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This paper predicts that a 2.5-meter cryogenic triangular Sagnac speed meter with power and signal recycling can reach a quantum-noise-limited strain sensitivity of about 3×10^-18 Hz^-1/2 at 1 Hz, provided the end mirrors reach 99.9999% ref

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A dual-recycled triangular Sagnac speed-meter design for a 2.5 m torsion-bar gravitational-wave detector is modeled to reach h≈3×10^-18 Hz^-1/2 at 1 Hz with stable mode matching above 99.5%.

T0 review reviewed 2026-08-04 challenge →

load-bearing objection A coherent optical design study for a compact Sagnac speed meter, but its headline sensitivity is a conditional projection resting on unverified coating technology — worth reviewing, not yet a demonstrated result. the 3 major comments →

arxiv 2510.24780 v4 pith:TINCQ7BA submitted 2025-10-25 physics.ins-det astro-ph.COastro-ph.IMgr-qc

Cryogenic sub-Hz cROss torsion bar detector with quantum NOn-demolition Speed meter (CHRONOS) for gravitational wave detection

Yuki Inoue , Daiki Tanabe , M.Afif Ismail , Vivek Kumar , Mario Juvenal S Onglao III , Ta-Chun Yu This is my paper
classification physics.ins-det astro-ph.COastro-ph.IMgr-qc PACS 95.55.Ym04.80.Nn
keywords gravitational wavessub-hertz detectorsSagnac interferometerspeed meterquantum nondemolitiontorsion-bar antennacryogenic coatingssignal recycling
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

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

The reading

The paper is trying to show that sub-hertz gravitational-wave sensitivity can be achieved on a laboratory scale, in the band where ordinary ground-based detectors are disabled by seismic noise and space detectors cannot reach. Its central proposal is a triangular Sagnac 'speed meter', which reads out the velocity of the torsion-bar test masses rather than their displacement, so the radiation-pressure back-action that normally ruins low-frequency sensitivity cancels. The authors provide a complete optical design—mirror curvatures, recycling cavities, control sidebands, and an optimized working point—and calculate that the device would reach roughly 3×10^-18 per root hertz of strain at 1 Hz, limited by quantum noise. If that projection holds, a 2.5-meter cryogenic facility would be a genuine quantum-noise-limited sub-hertz gravitational-wave observatory and a prototype for longer-baseline versions.

Core claim

The central claim is that a dual-recycled triangular Sagnac speed meter is stable and quantum-noise-limited at the 2.5-meter scale. With optimized mirror curvatures, the cavity eigenmodes are stable with a round-trip Gouy phase near 153°, mode-matching efficiencies above 99.5%, and a finesse of about 3.1×10^4. At the working point—power-recycling detuning of -85°, signal-recycling at resonance, and a homodyne angle near 46°—the predicted quantum-limited strain noise is h ≈ 3×10^-18 Hz^-1/2 at 1 Hz. The speed-meter topology is the essential ingredient: because the signal is read as a difference in propagation speed between the two circulating beams rather than a displacement, radiation-pressu

What carries the argument

The load-bearing element is the triangular Sagnac ring cavity used as a speed meter: light circulates clockwise and counterclockwise, and the gravitational-wave signal appears as a difference in their propagation speeds rather than as an accumulated mirror-displacement phase. That velocity readout is what cancels radiation-pressure noise at low frequency. Around this ring, a power-recycling cavity (deliberately detuned by -85°) sets the circulating power and shapes the low-frequency quantum noise, while a signal-recycling cavity at resonance rotates the readout quadrature nearly uniformly. The named quantities that carry the design are the round-trip Gouy phase (the total transverse phase ad

Load-bearing premise

The whole projection rests on a coating that has not yet been demonstrated: an end mirror that is simultaneously 99.9999% reflective and has an effective mechanical loss angle of 1e-5 or less at 10 K, combining low optical absorption with low mechanical dissipation in one dielectric stack.

