER and external temperature dynamics (10- [PITH_FULL_IMAGE:figures/full_fig_p010_19.png] view at source ↗
Figure 20
Figure 20. Figure 20: FIG. 20. Correlation between Visibility and Key Rate during [PITH_FULL_IMAGE:figures/full_fig_p010_20.png] view at source ↗
Figure 18
Figure 18. Figure 18: FIG. 18. Key Rate evolution compared to the external labo [PITH_FULL_IMAGE:figures/full_fig_p010_18.png] view at source ↗
read the original abstract

Quantum key distribution (QKD) has reached a commercially viable stage, with several companies offering hardware systems designed for operational deployment. Evaluating the performance of commercial QKD devices under real-world deployment conditions is essential for users seeking to understand the practical limitations and operational reliability of these systems. In this paper, we present a long-term performance analysis of ID Quantique's Clavis XGR deployed within the Hermes Quantum Network, in Brazil. Our study provides a detailed characterization of key operational metrics, such as secret key rate, quantum bit error rate (QBER), visibility, and detection counts, mapping their behavior over extended periods of continuous operation. We analyze the system's stability across two distinct optical links: a 40.3 km indoor spooled fiber and a 3.5 km outdoor deployed underground fiber. Monitored under both unregulated tropical ambient fluctuations and actively controlled thermal stress, our results demonstrate excellent overall baseline resilience, with the system maintaining visibility above 97% and QBER below 1% on average. These findings provide practical insights into the expected behavior and thermal bottlenecks of commercial QKD systems in field deployments, particularly in tropical climates, helping to inform realistic expectations for operational quantum-safe infrastructures.

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 / 2 minor

Summary. The manuscript reports a long-term empirical study of ID Quantique's Clavis XGR commercial QKD system deployed in the Hermes Quantum Network in Brazil. It characterizes operational metrics (secret key rate, QBER, visibility, detection counts) over extended continuous operation on two links—a 40.3 km indoor spooled fiber and a 3.5 km outdoor underground fiber—under unregulated tropical ambient conditions and controlled thermal stress. The central claim is that the system shows excellent baseline resilience, maintaining visibility above 97% and QBER below 1% on average.

Significance. If the reported averages are statistically robust, the work supplies practical field data on commercial QKD performance in tropical climates, highlighting thermal and environmental stability limits that can inform realistic expectations and deployment planning for quantum-safe networks.

major comments (2)
  1. Abstract and results sections: the headline averages (visibility >97%, QBER <1%) are presented without error bars, standard deviations, confidence intervals, or any description of the underlying statistical procedure, time-window selection, or data-exclusion criteria. Because the resilience claim rests directly on these aggregate figures and the two links experience markedly different environmental exposures, the absence of variability measures prevents assessment of whether the reported performance is representative or dominated by particular stable intervals.
  2. Experimental setup / link description: for the 3.5 km outdoor underground fiber, the monitoring of ambient fluctuations and thermal stress is described, yet no quantitative discussion is given of possible unaccounted installation-specific effects (humidity-driven polarization drift, soil-induced micro-bending, or calibration offsets in the Clavis XGR detection counts). Such factors could systematically shift the measured QBER and visibility, directly affecting the validity of the aggregate resilience statement.
minor comments (2)
  1. The manuscript would benefit from explicit time-series plots (with shaded variability bands) or tabulated per-link statistics to allow readers to verify the claimed averages.
  2. Notation for detection counts and secret-key-rate extraction should be cross-referenced to the Clavis XGR manual or standard QKD formulas to improve reproducibility.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive comments, which help improve the clarity and robustness of our empirical study on the Clavis XGR system. We address each major comment below and have prepared revisions accordingly.

read point-by-point responses

  1. Referee: Abstract and results sections: the headline averages (visibility >97%, QBER <1%) are presented without error bars, standard deviations, confidence intervals, or any description of the underlying statistical procedure, time-window selection, or data-exclusion criteria. Because the resilience claim rests directly on these aggregate figures and the two links experience markedly different environmental exposures, the absence of variability measures prevents assessment of whether the reported performance is representative or dominated by particular stable intervals.

