{"id":"d762de81-25fe-42fb-a9d2-a2957b6fad66","arxiv_id":"2607.08585","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":6.5,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"Gate-defined JJ sensor in magic-angle twisted graphene resolves multi-vortex dynamics, with rates saturating below 80 mK suggestive of macroscopic quantum tunneling of individual Pearl vortices.","lead":"A Josephson junction in twisted graphene detects single vortices via Fraunhofer shifts and telegraph noise in voltage. Temperature-dependent rates show thermal creep above 100 mK and saturation below 80 mK, interpreted as macroscopic quantum tunneling of Pearl vortices.","discovery_kind":"extension","skeptic_critique":{"model":"grok-4.5","headline":"The multi-vortex voltage-to-state mapping that supplies the separate entry/exit rates is the softest link in the thermal-to-quantum claim.","rationale":"The Reader correctly isolates the voltage-to-vortex mapping (Sec. IV A–B, Fig. 1(d)) as the weakest assumption required for the strongest claim. My stress-test confirms that this mapping is not merely a presentational convenience: it is the sole justification for separating the four rates whose T-dependence is then interpreted as thermal-to-quantum crossover. The experimental pipeline (digitization, bi-exponential fits, bandwidth correction) is carefully documented and the data are public, so the concern is not about data quality but about the physical interpretation that converts those data into entry/exit rates. Because an independent re-analysis that discards the B0/V(B) labels can be performed with the released traces, the concern is falsifiable and does not warrant a stronger rejection. Hence the Reader’s CONDITIONAL verdict is left unchanged.","tokens_in":21526,"tokens_out":724,"duration_ms":6904,"concrete_test":"Re-analyze the entire set of 4-hour Vd(t) traces at every temperature using only the raw two-level waiting-time histograms, without any a-priori assignment of “nv” versus “v” based on B0(T) or V(B). If the resulting temperature dependence of the two (or four) rates still shows a clear plateau below ~80 mK followed by an activated rise above ~100 mK, the MQT claim is robust to the mapping; if the plateau disappears or the rates become non-monotonic once the labels are removed, the multi-vortex assignment is load-bearing and the claim weakens.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The central claim (thermal activation above ~100 mK, saturation suggestive of MQT below ~80 mK) rests on the four rates Γ_fast_nv, Γ_slow_v, Γ_slow_nv, Γ_fast_v extracted from the two clusters in the τ_nv–τ_v correlation plots (Figs. 3c, 5c). Those clusters are assigned to “pristine lead + nearby fluctuating vortex” versus “distant quasi-stationary vortex + nearby fluctuating vortex” solely by (i) the relative position of B* = 2 mT with respect to the fitted B0(T) (Fig. 2f) and (ii) the sign of the slope of V(B) at B* (Fig. 4b). Both ingredients are model-dependent: B0 is obtained by fitting the main lobe of the Fraunhofer pattern to the weakly-screening formula (Eq. 2) with an effective width W_eff(T) that itself increases with T, and the voltage-level ordering is inferred from a calculated vortex-induced phase shift of ~0.4 mT. If either the B0(T) trajectory or the V(B) slope assignment is incorrect, the four rates are mis-labeled and the Arrhenius/MQT interpretation of their temperature dependence collapses. The paper itself notes that around T ≈ 45 mK (where B* ≈ B0) the signal becomes unusable, underscoring the sensitivity of the mapping.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.5","summary":"The manuscript reports a gate-defined Josephson junction fabricated in magic-angle twisted four-layer graphene that functions as a single-vortex sensor. Shifts in the Fraunhofer pattern of Ic(B) and telegraph noise in voltage time traces Vd(t) are interpreted as multi-vortex processes in which fast fluctuations of nearby Pearl vortices are modulated by quasi-stationary distant vortices. Waiting-time analysis of the two distinct clusters in the τnv–τv correlation plots yields four rates (Γfast_nv, Γslow_v, Γslow_nv, Γfast_v). Their temperature dependence between 7 mK and 120 mK is fitted to Arrhenius activation above ≈100 mK and saturates below ≈80 mK; the saturation is presented as evidence for a crossover to macroscopic quantum tunneling of vortices. Barriers