What would settle it

Measure the optical absorption and mechanical loss of candidate coating stacks at 10 K. If the resulting ring-cavity finesse is well below 3.1×10^4, or if the measured coating Brownian noise in the 1-10 Hz band lies above the predicted quantum-noise curve, the projected h≈3×10^-18 Hz^-1/2 at 1 Hz is not reachable. A direct check of the optics is to build the 2.5-meter ring with the specified mirrors and verify mode-matching efficiency above 99.5% and a clockwise/counterclockwise power asymmetry below 3×10^-5.

Watch this falsifier. Get emailed when new claim-graph text bears on it.

If this is right

  • Sub-hertz gravitational-wave science could be done on a tabletop scale, bridging the band between ground-based detectors and space missions.
  • At the projected sensitivity, the detector could see intermediate-mass black-hole binaries out to roughly 271 Mpc, a ten-year stochastic-background level of Ω_GW≈4.7×10^-4 at 2.15 Hz, and prompt gravity-gradient signals from nearby earthquakes.
  • The design principle—using power-recycling detuning rather than signal-recycling detuning as the main low-frequency quantum-noise knob—can be carried over to longer-baseline cryogenic detectors.
  • Cryogenic coating technology becomes the decisive path: achieving 99.9999% reflectivity with an effective loss angle of 1e-5 or less at 10 K would realize the predicted finesse and quantum-limited sensitivity.
  • The same optical layout, with detuning and homodyne angle readjusted, could be reshaped for higher-frequency observations, making the facility a versatile testbed.

Where Pith is reading between the lines

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

  • Editorial inference: the least-discussed load-bearing constraint may be the clockwise/counterclockwise circulating-power balance; a real instrument must keep that asymmetry below 3×10^-5 to preserve the speed-meter's back-action cancellation, and this is independently testable from the mode-matching measurement.
  • Editorial inference: the paper's emphasis on power-recycling detuning suggests a general recipe for compact sub-hertz interferometers—speed-meter topology for back-action cancellation plus intentional PRC detuning for low-frequency noise shaping—that could be applied to other torsion-bar designs.
  • Editorial inference: if the 2.5-meter predictions hold, scaling the same optical design to longer arms should allow the detector to trade low-frequency sensitivity for bandwidth by adding a small signal-recycling detuning, potentially creating a ground-based instrument that connects continuously to the space-based band.
  • Editorial inference: the sensitivity projection effectively predicts a specific finesse (≈3.1×10^4) and a specific coating Brownian-noise floor; both are directly measurable in a prototype before the full quantum-noise performance is claimed.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

3 major / 5 minor

Summary. The paper presents the optical design and sensitivity modeling of the 2.5 m CHRONOS detector, a triangular Sagnac speed-meter interferometer with power and signal recycling for sub-hertz gravitational-wave detection. The authors use ABCD-matrix analysis and Finesse3 simulations to obtain stable cavity eigenmodes with mode-matching efficiencies above 99.5%, a ring-cavity finesse of about 3.1e4, and a round-trip Gouy phase near 153 degrees. They then compute a quantum-noise-limited strain sensitivity of h ~ 3e-18 Hz^{-1/2} at 1 Hz, optimized by PRC detuning, SRC resonance, and a homodyne angle of about 46 degrees, assuming an ETM reflectivity of 99.9999% and an effective coating loss angle of 1e-5 at 10 K. The paper also describes control sidebands, locking ports, and a preliminary technical-noise budget including coating Brownian, torsion-bar, and seismic noise.

Significance. If the assumed coating parameters can be realized, this is a valuable design study: it shows that a laboratory-scale dual-recycled Sagnac speed meter can have stable, high-finesse eigenmodes and a quantum-noise-limited sub-hertz sensitivity, making it a plausible testbed for future long-baseline cryogenic detectors. The paper's strengths include a complete optical-element listing, an explicit control-sideband and locking scheme, independent ABCD and Finesse3 cross-checks of the stability calculation, and candid statements about open coating issues. However, the headline sensitivity number is a conditional projection, not a demonstrated detector capability, because it relies on an unverified combination of high reflectivity, negligible absorption, and low cryogenic mechanical loss, and because the intensity-noise contribution to the plotted total-sensitivity curves is deferred to an unpublished reference.

