Pith. sign in

REVIEW 10 references

Unusual crosstalk in coincidence measurement searches for quantum degeneracy

T0 review · reviewed 2026-08-12 · deepseek-v4-flash

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗ Review JSON

Pith's one-line read Weak crosstalk between the start and stop detector channels creates a false antibunching dip in coincidence measurements, even when the electron source has no Coulomb or Pauli interactions, so claimed quantum-degeneracy signals below 0.1%…

desk verdict Real and important crosstalk mechanism for false antibunching dips, but the model equation as printed cannot reproduce the claimed 6.1% dip and needs correction before the quantitative claim can be trusted. read the letter →

arxiv 2411.13863 v1 pith:EQYBIGYG submitted 2024-11-21 quant-ph

Arjun Krishnan U M , Raul Puente , M.A.H.B. Md Yusoff , Herman Batelaan This is my paper · ORCID
classification quant-ph
keywords crosstalkcoincidencemeasurementantibunchingHanburyBrown-Twisseffectquantumdegeneracyelectronbeampulse-heightdistributiondiscriminatorthreshold
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

This paper argues that weak electromagnetic crosstalk between the start and stop channels of a coincidence detector can produce a false antibunching dip in the measured coincidence spectrum, independent of any electron-electron interaction. The authors demonstrate the effect with a heated tungsten wire source, where Coulomb repulsion and Pauli pressure are absent, observing an 8.5% dip at zero time delay. A model built from measured signal and crosstalk pulses predicts a 6.1% dip, and the paper notes that 1% crosstalk can lead to an 8% dip, which is large compared with the sub-0.1% quantum-degeneracy signals these experiments seek. The proposed remedy is to measure the same apparatus with a continuous random source and factor that normalized crosstalk dip out of the pulsed-source coincidence spectrum.

What carries the argument

The central object is the modified coincidence spectrum $C_{CT}(\tau) = M_c^A(\tau) M_c^B(\tau) C(\tau)$, where $C(\tau)$ is the cross-correlation of start and stop signal distributions in the absence of crosstalk, and $M_c^A(\tau)$, $M_c^B(\tau)$ are the fractional count losses of the two channels. Each loss factor is derived from the minimum of the sum of the real signal and the inverted crosstalk pulse, converted to a count loss through the measured pulse-height distributions and the discriminator threshold $V_{th}$. The mechanism is temporal overlap: at zero delay the negative signal and positive crosstalk align, lowering pulse heights, while at long delay they do not overlap. A linear extrapolation between full-overlap and no-overlap losses gives the delay-dependent correction used in the simulation.

What would settle it

Measure the zero-delay dip of a thermal electron source while deliberately varying only the proximity or shielding of the start and stop signal cables; the dip depth should track the independently measured crosstalk fraction and drop to zero when crosstalk is suppressed, if this mechanism is the cause.

Watch

Extended reading notes

Core claim

The central claim is that crosstalk does not need to create spurious coincidences to fake antibunching; it only needs to reduce the height of genuine coincidence pulses when a start and stop pulse overlap in time. The inverted crosstalk signal from one channel adds to the other channel's real signal, shifting the combined pulse below the discriminator threshold and removing counts at exactly the zero-delay peak. Measured crosstalk peaks of 1.2% and 1.3% of the signal peaks are sufficient to produce the observed 8.5% dip in a thermal-source spectrum with no interaction physics. The model, which combines the pulse-height distributions, the discriminator threshold, and the measured crosstalk waveform, reproduces the shape of the dip and predicts a 6.1% depth, explaining about 70% of the observed dip. The authors conclude that crosstalk can be identified and removed by using a continuous source as a reference, and they suspect that a previously reported 24% coincidence reduction attributed to Coulomb repulsion may have included a crosstalk component.

Load-bearing premise

The load-bearing premise is that the crosstalk signal measured in the separate oscilloscope calibration is the same as the crosstalk present during the actual coincidence run; if the real crosstalk is larger or shaped differently, the quantitative prediction changes.

