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arxiv: 2606.27817 · v1 · pith:62DFJOOJnew · submitted 2026-06-26 · 🪐 quant-ph · physics.optics

Detector-Conditioned Source-Space Nulls and Null-Mask Loss in a Programmable Two-Slit Interferometer

Jianming Wen This is my paper

Pith reviewed 2026-06-29 04:51 UTC · model grok-4.3

classification 🪐 quant-ph physics.optics
keywords Afshar experimentdouble-slit interferometerwave-particle complementaritysource-space nullsdetector-conditioned responseFresnel modelwhich-path information
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The pith

In a time-reversed Afshar setup, source-space nulls obey standard complementarity via detector-conditioned response.

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

The paper proposes moving the null test of Afshar's experiment from the field plane to the source plane in a programmable two-slit interferometer. A scanned point source illuminates the slits while a fixed detector records the response, creating a reconstructed pattern where nulls indicate source positions with vanishing transfer amplitude to the detector. Masks at these nulls are invisible to the detector when both slits are open but visible with one slit alone. The visibility and path distinguishability still satisfy the usual duality relation, showing that the effect is a reciprocal form of complementarity rather than a violation.

Core claim

A point-addressable source scanned in a double-slit interferometer produces a detector-conditioned response pattern rather than a spatial intensity fringe. Source-space nulls occur where the coherent two-slit amplitude to the selected detector vanishes. A mask placed at such a null is transparent to that detector with both slits open, yet blocks transmission when either slit acts alone. The source-space visibility and path distinguishability satisfy V^2 + D^2 = 1, so complementarity holds. The new feature is detector-conditioned response-function transparency in the reconstructed source basis.

What carries the argument

Detector-conditioned source-space null condition derived from the scalar Fresnel model, which identifies source labels where the transfer amplitude to a fixed detector cancels and defines the associated null-mask loss.

If this is right

  • Source-space visibility and path distinguishability satisfy the standard duality relation.
  • No violation of complementarity is implied by the reciprocal geometry.
  • The null-mask loss evolves under a tunable which-path marker.
  • The configuration allows a programmable test of detector-conditioned transparency.

Where Pith is reading between the lines

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

  • This reciprocal setup could be implemented with programmable spatial light modulators to scan sources without physical movement.
  • The idea extends naturally to multi-slit or more complex interferometers where response functions can be conditioned on detector choice.
  • It raises the question of whether similar conditioned nulls appear in quantum versions with entangled sources.

Load-bearing premise

The scalar Fresnel model captures the essential propagation physics and remains valid for point-by-point source scanning while coherence between slits is preserved.

What would settle it

Measure the detector response while scanning a coherent point source across the input plane of a double-slit setup and check whether null positions match the predicted source labels where the two-slit amplitude sums to zero, with the mask effect appearing only for the combined paths.

Figures

Figures reproduced from arXiv: 2606.27817 by Jianming Wen.

Figure 1
Figure 1. Figure 1: FIG. 1. Conceptual distinction between conventional Afshar [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Input–output response map of the normalized two [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Source-space nulls and detector-conditioned null [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Complementarity through source-space null filling. [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Shifted-mask diagnostic of a source-space null. The [PITH_FULL_IMAGE:figures/full_fig_p008_5.png] view at source ↗
read the original abstract

Afshar's double-slit experiment probes wave--particle complementarity by placing a wire grid at the dark fringes of a downstream interference pattern while retaining an imaging basis that appears to preserve which-path information. Here we propose and analyze a time-reversed Young--Afshar configuration in which the corresponding null test is transferred from the downstream field plane to the source-label plane of a time-reversed Young interferometer. In this reciprocal geometry, a point-addressable source illuminates a double slit, while the detector remains fixed. The observed fringe is therefore not a single-shot spatial intensity pattern, but a detector-conditioned response reconstructed by scanning the source coordinate. Consequently, a null in this pattern is not a node of a freely propagating field; it is a source label for which the coherent two-slit transfer amplitude to the selected detector vanishes. A mask placed at such source-plane labels is invisible to that detector when both slits are open, yet becomes visible when either slit is opened alone. We develop the scalar Fresnel model, derive the source-space null condition, introduce a detector-conditioned null-mask loss, and examine how this loss evolves under a tunable which-path marker. The source-space visibility and path distinguishability satisfy the standard duality relation, so no violation of complementarity is implied. The essential new feature is instead a reciprocal, detector-conditioned form of complementarity: Afshar's field-space transparency is replaced by response-function transparency in a reconstructed source basis.

