{"id":"0d997f5d-e498-4adf-8a38-a81ca400bc6e","arxiv_id":"2411.15058","paper_version":3,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":0,"one_line_summary":"Dielectric HDPE waveguides provide low-loss, low-heat-load transmission of 75-110 GHz signals in a dilution refrigerator, enabling superconducting cavity measurements with Q above 15 million.","lead":"The authors built and tested a cryogenic data link for millimeter-wave signals using flexible plastic (HDPE) waveguides, working down to 10 mK. They show the lines carry low-loss signals with negligible heat load, and used them to measure a superconducting cavity with quality factors above 15 million.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The no-TLS and single-photon Q=15M claims rest on attributing the low-power Qi drop in Fig. 10 to drift, with no quantitative drift test provided.","rationale":"The reader's weakest assumption is exactly the drift explanation for the low-power Qi decrease, and my analysis agrees: this is the most load-bearing concern for the paper's headline claim about TLS and the single-photon Q value. The central contribution of the paper, a working dielectric-waveguide mm-wave link at millikelvin temperatures, is well supported by transmission measurements, thermal-load estimates, crosstalk suppression, and the observation of high-Q superconducting Fabry-Perot resonances. Those results do not depend on the drift assumption. The no-TLS conclusion, however, is not independently supported: the observed decrease of Qi at low photon numbers is, if anything, a TLS-like signature, and the manuscript's dismissal of it as drift is plausible but unverified. This does not require rejecting the paper; it requires conditioning the no-TLS and single-photon Q claims on a dedicated drift-control measurement. Hence the verdict should remain CONDITIONAL, which is what the reader already recommended. The proposed interleaved power-dependence test would settle the question directly by distinguishing a history-dependent drift effect from a reproducible intrinsic loss mechanism.","tokens_in":9697,"tokens_out":3273,"duration_ms":36589,"concrete_test":"Re-measure the power dependence of mode A at 10 mK using interleaved high-power and low-power points with shortened averaging time per point, and return to a fixed high-power reference (e.g., 1e5 photons) after every low-power measurement. If Qi reproducibly recovers to ~15M at the reference point after every low-power excursion, drift is confirmed and the no-TLS conclusion is supported; if low-power Qi reproducibly returns to ~11M independent of measurement history, the decrease is an intrinsic power-dependent loss and the no-TLS/single-photon claim must be revised. As a secondary check, fit the low-power tail with a TLS saturation model: 1/Qi = 1/Q0 + A/sqrt(1 + n/n_c), and compare the fitted n_c with the independently estimated average photon number.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The strongest claim includes 'quality factors up to 15 million in the single photon limit' and 'no evident influence of atomic two-level systems.' Both depend on interpreting the low-photon-number decrease of Qi in Fig. 10 (top) as parameter drift, not as an intrinsic loss mechanism. The data show Qi falling from ~15M at high photon numbers to ~11M below about 100 photons; this is the direction expected for TLS loss, where low power leads to stronger TLS absorption. The text attributes the decrease to multi-hour averaging and drift, but provides no quantitative drift model, no repeated high-power/low-power cycles, and no error analysis that separates drift from a reproducible power dependence. The stated frequency stability of ±1.7 kHz does not bound the circle-fit Qi uncertainty, because Qi extraction is sensitive to slowly varying cable phase, coupling, and background that need not shift the resonance center frequency. If the low-power decrease is real, the no-TLS conclusion is wrong, and '15 million in the single photon limit' is unsupported: the lowest measured mean photon number is about 3, and at that point Qi has already dropped to ~11M. The dielectric-waveguide feasibility demonstration survives, but the headline physics claim about TLS is conditional on the drift assumption.