    Authors: We agree that the reported averages would be more informative with accompanying measures of variability and an explicit description of the analysis methodology. In the revised manuscript we will add standard deviations and error bars to the visibility and QBER averages in both the abstract and results sections. We will also insert a short paragraph in the results section that specifies the time-window selection (continuous 24-hour blocks), the total data volume analyzed, and the criteria used for any data exclusion (primarily brief calibration intervals). These additions will allow readers to evaluate the representativeness of the figures across the two links with different environmental exposures. revision: yes

  2. Referee: Experimental setup / link description: for the 3.5 km outdoor underground fiber, the monitoring of ambient fluctuations and thermal stress is described, yet no quantitative discussion is given of possible unaccounted installation-specific effects (humidity-driven polarization drift, soil-induced micro-bending, or calibration offsets in the Clavis XGR detection counts). Such factors could systematically shift the measured QBER and visibility, directly affecting the validity of the aggregate resilience statement.

    Authors: We acknowledge that the manuscript does not provide a quantitative treatment of installation-specific effects such as humidity-driven polarization drift or soil-induced micro-bending for the outdoor link. Our long-term dataset shows consistently high visibility and low QBER under the monitored tropical conditions, which indicates that any such effects remained within the system's operational tolerance. In the revised version we will expand the experimental-setup section with a qualitative discussion of these potential factors and explain why the observed stability over months of continuous operation suggests they did not dominate the measured performance. A full quantitative model would require additional dedicated measurements that lie outside the scope of the present empirical study. revision: partial

Circularity Check

0 steps flagged

No circularity: direct empirical reporting of monitored QKD metrics

full rationale

The paper consists entirely of long-term observational measurements of standard commercial QKD performance indicators (visibility, QBER, secret key rate, detection counts) on two specific fiber links under tropical conditions. No derivations, fitted models, predictions, ansatzes, or uniqueness theorems are invoked. The headline averages (visibility >97%, QBER <1%) are computed directly from the collected sensor data without any reduction to constructed inputs or self-referential steps. The analysis is self-contained as a field-deployment report.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Experimental performance study using standard QKD observables; no free parameters, mathematical axioms, or new postulated entities are introduced.

pith-pipeline@v0.9.0 · 5758 in / 1025 out tokens · 39905 ms · 2026-05-21T00:30:07.955531+00:00 · methodology

Review history (2 revisions) →

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

What do these tags mean?
matches
The paper's claim is directly supported by a theorem in the formal canon.
supports
The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
extends
The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses
The paper appears to rely on the theorem as machinery.
contradicts
The paper's claim conflicts with a theorem or certificate in the canon.
unclear
Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.

Reference graph

Works this paper leans on

23 extracted references · 23 canonical work pages

  1. [1]

    Indoor Channel (23 Oct - 17 Nov) Despite the unregulated laboratory conditions, the Al- ice and Bob units maintained relatively stable tempera- tures, remaining mostly within a 3-degree variation band (Fig. 2). Specifically, the average temperatures for Al- ice and Bob were33±1 ◦Cand30±1 ◦C, respectively, as shown in Table II. The highest temperatures rec...

    work page

  2. [2]

    Outdoor Channel (19 Nov - 17 Dec) The temperature profiles for Alice and Bob are shown in Fig. 7. Whereas the unit temperatures remained rel- atively stable throughout the spooled indoor fiber tests, they exhibited considerable oscillations during this stage of the experiment. As shown in Table II, average tem- peratures for both units were roughly 1°C hi...

    work page 2025

  3. [3]

    Indoor Channel (24 - 30 Dec) In contrast to the unregulated fluctuations of the pre- vious phase, the temperature profile in this stage ex- hibits clear, stepwise transitions corresponding to the three imposed regimes. Fig. 11 demonstrates that, for the spooled indoor fiber, the internal temperatures of the units tightly track the external thermal trends....

    work page

  4. [4]

    Furthermore, the transition between Stages 2 and 3 —marked by a significant temperature shift — was accompanied by a substantial relative oscillation in the detection frequency

    We observe that third stage, characterized by higher thermal instability compared to the previous ones, ex- hibited a higher variance in the detection count, as ex- pected. Furthermore, the transition between Stages 2 and 3 —marked by a significant temperature shift — was accompanied by a substantial relative oscillation in the detection frequency. 9 FIG....

    work page

  5. [5]