U/kB of a few kelvin and actions S/ℏ ≈ 24–27 are extracted and shown to be consistent with the free-energy landscape of a Pearl vortex in a weakly screening strip.","tokens_in":21949,"tokens_out":1346,"duration_ms":18561,"significance":"If the multi-vortex assignment and the thermal-to-quantum interpretation hold, the work supplies a rare transport-based probe of individual Pearl-vortex entry/exit events and their rates in a tunable 2D superconductor. The careful post-processing pipeline (Yuzhelevski digitization, Freedman–Diaconis binning, bi-exponential fits, finite-bandwidth correction) and the public data release strengthen reproducibility. Consistency of the extracted U and S with the theoretical edge-barrier landscape of Ref. [63] and with independent estimates of ρs and λL constitutes a non-trivial check. Observation of macroscopic quantum tunneling of vortices would be of broad interest for quantum creep and for vortex-based superconducting electronics.","major_comments":[{"comment":"Sec. IV A–B and Figs. 3(c), 5(c): the four rates that underwrite the thermal/MQT claim are obtained only after the two clusters in the τnv–τv plots are assigned to “pristine lead + nearby fluctuating vortex” versus “distant quasi-stationary vortex + nearby fluctuating vortex.” That assignment rests on (i) the relative position of the fixed measurement field B* = 2 mT with respect to the fitted first zero B0(T) (Fig. 2f) and (ii) the sign of the slope of V(B) at B* (Fig. 4b). Both ingredients are model-dependent: B0 is extracted by fitting Eq. (2) with a temperature-dependent effective width Weff(T) that itself increases from 1.16 µm to 1.5 µm, and the voltage-level ordering is inferred from a calculated vortex-induced phase shift of ~0.4 mT. The paper notes that the signal becomes unusable near T ≈ 45 mK where B* ≈ B0, underscoring the sensitivity of the mapping. Alternative assignments","section":null},{"comment":"Sec. V and Eqs. (3)–(4): the claim of a “sharp transition” to macroscopic quantum tunneling is based on the saturation of the four rates below ≈80 mK. While the data are consistent with a crossover from thermal activation to quantum tunneling, the temperature window is narrow, the attempt frequency ν0 is taken from the literature range rather than measured, and no independent signature (e.g., magnetic-field dependence of the action or a clear T0 matching condition) is provided. A more cautious phrasing—“suggestive of a crossover”—together with an explicit discussion of alternative saturation mechanisms (e.g., residual heating, detector bandwidth, or multi-vortex pinning) would better match the strength of the evidence.","section":null},{"comment":"Sec. III and Fig. 2(f): the observed decrease of B0 with temperature is outside the generic weakly-screening model of Ref. [49] and is attributed to a speculative temperature-dependent suppression of superfluid density near the junction. Because B0(T) directly controls the voltage-to-state mapping used for all rate extractions, a more quantitative model (or at least a systematic uncertainty band on Weff(T)) is needed; otherwise the temperature evolution of the rates inherits an uncontrolled systematic.","section":null}],"minor_comments":[{"comment":"Fig. 1(c) and throughout: the top axis is labeled ΦW/Φ0 while the text uses ΦW = B W^{2}; a consistent definition and a brief reminder of the weakly-screening flux-to-field conversion would help readers unfamiliar with Ref. [49].","section":null},{"comment":"Appendix C: the finite-bandwidth correction formulae (C2)–(C3) are taken from Ref. [70]; stating the measured Γdet = 1098(93) Hz already in the main text (rather than only in the appendix) would make the rate values easier to assess.","section":null},{"comment":"Sec. II A: the argument that the junction is short (W ≲ 2ξJ) is clear, yet a short numerical table of the estimated lengths (ξ, λL, Λ, ξJ, W) would make the conclusion more immediately verifiable.","section":null},{"comment":"Several figure panels contain residual OCR artifacts (m¯ for mT, Cou¯ts, etc.); these should be cleaned before final production.","section":null},{"comment":"The relation of the present multi-vortex analysis to the earlier single-vortex reports [46,47] could be stated more explicitly in the introduction so that the incremental contribution is transparent.","section":null}],"recommendation":"major_revision","confidential_remarks":"The manuscript is a natural and carefully executed extension of the authors’ own prior works [46,47]. The multi-vortex interpretation is the only load-bearing interpretive step; if the authors can strengthen or more thoroughly justify the voltage-to-state mapping, the paper would be suitable for a high-profile condensed-matter journal. The data-release link is a positive feature that should be retained."