Editorial extensions

If this is right

  • Any reported electron Hanbury Brown-Twiss antibunching dip should be accompanied by a crosstalk-calibrated measurement, because a 1% crosstalk can produce an 8% dip while quantum-degeneracy signals are expected below 0.1%.
  • A continuous-source run on the same apparatus provides a direct crosstalk fingerprint: if a dip appears there, it cannot be attributed to Coulomb or Pauli effects.
  • The normalized continuous-source dip can be factored out of pulsed-source data as a correction, removing the crosstalk contribution from the extracted correlation function.
  • Shielding signal cables reduces the effect, and raising the discriminator threshold is not a reliable cure because it also increases the absolute crosstalk voltage.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Beyond the paper's explicit claims, the same inverted-crosstalk mechanism should affect any two-channel time-correlated coincidence measurement with discriminators on a sloping pulse-height distribution, including optical Hanbury Brown-Twiss setups with avalanche detectors.
  • A testable extension would be to intentionally move the signal cables during a continuous-source measurement; the dip depth should change monotonically with measured crosstalk amplitude, confirming the causal link.
  • The proposed continuous-source correction assumes the pulse-height distribution and crosstalk amplitude are the same for pulsed and continuous operation; a direct check would be to compare the correction factor obtained in both modes on the same detector.
Share X Bluesky LinkedIn Reddit HN

Editorial analysis

A structured set of objections, weighed in public.

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

Circularity Check

0 steps flagged · score 1.0 of 10

No significant circularity: the crosstalk dip is predicted from independently measured crosstalk, pulse-height distributions, and threshold; the Eq. (7) printing issue is a consistency flaw, not a circular reduction.

full rationale

The crosstalk model is not circular. The input quantities are independently measured: the crosstalk amplitudes (1.2% and 1.3% of signal peak, Fig. 3), the time-averaged signal traces SA/SB and crosstalk traces CTA/CTB, the pulse-height distributions (Fig. 4), and the discriminator threshold Vth = 0.15 V. The loss fractions FA = 3.3% and FB = 2.4% are computed from those distributions via Eqs. (8)-(10), not fitted to the coincidence dip. Eqs. (5)-(7) then convert temporal overlap of signal and crosstalk into a fractional loss and multiply the crosstalk-free coincidence spectrum C(τ). The resulting 6.1% simulated dip is compared with the independently observed 8.5% dip rather than being matched to it, so the central claim is a genuine prediction. The continuous-source correction method is also a calibration subtraction, not a circular repackaging. The self-citations to Keramati et al. [1] and Batelaan et al. [8] are not load-bearing: Eq. (2) is the standard Poisson coincidence formula and the conclusion that part of the 24% reduction in [1] may be crosstalk is a reinterpretation of prior data, not evidence for the present model. A separate consistency caveat, not a circularity, is that Eq. (7) as printed appears to underpredict the reported simulation: with Ms(0)/Ms(∞) ≈ 1 - 0.012 and FA = 0.033, Eq. (7) gives M_c^A(0) ≈ 0.9996 rather than 1 - FA ≈ 0.967, suggesting a missing normalization or a slope/intercept misstatement. The paper's own limitation statement, that the 6.1% versus 8.5% discrepancy is attributed to 'the modified electronics while measuring the crosstalk with an oscilloscope in Fig.3,' is a calibration-representativeness concern, not a circular reduction. Overall, the derivation is self-contained against its measured inputs.

Assumptions & free parameters 1 free parameters · 6 assumptions · 0 invented entities

The model depends on measured crosstalk ratios, pulse height distributions, and several simplifying assumptions about pulse shapes and loss linearity. The only fitted parameter is the Gaussian width used to match peak widths. The central result is an experimental observation, with the model providing a partial explanation.

free parameters (1)
  • Gaussian temporal width sigma = 1.41 ns
    Chosen so that the simulated coincidence peak width matches the experimental FWHM of 4.73 ns (Section IV).
assumptions (6)
  • domain assumption The temporal distribution of start and stop pulses is Gaussian.
    Used in Eq. (4) and for the simulated peaks; not derived from first principles.
  • domain assumption The crosstalk signal has the same shape as the inverted signal pulse and scales linearly with signal amplitude.
    Supported by Fig. 3 measurements, but treated as a fixed proportionality (1.2% and 1.3% of signal).
  • domain assumption The fraction of lost counts varies linearly with the reduced pulse height (Eq. 7).
    The linear extrapolation between zero overlap and full overlap is stated as 'a reasonable assumption for the small amount of crosstalk' (Section IV).
  • domain assumption The thermal tungsten wire source produces a continuous random stream with no Coulomb or Pauli correlation between detected electrons.
    Key control assumption: used to attribute the thermal-source dip entirely to crosstalk (Section III).
  • standard math Poisson statistics describe the number of electrons emitted per laser pulse.
    Used in Eqs. (1)-(3) to describe the coincidence spectrum.
  • domain assumption The discriminator acts as a hard threshold on pulse height.
    The model in Eqs. (8)-(10) assumes counts are lost only when the reduced pulse height falls below Vth.