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper describes a cryogenic millimeter-wave setup based on dielectric waveguides (DWGs) made of high-density polyethylene (HDPE), designed to operate from room temperature to 10 mK in the 75-110 GHz band. The authors report room-temperature and cryogenic transmission measurements of transparent and black HDPE DWGs, thermal-load estimates, and an attenuation scheme using black HDPE or copper-loaded coatings. The setup is validated with a superconducting niobium-coated Fabry-Pérot cavity, for which they report internal quality factors up to about 15 million and coupling quality factors above 45 million, and they argue that atomic two-level systems have no evident influence.","tokens_in":9931,"tokens_out":5142,"duration_ms":48780,"significance":"If the reported results hold, the work provides a practical, low-heat-load alternative to metal waveguides for mm-wave quantum experiments, with the added capability of cold attenuation and infrared blocking. The paper includes direct S-parameter data, a thermal model, and a full system-level demonstration; these are concrete strengths. However, the headline physics claim about the absence of TLS losses is currently conditional on a drift interpretation that is not quantitatively supported, and the 'single photon limit' wording exceeds the displayed data.","major_comments":[{"comment":"The conclusion that two-level systems do not affect the cavity quality factor rests on attributing the drop in Qi from ~15 million to ~11 million at photon numbers below 100 (Fig. 10, top) to parameter drift during multi-hour averaging. The text offers no quantitative drift model, no repeated high-power/low-power cycles, and no independent bound on the circle-fit uncertainty from slowly varying cable phase, coupling, or background. Since a TLS-like loss mechanism would produce exactly this drop, the data as presented do not exclude a real power-dependent loss; please add a quantitative drift analysis or temper the no-TLS and single-photon-limit claims.","section":"III.B, Fig. 10 (top)"},{"comment":"The Abstract and Conclusion claim 'quality factors up to 15 million in the single photon limit,' but the lowest average photon number shown in Fig. 10 is about 3, and at that point the internal quality factor has already decreased to ~11 million. The maximum Qi of ~15 million is measured at photon numbers above 100, not in the single-photon regime; the current phrasing overstates what the data support. Please state the actual photon-number range and either replace 'single photon limit' with 'down to a few photons' or provide data at n < 1.","section":"Abstract and Conclusion; Section III.B, Fig. 10"},{"comment":"The reported cryogenic attenuation (0.6 dB/m for the transparent DWG at 2.5 K) is obtained by de-embedding from several cooldown cycles, and the text itself notes that the calibration is sensitive to non-stationary DWG-to-adapter impedance matching. No quantified error bars, repeated measurements, or alternative calibrations are provided, so the frequency-independent low-loss value is not fully established. Adding uncertainty estimates or reproducibility data would strengthen the central feasibility claim.","section":"II.D, Fig. 4"}],"minor_comments":[{"comment":"The sentence after the de-embedding discussion says 'Figure 2 shows the resulting transmission data'; this should reference Fig. 4, which displays the transmission data.","section":"II.D"},{"comment":"The phrase 'stainless steal' should read 'stainless steel'.","section":"II.B"},{"comment":"The caption begins with 'T op:' which appears to be a typesetting error for 'Top:'.","section":"Figure 2 caption"},{"comment":"The notation 'Qc(A) = 46 ± 3.5 10^6' should be typeset as (46 ± 3.5) × 10^6 to avoid ambiguity.","section":"III.B"},{"comment":"The phrases 'Indicated errors factored by two' and 'Blue errors factored by 15' are ambiguous; please specify whether the displayed error bars are raw, doubled, or multiplied by the given factor.","section":"Figure 10 caption"},{"comment":"The reference list appears under 'Appendix A' after the main text, but the body cites [1]-[23] as standard references; please reformat this as a conventional reference section.","section":"References"}],"recommendation":"major_revision","confidential_remarks":"The DWG engineering contribution is solid and likely acceptable after revision; however, the TLS/no-dissipation claim is an overreach relative to the data in Fig. 10. I would suggest the authors either strengthen the drift analysis or present the cavity results as a demonstration of high-Q operation at low photon numbers without asserting the absence of TLS."