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arxiv: 1907.09836 · v1 · pith:KVF22BV7new · submitted 2019-07-23 · 🪐 quant-ph

Wave-particle duality revisited: Neither wave nor particle

Jan Sperling , Syamsundar De , Thomas Nitsche , Johannes Tiedau , Sonja Barkhofen , Benjamin Brecht , Christine Silberhorn This is my paper

Pith reviewed 2026-05-24 17:31 UTC · model grok-4.3

classification 🪐 quant-ph
keywords wave-particle dualityquantum opticssqueezed lightnonclassicalityquantum coherenceinterferometercorrelation criteriaphoton statistics
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The pith

Neither wave nor particle models suffice to predict quantum-optical experiment outcomes.

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

The paper demonstrates that in an interferometer fed with squeezed light, measured correlations violate the conditions required by any wave-only description and any particle-only description. Criteria are first derived that must hold if the input is purely waves or purely particles. Experimental data from squeezed light then fails both sets of criteria inside the same setup. This directly challenges the textbook view that quantum objects can always be captured by one picture or the other depending on the measurement. The result is also tied to two incompatible notions of quantum coherence as an information resource, allowing certification of nonclassicality for coherent states when viewed in the particle picture.

Core claim

Neither the wave nor the particle description is sufficient to predict the outcomes of quantum-optical experiments. Correlation-based criteria are derived that have to be satisfied when either particles or waves are fed into the interferometer. Using squeezed light, measured correlations are incompatible with either picture. Thus, within one single experiment, neither a wave nor a particle model explains the observed phenomena. A relation is formulated of wave and particle representations to two incompatible notions of quantum coherence, certifying the nonclassicality of coherent states in the particle picture.

What carries the argument

Correlation-based criteria that any wave-only or particle-only model must obey in the interferometer, tested for violation with squeezed light.

If this is right

  • A single experiment can rule out both wave and particle models simultaneously.
  • Coherent states can be certified as nonclassical when analyzed in the particle picture.
  • Wave and particle representations correspond to incompatible notions of quantum coherence.
  • An information-theoretic view of the method links the result to quantum information resources.

Where Pith is reading between the lines

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

  • The result suggests that quantum optics may require descriptions that combine or transcend the two classical pictures rather than switching between them.
  • Similar correlation tests could be applied to other interferometric setups to check whether duality fails more generally.
  • The link to coherence as a resource might allow new certification protocols that switch the chosen picture depending on the task.

Load-bearing premise

The derived correlation criteria are assumed to be exhaustive and necessary for every possible wave-only or particle-only model in the interferometer.

What would settle it

Observing correlations in the squeezed-light interferometer that satisfy the criteria for either the wave picture or the particle picture would falsify the incompatibility claim.

Figures

Figures reproduced from arXiv: 1907.09836 by Benjamin Brecht, Christine Silberhorn, Jan Sperling, Johannes Tiedau, Sonja Barkhofen, Syamsundar De, Thomas Nitsche.

Figure 1
Figure 1. Figure 1: FIG. 1. (a) Two waves interfere constructively (top) and destruc [PITH_FULL_IMAGE:figures/full_fig_p001_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Theory benchmark for the lossless case. (a) Coherent states [PITH_FULL_IMAGE:figures/full_fig_p002_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Experimentally verified wave-particle violation (nonclas [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. For coherent states, our results (including uncertainties, one [PITH_FULL_IMAGE:figures/full_fig_p006_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Schematic of the setup. Ti:Sa: titanium sapphire laser; P [PITH_FULL_IMAGE:figures/full_fig_p008_5.png] view at source ↗
read the original abstract

A textbook interpretation of quantum physics is that quantum objects can be described in a particle or a wave picture, depending on the operations and measurements performed. Beyond this widely held believe, we demonstrate in this contribution that neither the wave nor the particle description is sufficient to predict the outcomes of quantum-optical experiments. To show this, we derive correlation-based criteria that have to be satisfied when either particles or waves are fed into our interferometer. Using squeezed light, it is then confirmed that measured correlations are incompatible with either picture. Thus, within one single experiment, it is proven that neither a wave nor a particle model explains the observed phenomena. Moreover, we formulate a relation of wave and particle representations to two incompatible notions of quantum coherence, a recently discovered resource for quantum information processing.For such an information-theoretic interpretation of our method, we certify the nonclassicality of coherent states - the quantum counterpart to classical waves - in the particle picture, complementing the known fact that photon states are nonclassical in the typically applied wave picture.