major comments (3)
  1. [Sec. VI B; Table V; Table VI; Appendix A] The central sensitivity claim h ~ 3e-18 Hz^{-1/2} at 1 Hz depends on the simultaneous assumptions R_ETM = 99.9999%, φeff_c ≤ 1e-5 at 10 K, and A ≈ 0. The manuscript itself states that PECVD SiN/SiO2 and SiON coatings have suitable mechanical loss but insufficient optical absorption, and that LPCVD coatings are only 'currently being investigated' (Ref. [41], unpublished). Appendix A and Table VI list 'A ≈ 0' rather than measured absorption values, and Figs. 3-4 show that reducing the effective interferometer reflectivity degrades QND suppression at low frequencies. Consequently, the numerical sensitivity is not a demonstrated capability but a projection conditional on coating R&D. Please either provide supporting measured coating data or a realistic loss model, or explicitly reframe the abstract, Eq. (25), and conclusion as a conditional design projection tied to a specified coating miles
  2. [Figs. 5, 8, 11, 14; Sec. VI A; Ref. [34]] The total-quantum-noise spectra in Figs. 5, 8, 11, and 14 include technical noise, with the text repeatedly noting 'The intensity noise is calculated elsewhere [34]'. Reference [34] is an unpublished in-preparation work, so the intensity-noise model, its parameters, and its coupling to the readout are not available for checking. This makes the plotted total sensitivity curves non-reproducible. Include a self-contained intensity-noise model (equations and parameters) in the manuscript, or state clearly that the quantitative sensitivity plots are quantum noise plus coating/suspension/seismic noise only and that intensity noise is omitted.
  3. [Sec. V A, Eq. (19)] The QND condition is reduced to |Δη/η| < 3e-5, and this tolerance is stated to be 'fully satisfied' by the achieved mode-matching efficiency η ~ 99.5%. However, no explicit error budget or misalignment study is provided to show that the CW/CCW coupling asymmetry remains below this bound under realistic mirror alignment errors, thermal deformation, or asymmetric absorption. Because Eq. (18) is the formal basis for radiation-pressure cancellation in the speed-meter readout, the paper should include a tolerance analysis, a Monte-Carlo/random-misalignment estimate, or an explicit statement that the asymmetry bound is an assumed design condition rather than a demonstrated result of the current ABCD optimization.
minor comments (5)
  1. [Abstract] Typo 'Assumming' should be 'Assuming'; also 'mode-matching efficiencies above 99.5' should read '99.5%'.
  2. [Sec. VI D and Table V] The text states that CHRONOS operates at 'the resonant condition (φs = 90° in our convention)', while Table V lists φs = 0°. Given the phase-convention discussion, this is confusing and likely a typo; please clarify the convention consistently.
  3. [Appendix A] Appendix A is described as a complete list of optical elements, but power transmissivity and absorption values are omitted and replaced by the relation T = 1 - R - A with 'A ≈ 0'. Since absorption is a key assumption for the sensitivity result, state this approximation prominently at the start of Appendix A and, if possible, give the separate T and A values for the main optics.
  4. [Refs. [34] and [41]] Both references are placeholders with 'Title of the unpublished work (in preparation)'. Unpublished references cannot be checked. Update them if versions are available at revision, or remove reliance on them by including the needed material in the text.
  5. [Appendix B1] The notation 'ωETM' in Eq. (B1) is not explicitly defined; it is described as a geometric factor approximately proportional to the beam radius, but a definition or explicit expression would help reproducibility.

Circularity Check

0 steps flagged

No material circularity: the central sensitivity is a conditional design calculation from explicitly stated optical parameters; only minor in-preparation self-citations appear.