    Outdoor Channel (03 - 09 Jan ) Figure 16 presents the raw temperature profiles for the installed fiber campaign. Due to external weather condi- tions influencing the laboratory environment, the mean temperature of Stage 1 was higher than that of Stage 2, deviating from the intended stepwise increase. Ad- ditionally, contrary to the trend observed in the i...

    work page 2023

  6. [6]

    Pirandola, U

    S. Pirandola, U. L. Andersen, L. Banchi, M. Berta, D. Bunandar, R. Colbeck, D. Englund, T. Gehring, C. Lupo, C. Ottaviani, J. L. Pereira, M. Razavi, J. S. 12 Shaari, M. Tomamichel, V. C. Usenko, G. Vallone, P. Vil- loresi, and P. Wallden, Adv. Opt. Photon.12, 1012 (2020)

    work page 2020

  7. [7]

    Stanley, Y

    M. Stanley, Y. Gui, D. Unnikrishnan, S. Hall, and I. Fatadin, Journal of Physics: Conference Series2416, 012001 (2022)

    work page 2022

  8. [8]

    Zhang, H

    H. Zhang, H. Zhu, R. He, Y. Zhang, C. Ding, L. Hanzo, and W. Gao, Nature Reviews Electrical Engineering2, 806 (2025)

    work page 2025

  9. [9]

    Bozzio, C

    M. Bozzio, C. Crépeau, P. Wallden, and P. Walther, Rev. Mod. Phys.97, 045006 (2025)

    work page 2025

  10. [10]

    M. U. Rehman, Quantum-safe cryptography: Compa- nies across the landscape – 2026, The Quantum Insider (2026), accessed on: 16 Apr. 2026

    work page 2026

  11. [11]

    C. H. Bennett and G. Brassard, Theoretical computer science560, 7 (2014)

    work page 2014

  12. [12]

    G. P. Agrawal,Fiber-Optic Communication Systems (John Wiley & Sons, Ltd, 2010)

    work page 2010

  13. [13]

    H. Ma, D. Liu, C. Feng, and L. Feng, inAOPC 2021: Micro-optics and MOEMS, Vol. 12066, edited by Y. Wang, H. Xie, and Y.-F. Xiao, International Society for Optics and Photonics (SPIE, 2021) p. 1206614

    work page 2021

  14. [14]

    S. M. Sze and K. K. Ng,Physics of Semiconductor De- vices(John Wiley & Sons, Ltd, 2006)

    work page 2006

  15. [15]

    Hofbauer, B

    M. Hofbauer, B. Steindl, and H. Zimmer- mann, Journal of Sensors2018, 9585931 (2018), https://onlinelibrary.wiley.com/doi/pdf/10.1155/2018/9585931

    work page doi:10.1155/2018/9585931 2018

  16. [16]

    R. H. Hadfield, Nature Photonics3, 696 (2009)

    work page 2009

  17. [17]

    G. P. Temporão, F. R. V. B. d. Melo, and A. Z. Khoury, inAnais do I Workshop de Redes Quânticas (WQuNets)(Sociedade Brasileira de Computação, Porto Alegre, 2024) pp. 19–24

    work page 2024

  18. [18]

    H.-K. Lo, H. F. Chau, and M. Ardehali, J. Cryptol.18, 133–165 (2005)

    work page 2005

  19. [19]

    Brendel, N

    J. Brendel, N. Gisin, W. Tittel, and H. Zbinden, Physical review letters82, 2594 (1999)

    work page 1999

  20. [20]

    Tittel, J

    W. Tittel, J. Brendel, H. Zbinden, and N. Gisin, Phys. Rev. Lett.84, 4737 (2000)

    work page 2000

  21. [21]

    H.-K. Lo, X. Ma, and K. Chen, Physical review letters 94, 230504 (2005)

    work page 2005

  22. [22]

    Hwang, Physical review letters91, 057901 (2003)

    W.-Y. Hwang, Physical review letters91, 057901 (2003). [18]Clavis XGR QKD System Brochure, ID Quantique (2025), copyright 2026 ID Quantique SA - All rights re- served - G.192.0121-PB-2.4 - Specifications as of Febru- ary 2026. Accessed: April 15, 2026

    work page 2003

  23. [23]

    Kawakami, A

    S. Kawakami, A. Taniguchi, Y. Tonomura, K. Takasugi, and K. Azuma, Phys. Rev. Appl.24, 054070 (2025)

    work page 2025