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Helmut,\n\nThe headline: this is a solid engineering demonstration that HDPE dielectric waveguides work at 10 mK for W-band signals, and the cavity results are a nice proof of use. The paper deserves a serious referee, but the abstract overstates the single-photon and no-TLS conclusions.\n\nWhat is actually new: Ref. [4] stopped at 4.2 K and did not put a device at the end of the line. This group extends to 10 mK, characterizes transparent vs. carbon-loaded HDPE at cryogenic temperature, adds metal mesh shielding, and measures a superconducting Fabry-Perot cavity with Qi over 15 million at 107 GHz. The transmission data (0.6 dB/m at 2.5 K for transparent HDPE) are direct S-parameter measurements, and the thermal anchoring scheme with WR10 transitions is practical. The heat load estimates are clearly labeled as estimates. This is exactly the kind of enabling work the mm-wave quantum community needs.\n\nThe soft spots are all around the cavity physics claims. Figure 10 shows Qi falling from about 15M to 11M as the photon number drops below 100. The text attributes this to parameter drift during multi-hour averaging, but offers no drift model, no repeated up/down sweeps, and no error analysis that separates drift from a reproducible power dependence. The stated frequency stability of ±1.7 kHz does not bound the circle-fit Qi error, because Qi is sensitive to slowly varying amplitude, cable phase, and background that need not shift the center frequency. The direction of the drop is exactly what TLS would do. So the conclusion 'no evident influence of two-level systems' is conditional on an untested assumption. And 'single photon limit' is generous: the lowest point is about 3 photons, and at that point Qi has already dropped to ~11M. The abstract's phrase 'quality factors up to 15 million in the single photon limit' is not supported by the data as presented. The feasibility demonstration survives; the headline physics claim needs either a drift-control measurement or a softer wording.\n\nMinor points: the de-embedded transmission curves have unquantified systematic uncertainty from adapter impedance changes, and the 10 GHz ripple is not error-bared. The black HDPE's low-temperature attenuation increase above 95 GHz is noted as unexplained, which is honest. Citations look fine; Ref. [4] is properly credited and the extension is real.\n\nBottom line: send this to review. The engineering is sound and publishable. Ask the authors to either substantiate the drift assumption or downgrade the abstract claims. The paper is worth reading for anyone building cryogenic mm-wave measurement chains.\n\nBest,\n\n[Your name]","headline":"Solid engineering demonstration of mK dielectric waveguides for W-band, but the no-TLS and single-photon claims in the abstract outrun the data.","tokens_in":10518,"tokens_out":2738,"would_cite":true,"duration_ms":25650,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"A cryogenic setup built on flexible plastic waveguides carries millimeter-wave signals into a 10 mK dilution refrigerator, and a superconducting Fabry–Pérot cavity measured with it shows internal quality factors up to 15 million at the…","keywords":["dielectric waveguide","millimeter-wave","cryogenic","Fabry-Pérot cavity","superconducting resonator","quality factor","two-level systems","W-band"],"falsifier":"Measure the same cavity mode's internal quality factor versus photon number with a scheme that eliminates long-term drift, for instance by interleaving a high-power reference with each low-power point or by using faster phase-locked averaging. If the quality factor still falls below 100 photons after drift correction, the claim that two-level systems do not affect the cavity would be falsified.","tokens_in":9544,"feed_emoji":"📡","tokens_out":4285,"duration_ms":41347,"temperature":0.7,"pith_summary":"The paper proposes replacing rigid metallic hollow waveguides with flexible dielectric strips made of high-density polyethylene to carry millimeter-wave signals in the 75–110 GHz band from room temperature down to 10 mK. The authors show that these waveguides combine low, roughly frequency-independent photon loss with a very small heat load at each cryogenic stage, and that they can be thermally anchored, shielded against crosstalk, and attenuntated using