full rationale

The central derivation chain is self-contained against the paper's stated assumptions. The quantum-noise sensitivity h ≈ 3 × 10^-18 Hz^-1/2 at 1 Hz (Eq. 25) follows from the Buonanno-Chen two-photon input-output relation (Eqs. 20-24), with the parameters in Table V treated as design choices rather than as fitted values. Mode-matching efficiencies are computed from ABCD-matrix and Finesse3 analyses (Eqs. 8-13) and then optimized; reporting the optimized value is a design result, not a prediction forced by the inputs. The ETM reflectivity R = 99.9999% and coating loss φeff_c ≤ 1e-5 are explicitly assumptions: Table V, Table VI, Section VI B ('To achieve the CHRONOS sensitivity goal, the total effective coating loss angle must satisfy φeff_c ≤ 10^-5 at cryogenic temperatures, while maintaining a reflectivity of R ∼ 99.9999%'), and Appendix A ('with A ≈ 0'). The paper itself flags that PECVD coatings have suitable mechanical loss but insufficient absorption and that LPCVD coatings are only 'currently being investigated' (Section VI B, with [41] in preparation), so the headline number is a conditional projection rather than a claimed demonstrated capability. Self-citations and in-preparation items ([7] companion design paper for science reach; [34] intensity noise; [41] LPCVD absorption study) are same-team, but they are not the mechanism that produces the central quantum-noise calculation; the calculation would stand with the same stated assumptions. No equation reduces to another by construction, no fitted parameter is renamed as a prediction, and no uniqueness theorem is imported from the authors. The only caveat is the coating-technology assumption, which is an input, not a circular output.

Axiom & Free-Parameter Ledger

12 free parameters · 7 axioms · 0 invented entities

The central design rests on standard Gaussian-optics and quantum-noise formalisms, but the headline sensitivity assumes unproven low-loss high-reflectivity coatings and uses optimized operating parameters. No new physical entities are introduced.

free parameters (12)
  • ETM/CM mirror curvature radii = R_ETM=2.69 m, R_CM=0.141 m, R_PRM3=7.02 m, R_SRM2=7.15 m
    Optimized by ABCD analysis to maximize mode-matching efficiency; Table VI.
  • PRC detuning phase φp = -85°
    Scanned to balance shot noise and radiation-pressure noise at 1 Hz; Table V, Section VI C.
  • Homodyne angle ζ = 46°
    Optimized by scan; balances radiation-pressure suppression and shot noise; Section VI E.
  • SRC detuning phase φs = 0° (resonant)
    Set to resonant condition; detuning degrades QND cancellation; Table V, Section VI D.
  • Recycling mirror reflectivities = Rp=0.9, Rs=0.5
    Assumed to set PRC and SRC cavity bandwidths; Table V.
  • ETM reflectivity = 99.9999%
    Critical high-reflectivity assumption at 10 K; not demonstrated; Tables V and VI.
  • Coating effective mechanical loss angle φeff_c = ≤1e-5
    Assumed target for cryogenic coating; sets coating Brownian noise floor; Section VI B.
  • Internal optical loss L_int = <1e-5 (10 ppm)
    Assumed from high-quality dielectric coatings; Section V A.
  • Coupling asymmetry requirement |Δη/η| = <3e-5
    Derived from finesse with an added safety margin; Eq. (19).
  • Cavity lengths and sideband frequencies = Lring=5.08 m, Lsrc=5.08 m, Lprc=7.62 m; f1=29.5 MHz, f2=58.98 MHz
    Chosen to reproduce LIGO resonant/anti-resonant recycling conditions at 2.5 m scale; Section IV A.
  • Input and circulating power = Pin=1 W, Parm=444 W
    Input power is assumed; circulating power is a model output from the recycling design; Table V.
  • Geometrical coupling factor η = 0.936
    Derived from bar dimensions and moment-of-inertia ratio; Table V.
axioms (7)
  • standard math Gaussian-beam ABCD formalism and cavity stability criterion 0<g1g2<1 correctly describe the optical eigenmodes.
    Invoked throughout Section V to compute eigenmodes, Gouy phase, and mode matching.
  • domain assumption The Buonanno-Chen two-photon quantum-noise formalism applies to this Sagnac speed-meter interferometer.
    Used in Section VI A to derive the input-output relation and quantum-noise spectral density.
  • domain assumption The torsion-bar angular response follows Eq. (5) with an ideal thin-rod coupling factor and long-wavelength antenna patterns.
    Sets the conversion from GW strain to angular displacement; Section II.
  • ad hoc to paper Speed-meter topology cancels radiation-pressure noise provided the CW/CCW coupling asymmetry satisfies |Δη/η|<3e-5.
    Threshold includes a safety margin beyond the finesse-derived condition; Eq. (18)-(19).
  • ad hoc to paper Coating technology with R_ETM=99.9999% and φeff_c≤1e-5 at 10 K is achievable.
    The sensitivity projection explicitly assumes this; Section VI B acknowledges LPCVD coatings are still under investigation.
  • domain assumption ASGRAF ground-displacement data plus a LIGO-like pre-isolation and multi-stage pendulum suspension represent the seismic coupling.
    Used in Appendix B 3 to model seismic noise.
  • standard math Coating Brownian noise is described by the half-infinite substrate model and the fluctuation-dissipation theorem.
    Appendix B 1; standard in coating thermal noise estimates.