},"author_rebuttal":null,"desk_editor":{"model":"grok-4.5","letter":"The new piece here is not the JJ-as-vortex-sensor idea or the low-T rate plateau—those were already in the authors’ prior notes—but the systematic separation of multi-vortex processes. They use τ_nv–τ_v correlation plots and bi-exponential histograms to pull four distinct entry/exit rates out of the same long voltage traces, then track them from 7 mK to 120 mK. That is real experimental work, and the data-reduction pipeline (Yuzhelevski digitization, Freedman–Diaconis binning, finite-bandwidth correction) is cleanly documented with public data and code.\n\nWhat they do well is keep the central claim proportionate. The abstract and discussion say “suggestive of” a thermal-to-MQT crossover, not “we prove.” The high-T Arrhenius rise and the low-T saturation of S/ℏ ≈ 24–27 are standard vortex-creep phenomenology; the extracted U/kB ~ 2–2.6 K and the consistency check against the Stejic free-energy landscape and ρs ≈ 0.8 K look reasonable. They also correctly rule out long-junction Josephson-vortex metastability by showing the phase-core size exceeds W.\n\nThe soft spot is exactly the one the stress-test flags: the assignment of the two clusters (and therefore the four rates) to “pristine + nearby fluctuating vortex” versus “distant quasi-stationary vortex + nearby fluctuating vortex.” That mapping leans on the fitted B0(T) trajectory (which requires an effective width that grows with T) and on the sign of the V(B) slope at the fixed measurement point B* = 2 mT. Around 45 mK the signal dies because B* ≈ B0, which underscores the sensitivity. If that map is wrong the labels on Γ_nv and Γ_v swap and the Arrhenius/MQT story has to be re-read. It is not circular—U and S are extracted from the rates and only later compared with theory—but it is interpretive. The paper is honest about the interpretation; it does not hide the model dependence.\n\nThis is for people who care about single-defect transport probes and 2D vortex creep. The math and citation pattern are solid; the free parameters (ν0, vortex positions, Weff(T)) are the usual ones in this literature. I would send it to referees. They will push on the voltage-to-state map and on independent confirmation of the plateau, which is fair. I would cite the rate-extraction method and the public data set.","headline":"Solid multi-vortex rate analysis on a real device; the thermal-to-MQT claim is carefully hedged and rests on a model-dependent voltage-to-state map that is the main soft spot, not a collapse.","tokens_in":22564,"tokens_out":647,"would_cite":true,"duration_ms":6961,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.5","headline":"A Josephson junction in twisted graphene tracks single vortices switching from thermal creep to quantum tunneling below ~80 mK.","keywords":["Pearl vortices","Josephson junction sensor","telegraph noise","vortex creep","macroscopic quantum tunneling","magic-angle twisted graphene","Fraunhofer pattern","thin-film superconductivity"],"falsifier":"If the low-temperature saturation of rates disappeared when the same device is remeasured with a different fixed field B* or with an independent vortex-imaging technique that confirms the absence of distant trapped vortices, the multi-vortex interpretation and the quantum-tunneling claim would both be undermined.","tokens_in":22452,"feed_emoji":"🌀","tokens_out":814,"duration_ms":7728,"temperature":0.7,"pith_summary":"The authors build a gate-defined Josephson junction in magic-angle twisted four-layer graphene and use it as a local sensor for individual Pearl vortices in the superconducting leads. Vortex entry or exit shifts the Fraunhofer pattern of the junction critical current; the same events appear as telegraph noise in the junction voltage when the bias is held fixed. By separating two distinct timescales in the voltage traces—fast fluctuations near the junction and slower distant vortices that reshape the barriers—they extract entry and