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

2 major / 1 minor

Summary. The manuscript claims that neither the wave nor the particle picture suffices to predict outcomes in quantum-optical experiments. It derives correlation-based criteria that must be satisfied for particle or wave inputs to an interferometer, then shows that squeezed-light measurements violate both sets of criteria. The work further relates the two pictures to incompatible notions of quantum coherence and uses the particle picture to certify nonclassicality of coherent states.

Significance. If the derived criteria are necessary and exhaustive for all wave-only and particle-only models, the result would challenge the textbook wave-particle duality interpretation and supply an information-theoretic route to certifying nonclassicality that complements existing wave-picture tests. The experimental demonstration with squeezed light would then constitute a concrete falsification within a single setup.

major comments (2)
  1. [Abstract and theory section] Abstract and theory section: The central claim that measured correlations are 'incompatible with either picture' requires that the derived criteria are necessary conditions for *any* wave-only or particle-only model. No explicit proof or argument is supplied that the criteria exhaust all possible models (e.g., wave models with additional phase/amplitude degrees of freedom or particle models with non-Poissonian or correlated emission statistics). Without this, the incompatibility conclusion does not follow.
  2. [Experimental section] Experimental section: The squeezed-light data are shown to violate the stated criteria, but the manuscript does not demonstrate that the observed correlations cannot be reproduced by some generalized wave or particle model that still satisfies the definitional requirements of those pictures. This gap directly affects the load-bearing claim that 'neither a wave nor a particle model explains the observed phenomena.'
minor comments (1)
  1. Notation for the correlation functions should be defined once at first use and used consistently thereafter.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and constructive feedback. Below we respond point-by-point to the major comments, clarifying the logical status of the derived criteria.

read point-by-point responses

  1. Referee: [Abstract and theory section] Abstract and theory section: The central claim that measured correlations are 'incompatible with either picture' requires that the derived criteria are necessary conditions for *any* wave-only or particle-only model. No explicit proof or argument is supplied that the criteria exhaust all possible models (e.g., wave models with additional phase/amplitude degrees of freedom or particle models with non-Poissonian or correlated emission statistics). Without this, the incompatibility conclusion does not follow.

    Authors: The theory section derives the criteria as necessary consequences of the definitional assumptions of each picture. For the particle picture the assumptions are independent emission events obeying Poissonian statistics; the correlation bounds then follow directly from the resulting multinomial probabilities. For the wave picture the assumptions are classical field amplitudes whose intensities add linearly; the bounds follow from the non-negativity of intensities and the Cauchy-Schwarz inequality applied to the measured second-order correlations. Any model that remains inside these definitional constraints—regardless of extra phase or amplitude parameters—must still obey the same inequalities, because the derivations rely only on those core statistical properties. Models that introduce non-Poissonian or correlated particle emission, or that allow negative intensities, cease to be particle-only or wave-only models under the definitions employed in the manuscript. revision: no

  2. Referee: [Experimental section] Experimental section: The squeezed-light data are shown to violate the stated criteria, but the manuscript does not demonstrate that the observed correlations cannot be reproduced by some generalized wave or particle model that still satisfies the definitional requirements of those pictures. This gap directly affects the load-bearing claim that 'neither a wave nor a particle model explains the observed phenomena.'

    Authors: Because the criteria are necessary under the definitional requirements, any model—generalized or otherwise—that satisfies those requirements is forbidden from producing correlations outside the derived bounds. The experimental violation therefore excludes every model that remains within the wave or particle definitions. The manuscript does not claim to rule out models that abandon the definitional requirements; it claims only that no model obeying those requirements can account for the data. revision: no

Circularity Check

0 steps flagged

No circularity; criteria derived independently then tested

full rationale

The paper first derives correlation criteria that must hold under explicit wave-amplitude or particle-number assumptions for the interferometer, then reports that squeezed-light data violate both sets of inequalities. No equation reduces a claimed prediction to a fitted input by construction, no load-bearing premise rests on a self-citation chain, and the central incompatibility statement is not obtained by renaming or ansatz smuggling. The derivation therefore remains self-contained against the stated assumptions.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the assumption that the (undetailed) correlation criteria fully capture wave and particle behavior; the abstract provides no free parameters, invented entities, or additional axioms beyond standard quantum optics.

axioms (1)
  • domain assumption Standard assumptions of quantum optics and linear interferometry hold for the setup.
    Invoked implicitly when deriving criteria that any wave or particle input must satisfy.

pith-pipeline@v0.9.0 · 5720 in / 1307 out tokens · 49835 ms · 2026-05-24T17:31:46.509138+00:00 · methodology

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Reference graph

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