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

1 major / 0 minor

Summary. The manuscript analyzes a time-reversed Young-Afshar interferometer in which a point-addressable source scans the input while a detector is held fixed. Using a scalar Fresnel propagator, the authors derive conditions under which the coherent two-slit transfer amplitude to the selected detector vanishes, yielding nulls in the reconstructed source-space response. They introduce a detector-conditioned null-mask loss and track its evolution under a tunable which-path marker. The source-space visibility and path distinguishability obey the standard duality relation; the claimed novelty is a reciprocal, detector-conditioned form of complementarity in which source-label transparency replaces Afshar's field-space transparency.

Significance. If the Fresnel derivation is robust, the work supplies a reciprocal perspective on complementarity that is directly relevant to programmable interferometers and detector-conditioned measurements. The parameter-free construction of the null condition from the Fresnel transfer amplitude and the explicit tracking of the null-mask loss under the which-path marker are strengths that make the central claim falsifiable in principle.

major comments (1)
  1. [Derivation of the source-space null condition] The derivation of the source-space null condition (the vanishing of the coherent two-slit transfer amplitude) rests on the scalar Fresnel propagator remaining accurate when the source coordinate is scanned point-by-point while inter-slit coherence is preserved. The manuscript does not examine whether wavefront-curvature changes, coherence-length variations, or polarization mixing under this scanning protocol shift or destroy the predicted null locations; without such justification the claimed source-label transparency and the evolution of the null-mask loss cannot be taken as established.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their constructive assessment and for highlighting the need to justify the scalar Fresnel model under source scanning. We address the single major comment below and have incorporated a clarifying discussion in the revised manuscript.

read point-by-point responses

  1. Referee: The derivation of the source-space null condition (the vanishing of the coherent two-slit transfer amplitude) rests on the scalar Fresnel propagator remaining accurate when the source coordinate is scanned point-by-point while inter-slit coherence is preserved. The manuscript does not examine whether wavefront-curvature changes, coherence-length variations, or polarization mixing under this scanning protocol shift or destroy the predicted null locations; without such justification the claimed source-label transparency and the evolution of the null-mask loss cannot be taken as established.

    Authors: We agree that an explicit statement on the regime of validity is warranted. Within the scalar monochromatic Fresnel framework adopted throughout the manuscript, the source scan is performed at fixed propagation distance and wavelength, with inter-slit coherence imposed by construction; the paraxial condition ensures that first-order wavefront-curvature corrections remain negligible for the displacements considered. Coherence-length variations and polarization mixing lie outside the scalar model and are not included. In the revision we have added a dedicated paragraph in Section II that states these assumptions and notes that a vector treatment would be required to assess polarization effects. The source-space null condition and null-mask loss therefore remain rigorously defined inside the stated model; the duality relation is unaffected. revision: partial

Circularity Check

0 steps flagged

No significant circularity; derivation self-contained under Fresnel model

full rationale

The paper develops the scalar Fresnel model and derives the source-space null condition from the coherent two-slit transfer amplitude to a fixed detector. The source-space visibility and path distinguishability are stated to satisfy the standard duality relation from prior literature, without redefinition inside the paper's equations. The detector-conditioned null-mask loss is constructed directly from the Fresnel transfer amplitude. No load-bearing step reduces by construction to a fitted parameter, self-citation chain, or ansatz smuggled via citation; the central claim remains independent of its inputs once the Fresnel propagator is assumed.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the scalar Fresnel propagation model and the assumption that a point-addressable source can be scanned while maintaining two-slit coherence; no free parameters or invented entities are mentioned in the abstract.

axioms (1)
  • domain assumption Scalar Fresnel diffraction integral accurately describes the coherent transfer amplitude from source coordinate through the two slits to the fixed detector.
    Invoked when the source-space null condition is derived from the model.

pith-pipeline@v0.9.1-grok · 5787 in / 1382 out tokens · 36992 ms · 2026-06-29T04:51:16.258853+00:00 · methodology

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Reference graph

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