black HDPE or copper-powder coatings. To demonstrate suitability for low-photon-number quantum measurements, they mounted a superconducting Fabry–Pérot cavity at the cold stage and measured resonances with internal quality factors up to about 15 million at photon numbers as low as a few. They interpret the flat quality factor versus power and temperature as evidence that atomic two-level systems in the cavity surfaces do not limit the resonator. If this is right, it opens a practical route to millimeter-wave quantum experiments that need low noise and low photon numbers.","feed_headline":"Superconducting cavity holds Q of 15 million at 10 mK","feed_subtitle":"Flexible plastic waveguides deliver 100 GHz signals to a dilution fridge, reaching single-photon sensitivity.","key_machinery":"The dielectric waveguide itself is the central object: a rectangular strip of HDPE (relative permittivity 2.33) surrounded by polyurethane foam, guiding mm-waves by total internal reflection with an evanescent field that can be used for coupling and attenuation. Thermal anchoring is achieved by metallic transitions at each temperature stage, where tapered waveguide ends couple into WR10 rectangular waveguides. The test device is a Fabry–Pérot cavity with sputtered niobium mirrors coupled through a small sub-cutoff hole to a WR10 waveguide, and resonance parameters are extracted with a circle-fit algorithm.","core_discovery":"The central claim is that dielectric waveguides made from strips of HDPE embedded in low-loss foam provide a viable, low-heat-leak signal path for W-band measurements at milli-Kelvin temperatures, and that the setup is sensitive enough to resolve the intrinsic quality factor of a superconducting Fabry–Pérot cavity down to the single-photon limit. Multiple cavity modes were observed at 10 mK, with internal quality factors up to 15 million and coupling quality factors above 45 million. The authors find no evident influence of atomic two-level systems: the internal quality factor does not rise substantially with photon number above roughly 1000 photons, as it would for TLS-limited resonators; the modest decrease below 100 photons is attributed to parameter drift during multi-hour averaging. The conclusion is that the large mode volume of the cavity keeps the electric field density at the mirror surfaces low enough to avoid TLS loss.","pith_inferences":["If the drift explanation is correct, an improved averaging scheme—such as interleaved reference tones or faster digitization—should recover a flat internal quality factor versus photon number; such a control measurement would directly test the no-TLS conclusion.","The frequency-independent attenuation of transparent HDPE suggests the same waveguide technology could extend naturally to sub-THz and THz bands, where other low-loss flexible transmission lines are scarce.","Black HDPE as a distributed cold attenuator with infrared blocking could be combined with the copper-powder coating to realize fully absorptive, impedance-matched input lines for millimeter-wave qubit experiments.","Crosstalk suppression by metal-mesh shielding may scale to dense multi-channel arrays, enabling frequency-multiplexed millimeter-wave readout."],"forward_implications":["Dilution refrigerators can be fitted with many dielectric waveguide lines without exceeding thermal budgets, because each anchored line adds only nanowatts to the coldest stages.","Black HDPE waveguides can serve as cold attenuators that also block infrared and thermal photons, simplifying noise engineering at millimeter-wave frequencies.","The demonstrated single-photon sensitivity at around 100 GHz opens the door to millimeter-wave circuit quantum electrodynamics, such as coupling superconducting qubits or cavities at higher photon energies.","The absence of TLS loss in a large-mode-volume cavity implies that millimeter-wave cavities can reach very high coherence without special surface treatments."],"supporting_citations":[{"why":"Establishes that a dielectric strip can carry millimeter waves, grounding the whole waveguide concept.","marker":"[1]"},{"why":"Provides simulated evanescent-field decay and material guidance used here to estimate field confinement of the HDPE waveguide.","marker":"[2]"},{"why":"Demonstrates prior cryogenic use of dielectric waveguides up to 300 GHz and 4.2 K, which this work extends down to 10 mK.","marker":"[4]"},{"why":"Supplies the tapered-transition