how reviews work

0 comments
Cite this review

Pith. "Pith review of Unusual crosstalk in coincidence measurement searches for quantum degeneracy." pith.science (2026). https://pith.science/paper/EQYBIGYG

@misc{pith2026241113863,
  author       = {Pith},
  title        = {Pith review of: Unusual crosstalk in coincidence measurement searches for quantum degeneracy},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/EQYBIGYG}},
  note         = {Machine review of arXiv:2411.13863}
}
read the original abstract

A dip in coincidence peaks for an electron beam is an experimental signature to detect Coulomb repulsion and Pauli pressure. This paper discusses another effect that can produce a similar signature but that does not originate from the properties of the physical system under scrutiny. Instead, the detectors and electronics used to measure those coincidences suffer significantly even from weak crosstalk. A simple model that explains our experimental observations is given. Furthermore we provide an experimental approach to correct for this type of crosstalk.

Figures

Figures reproduced from arXiv: 2411.13863 by the authors.

Figure 1
Figure 1. FIG. 1. Schematic set-up. Laser pulses (red) generate electron pulses from a nanotip, which are detected in coincidence by [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Fig.3. At [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figures from the paper (2 more)
Figure 3
Figure 3. Figure 3: FIG. 3. Background-subtracted time-averaged electron signal pulses from the CEMs and the resultant crosstalk on the start [PITH_FULL_IMAGE:figures/full_fig_p004_3.png]
Figure 4
Figure 4. Figure 4: FIG. 4. Pulse height distribution of the amplified electron [PITH_FULL_IMAGE:figures/full_fig_p004_4.png]

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

10 extracted references · 10 canonical work pages

  1. [1]

    Keramati, W

    S. Keramati, W. Brunner, T. J. Gay, and H. Batelaan, Non-poissonian ultrashort nanoscale electron pulses, Phys. Rev. Lett. 127, 180602 (2021)

    work page 2021

  2. [2]

    Haindl, A

    R. Haindl, A. Feist, T. Domr¨ ose, M. M¨ oller, J. H. Gaida, S. V. Yalunin, and C. Ropers, Coulomb-correlated elec- tron number states in a transmission electron microscope beam, Nature Physics 19, 1410 (2023)

    work page 2023

  3. [3]

    Meier, J

    S. Meier, J. Heimerl, and P. Hommelhoff, Few-electron correlations after ultrafast photoemission from nanomet- ric needle tips, Nature Physics 19, 1402 (2023)

    work page 2023

  4. [4]

    Borrelli, T

    S. Borrelli, T. C. H. de Raadt, S. B. van der Geer, P. H. A. Mutsaers, K. A. H. van Leeuwen, and O. J. Luiten, Di- rect observation of sub-poissonian temporal statistics in a continuous free-electron beam with subpicosecond res- olution, Phys. Rev. Lett. 132, 115001 (2024)

    work page 2024

  5. [5]

    R. H. Brown and R. Twiss, Lxxiv. a new type of inter- ferometer for use in radio astronomy, The London, Edin- burgh, and Dublin Philosophical Magazine and Journal of Science 45, 663 (1954)

    work page 1954

  6. [6]

    Kiesel, A

    H. Kiesel, A. Renz, and F. Hasselbach, Observation of hanbury brown–twiss anticorrelations for free electrons, Nature 418, 392 (2002)

    work page 2002

  7. [7]

    Kuwahara, Y

    M. Kuwahara, Y. Yoshida, W. Nagata, K. Nakakura, M. Furui, T. Ishida, K. Saitoh, T. Ujihara, and N. Tanaka, Intensity interference in a coherent spin- polarized electron beam, Phys. Rev. Lett. 126, 125501 (2021). 6

    work page 2021

  8. [8]

    intensity interference in a coherent spin-polarized elec- tron beam

    H. Batelaan, S. Keramati, and T. J. Gay, Comment on “intensity interference in a coherent spin-polarized elec- tron beam”, Phys. Rev. Lett. 127, 229601 (2021)

    work page 2021

Show all 10 references
  1. [9]

    Kodama, N

    T. Kodama, N. Osakabe, and A. Tonomura, Correlation in a coherent electron beam, Phys. Rev. A 83, 063616 (2011)

    2011

  2. [10]

    Classen, R

    A. Classen, R. Corrˆ ea, F. Fleischmann, S. Semmler, M.-O. Pleinert, P. Hommelhoff, and J. von Zanthier, Hanbury brown and twiss interference of electrons in free space from independent needle tip sources (2024), arXiv:2401.17088 [quant-ph]

    2024

Pith tools

Reviewed August 12, 2026 · model on record in the stance chip above.