exit rates as a function of temperature from 7 mK to 120 mK. Above roughly 100 mK the rates follow thermal activation over barriers of a few kelvin; below about 80 mK the rates saturate, which the authors interpret as a crossover to macroscopic quantum tunneling of vortices. The result turns a bulk, ensemble phenomenon into a single-vortex, transport-based measurement and supplies concrete numbers for barriers, attempt frequencies and tunneling actions in a two-dimensional superconductor.","feed_headline":"Single vortices switch from creep to quantum tunneling","feed_subtitle":"A Josephson sensor in twisted graphene reads entry and exit rates down to 7 mK","key_machinery":"The gate-defined Josephson junction as single-vortex sensor: a vortex in a lead alters the phase difference across the junction, shifting the Fraunhofer pattern of Ic(B) and thereby switching the junction between superconducting and dissipative voltage levels at fixed bias, which appears as telegraph noise whose waiting times yield the dynamical rates.","core_discovery":"Measurements of Ic(B) and V(t) in a weak-leads Josephson device reveal multi-vortex processes in which fast nearby fluctuations are modulated by quasi-stationary distant vortices; the temperature dependence of the extracted rates shows thermal activation above ~100 mK and saturation below ~80 mK that the authors attribute to macroscopic quantum tunneling of Pearl vortices.","pith_inferences":["The ability to gate-tune the superfluid density continuously suggests a route to map how the thermal-to-quantum crossover temperature scales with barrier height in a single sample.","Because the sensor is purely transport-based, the same protocol could be applied to other two-dimensional superconductors where scanning probes are harder to implement.","If the distant quasi-stationary vortices can themselves be manipulated by local gates, the device becomes a controllable multi-vortex register rather than a passive detector."],"forward_implications":["Single-vortex entry and exit rates can be tracked versus carrier density, magnetic field and temperature in the same device.","Edge barriers of a few kelvin and tunneling actions S/ℏ ≈ 24–27 are now measured quantities for Pearl vortices in twisted graphene.","The same sensor architecture can be integrated into superconducting circuits that use or control individual vortices.","The observed crossover temperature (~80–100 mK) sets a practical bound between classical creep and quantum motion in this material."],"fun_headline_variants":["Vortices switch from thermal creep to quantum tunneling","Josephson sensor tracks multi-vortex rates to 7 mK","Twisted graphene vortices enter quantum tunneling regime","Fast fluctuations reveal vortex quantum tunneling below 80 mK","Creep yields to macroscopic quantum tunneling of vortices"],"cache_read_input_tokens":16512,"weakest_assumption_plain":"The mapping of distinct voltage levels and waiting-time clusters onto specific multi-vortex configurations (pristine lead versus distant trapped vortex) depends on the relative position of the measurement field to the first Fraunhofer zero and on calculated phase shifts.","fun_headline_variants_meta":{"raw":{"variants":["Vortices switch from thermal creep to quantum tunneling","Josephson sensor tracks multi-vortex rates to 7 mK","Twisted graphene vortices enter quantum tunneling regime","Fast fluctuations reveal vortex quantum tunneling below 80 mK","Creep yields to macroscopic quantum tunneling of vortices"]},"model":"grok-4.5","effort":"low","cost_usd":0.00572,"raw_usage":{"total_tokens":1516,"prompt_tokens":748,"num_sources_used":0,"completion_tokens":79,"cost_in_usd_ticks":57200000,"prompt_tokens_details":{"text_tokens":748,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":689,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":748,"tokens_out":79,"duration_ms":5966,"temperature":1.0,"reasoning_tokens":689,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-10T04:47:00.824261+00:00","model_set":{"reader":"grok-4.5"},"falsifier":"If the low-temperature saturation of rates disappeared when the same device is remeasured with a different fixed field B* or with an independent vortex-imaging technique that confirms the absence of distant trapped vortices, the multi-vortex interpretation and the quantum-tunneling claim would both be undermined.","supporting_citations":[],"review_version":1}