approach for impedance matching between rectangular waveguide and dielectric waveguide.","marker":"[7]"},{"why":"Provides the cone-shaped coupling scheme used to reach the evanescent portion of the wave in the adapter design.","marker":"[8]"},{"why":"Introduces resistive WR10 tubes for cryogenic attenuation, one of the conditioning options the paper compares to its black-HDPE and copper-coating methods.","marker":"[14]"},{"why":"Supplies the design of a niobium-coated copper Fabry–Pérot cavity that is adapted here to the W-band.","marker":"[16]"},{"why":"Provides the circle-fit algorithm used to extract internal and coupling quality factors from the resonance data.","marker":"[21]"},{"why":"Reviews two-level-system loss and its expected photon-number dependence, which the paper tests against its measured quality factors.","marker":"[23]"}],"fun_headline_variants":["Plastic waveguides enable single-photon cavity Q of 15 million at 10 mK","Mm-wave plastic guides reach Q=15M in single-photon limit at 10 mK","Superconducting cavity Q of 15 million via plastic waveguides at 10 mK","Dielectric waveguides beat TLS: cavity Q 15M at single-photon, 10 mK","Plastic mm-wave guides preserve 15M Q in superconducting cavity at 10 mK"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The no-TLS conclusion rests on attributing the drop in internal quality factor below 100 photons to slow parameter drift during hours-long averaging; if that attribution is wrong, the flatness at higher photon counts would not prove the absence of two-level-system loss.","fun_headline_variants_meta":{"raw":{"variants":["Plastic waveguides enable single-photon cavity Q of 15 million at 10 mK","Mm-wave plastic guides reach Q=15M in single-photon limit at 10 mK","Superconducting cavity Q of 15 million via plastic waveguides at 10 mK","Dielectric waveguides beat TLS: cavity Q 15M at single-photon, 10 mK","Plastic mm-wave guides preserve 15M Q in superconducting cavity at 10 mK"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000712,"raw_usage":{"total_tokens":3184,"prompt_tokens":904,"completion_tokens":2280,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":520,"completion_tokens_details":{"reasoning_tokens":2159}},"tokens_in":520,"tokens_out":2280,"duration_ms":16882,"temperature":1.0,"reasoning_tokens":2159,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T14:32:04.092405+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the same cavity mode's internal quality factor versus photon number with a scheme that eliminates long-term drift, for instance by interleaving a high-power reference with each low-power point or by using faster phase-locked averaging. If the quality factor still falls below 100 photons after drift correction, the claim that two-level systems do not affect the cavity would be falsified.","supporting_citations":[{"cited_title":"Hondros and P","cited_arxiv_id":null,"evidence_quote":"Establishes that a dielectric strip can carry millimeter waves, grounding the whole waveguide concept."},{"cited_title":"Fukuda, Y","cited_arxiv_id":null,"evidence_quote":"Provides simulated evanescent-field decay and material guidance used here to estimate field confinement of the HDPE waveguide."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Demonstrates prior cryogenic use of dielectric waveguides up to 300 GHz and 4.2 K, which this work extends down to 10 mK."},{"cited_title":"Weinzierl, Ch","cited_arxiv_id":null,"evidence_quote":"Supplies the tapered-transition approach for impedance matching between rectangular waveguide and dielectric waveguide."},{"cited_title":"Hofmann, E","cited_arxiv_id":null,"evidence_quote":"Provides the cone-shaped coupling scheme used to reach the evanescent portion of the wave in the adapter design."},{"cited_title":"Greig, Cryogenics 28, 243 (1988)","cited_arxiv_id":null,"evidence_quote":"Introduces resistive WR10 tubes for cryogenic attenuation, one of the conditioning options the paper compares to its black-HDPE and copper-coating methods."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Provides the circle-fit algorithm used to extract internal and coupling quality factors from the resonance data."},{"cited_title":"https://github.com/qkitgroup/qkit,","cited_arxiv_id":null,"evidence_quote":"Reviews two-level-system loss and its expected photon-number dependence, which the paper tests against its measured quality factors."}],"review_version":1}