reviewed 2026-08-04 · how reviews work

0 comments
Cite this review

Pith. "Pith review of Cryogenic sub-Hz cROss torsion bar detector with quantum NOn-demolition Speed meter (CHRONOS) for gravitational wave detection." pith.science (2026). https://pith.science/paper/TINCQ7BA

@misc{pith2026251024780,
  author       = {Pith},
  title        = {Pith review of: Cryogenic sub-Hz cROss torsion bar detector with quantum NOn-demolition Speed meter (CHRONOS) for gravitational wave detection},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/TINCQ7BA}},
  note         = {Machine review of arXiv:2510.24780}
}
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abstract

We present the optical design and sensitivity modeling of the Cryogenic sub-Hz cROss torsion-bar detector with quantum NOn-demolition Speed meter (CHRONOS), a triangular Sagnac speed-meter interferometer incorporating power and signal recycling. Using ABCD-matrix analysis and \textsc{Finesse3} simulations, we obtain stable optical eigenmodes with mode-matching efficiencies above 99.5%. The optimized configuration achieves a quantum-noise-limited strain sensitivity of $h \simeq 3\times10^{-18},\mathrm{Hz^{-1/2}}$ at 1 Hz, with a ring-cavity finesse of $\mathcal{F}\simeq3.1\times10^{4}$ and a round-trip Gouy phase of $\psi\approx153^{\circ}$. The low-frequency quantum noise is primarily governed by the power-recycling cavity detuning, while the signal-recycling cavity produces an approximately uniform quadrature rotation. An optimal homodyne angle of $\zeta\simeq46^{\circ}$ provides the best sensitivity near 1 Hz. Assuming an end-mirror reflectivity of $R_{\mathrm{ETM}}=99.9999%$ at 10 K, CHRONOS can achieve quantum-noise-limited performance on a laboratory scale. Its projected science reach includes intermediate-mass black-hole binaries out to approximately $271,\mathrm{Mpc}$, a 10-year stochastic-background sensitivity of $\Omega_{\mathrm{GW}}\simeq4.7\times10^{-4}$ at $2.15,\mathrm{Hz}$, constraints on Yukawa-type deviations from Newtonian gravity, and prompt gravity-gradient signals from nearby earthquakes.

Figures

Figures reproduced from arXiv: 2510.24780 by Daiki Tanabe, M.Afif Ismail, Mario Juvenal S Onglao III, Ta-Chun Yu, Vivek Kumar, Yuki Inoue.

Figure 1
Figure 1. Figure 1: Schematic of the bar-shaped test masses. Each bar has [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Schematic optical layout of the CHRONOS 2.5 m test facility. [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Comparison of shot noise and radiation-pressure noise fo [PITH_FULL_IMAGE:figures/full_fig_p013_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Radiation-pressure noise at low frequencies, illustrating d [PITH_FULL_IMAGE:figures/full_fig_p013_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Total quantum-noise spectra including shot noise, radiat [PITH_FULL_IMAGE:figures/full_fig_p014_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Impact of PRC detuning on shot noise. The variation is expla [PITH_FULL_IMAGE:figures/full_fig_p014_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Impact of PRC detuning on radiation-pressure noise. At t [PITH_FULL_IMAGE:figures/full_fig_p015_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: Total quantum-noise spectra including shot noise, radiat [PITH_FULL_IMAGE:figures/full_fig_p015_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: Impact of SRC detuning on shot noise. Detuning mixes amplit [PITH_FULL_IMAGE:figures/full_fig_p016_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: Impact of SRC detuning on radiation-pressure noise. Th [PITH_FULL_IMAGE:figures/full_fig_p017_10.png] view at source ↗
Figure 11
Figure 11. Figure 11: Total quantum-noise spectrum including shot noise, rad [PITH_FULL_IMAGE:figures/full_fig_p017_11.png] view at source ↗
Figure 12
Figure 12. Figure 12: Dependence of shot noise on the homodyne detection an [PITH_FULL_IMAGE:figures/full_fig_p018_12.png] view at source ↗
Figure 13
Figure 13. Figure 13: Radiation-pressure noise as a function of homodyne ang [PITH_FULL_IMAGE:figures/full_fig_p018_13.png] view at source ↗
Figure 14
Figure 14. Figure 14: Total quantum-noise spectra for various homodyne an [PITH_FULL_IMAGE:figures/full_fig_p019_14.png] view at source ↗

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Forward citations

Cited by 7 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Science of Cryogenic sub-Hz cROss torsion bar detector with quantum NOn-demolition Speed meter (CHRONOS)

    astro-ph.IM 2026-04 unverdicted novelty 8.0

    CHRONOS is a proposed cryogenic torsion-bar detector with quantum non-demolition speed-meter readout targeting 10^{-18} strain sensitivity at 2 Hz to open the sub-Hz gravitational-wave window from the ground.

  2. Noise budget of Cryogenic sub-Hz cROss torsion bar detector with quantum NOn-demolition Speed meter (CHRONOS)

    physics.ins-det 2026-04 unverdicted novelty 6.0

    CHRONOS targets strain sensitivity of 10^{-18} Hz^{-1/2} at 2 Hz via cryogenic cross torsion-bar design and speed meter, with simulations showing competitive low-frequency performance and 2.92-6.90 s faster earthquake...

  3. Instrumental development for Cryogenic sub-Hz cROss torsion bar detector with quantum NOn-demolition Speed meter (CHRONOS)

    astro-ph.IM 2026-04 unverdicted novelty 6.0

    CHRONOS is a proposed cryogenic sub-Hz torsion-bar speed-meter detector targeting 10^{-18} Hz^{-1/2} strain sensitivity at 2 Hz for IMBH mergers and stochastic GW backgrounds.

  4. Improving calibration accuracy with torque coupled gravity field calibrator for sub-Hz gravitational wave observation in CHRONOS

    gr-qc 2026-02 conditional novelty 6.0

    A torque-coupled gravity calibrator for CHRONOS is calculated to give a calibration SNR density of 4.25e3 at 1 Hz with 0.24% fractional systematic uncertainty.

  5. Prospects for Observing Gravity-gradient Noise and Earthquake Gravity Signals with CHRONOS

    physics.ins-det 2026-06 unverdicted novelty 5.0

    CHRONOS is projected to detect prompt gravitational signals from Mw 5.2 earthquakes within ~90 km (SNR ~3.62 at 40 km in sub-Hz band) while Rayleigh-wave Newtonian noise dominates below ~0.5 Hz.

  6. Probing Yukawa Gravity with Modulated Newtonian Cancellation in the CHRONOS Detector

    gr-qc 2026-04 unverdicted novelty 5.0

    Torsion-bar detector with differential mass cancellation reaches |α_Y| = 2.4×10^{-5} at λ = 8 m for Yukawa gravity deviations, limited by source-mass geometry uncertainties after ~26 hours.

  7. Noise budget of Cryogenic sub-Hz cROss torsion bar detector with quantum NOn-demolition Speed meter (CHRONOS)

    physics.ins-det 2026-04 conditional novelty 5.0

    Simulated noise budget for the proposed CHRONOS sub-Hz detector projects competitive sensitivity near 2 Hz and multi-second earthquake early-warning lead times within 40 km.

Reference graph

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This paper was first reviewed by deepseek-v4-flash on August 4, 2026.