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arxiv: 2606.20396 · v1 · pith:TIFT37T7new · submitted 2026-06-18 · 🪐 quant-ph

Faking entanglement with imperceptible measurement deviations

Jaime Moreno , Elna Svegborn , Simon Morelli , Markus Hiekkam\"aaki , Lea Kopf , Robert Fickler , Armin Tavakoli This is my paper

Pith reviewed 2026-06-26 17:00 UTC · model grok-4.3

classification 🪐 quant-ph
keywords quantum entanglementmeasurement errorshigh-dimensional entanglemententanglement witnessesphotonic statesseparabilityquantum hacking
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The pith

Arbitrarily small measurement errors can falsely certify high-dimensional entanglement in separable systems.

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

The paper establishes that by deliberately embedding tiny adversarial errors into the measurement apparatus, standard tests for high-dimensional entanglement can report a violation even when the physical state is fully separable. This is shown through explicit constructions of measurement hacks on entanglement witnesses, followed by an experiment that uses classical light in spatial modes to produce apparent entanglement up to 61 dimensions with fidelity errors of only 0.23 percent. A sympathetic reader would care because entanglement certification underpins many quantum technologies, so undetected measurement deviations could lead to incorrect claims about the presence of a key resource.

Core claim

Arbitrarily small measurement errors, when adversarially encoded in the measurement apparatus, can lead to the false certification of high-dimensional entanglement in systems that are, in fact, separable. This is achieved by introducing explicit hacking attacks to measurement devices in well-established entanglement verification tests and experimentally demonstrated using classical photonic states encoded in the spatial degree of freedom spanning up to 61 dimensions.

What carries the argument

Adversarially encoded measurement deviations applied to entanglement witness tests, which shift the observed statistics enough for separable states to exceed the separability bound.

Load-bearing premise

The photonic states remain strictly separable with the witness violation caused only by the introduced measurement deviation and no other hidden correlations or imperfections.

What would settle it

Repeating the spatial-mode experiment with the same introduced deviations but independently confirming that the measured statistics match the separable prediction exactly would show the claim does not hold.

read the original abstract

Quantum entanglement is a central resource underpinning emerging quantum technologies, enabling capabilities beyond those of classical systems. Accurate verification of entanglement is therefore crucial. However, experimental schemes usually rely on the assumption that quantum measurements can be realized exactly. As the complexity of a quantum system grows, this assumption typically becomes increasingly unrealistic, therefore leading to a widening mismatch between theoretical models and experimental implementations. Here we demonstrate that arbitrarily small measurement errors, when adversarially encoded in the measurement apparatus, can lead to the false certification of high-dimensional entanglement in systems that are, in fact, separable. This is achieved by introducing explicit hacking attacks to measurement devices in well-established entanglement verification tests. We further experimentally demonstrate this effect using classical photonic states encoded in the spatial degree of freedom, spanning up to 61 dimensions with measurement fidelity errors as low as 0.23%. Our results uncover a fundamental vulnerability in current methods for high-dimensional entanglement detection, highlighting the susceptibility of complex quantum devices to small adversarial perturbations. The findings underscore the need for developing secure verification of quantum information that is robust to bounded discrepancies between theory and experiment.

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 / 0 minor

Summary. The paper claims that arbitrarily small adversarial deviations in measurement devices can produce false positives for high-dimensional entanglement witnesses even when the underlying state is separable. It supports this with an explicit attack construction on standard verification protocols and an experimental demonstration using classical photonic states encoded in up to 61 spatial modes, achieving apparent entanglement certification with measurement fidelity errors as low as 0.23%.

Significance. If the central construction holds, the result identifies a concrete and previously under-appreciated vulnerability in high-dimensional entanglement certification that scales with system size. The explicit, parameter-free attack and the direct experimental mapping from classical separable states to apparent quantum correlations constitute a clear, falsifiable demonstration that strengthens the practical relevance of the claim.

major comments (2)
  1. [Experimental demonstration] The experimental section provides no independent separability witness or tomography performed with the original (unhacked) measurement operators on the 61-mode classical states. Without such a control, residual partial coherence, diffraction, or cross-talk could itself produce the observed witness violation, undermining the attribution of the effect solely to the 0.23% adversarial deviation.
  2. [Experimental demonstration] The manuscript supplies no error bars, repeated trials, or exclusion criteria for the classical-light data. This omission is load-bearing for the claim that the violation is produced exclusively by the introduced measurement hack rather than by uncontrolled experimental imperfections.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and constructive comments. Below we respond point-by-point to the major comments on the experimental demonstration.

read point-by-point responses

  1. Referee: The experimental section provides no independent separability witness or tomography performed with the original (unhacked) measurement operators on the 61-mode classical states. Without such a control, residual partial coherence, diffraction, or cross-talk could itself produce the observed witness violation, undermining the attribution of the effect solely to the 0.23% adversarial deviation.

    Authors: We agree that an explicit control with the original measurement operators would strengthen attribution. Although the states are classical photonic fields (provably separable by classical electromagnetism), we will add in revision the witness values obtained on the same 61-mode states using the unhacked operators, confirming no violation occurs. This control will be included as supplementary data or an additional panel. revision: yes

  2. Referee: The manuscript supplies no error bars, repeated trials, or exclusion criteria for the classical-light data. This omission is load-bearing for the claim that the violation is produced exclusively by the introduced measurement hack rather than by uncontrolled experimental imperfections.

    Authors: We accept this criticism. The revised manuscript will report error bars on all witness values, specify the number of repeated trials performed for each dimension, and detail the data exclusion criteria applied. These additions will be placed in the experimental methods and results sections. revision: yes

Circularity Check

0 steps flagged

No significant circularity; explicit attack construction and experimental demo are self-contained

full rationale

The paper constructs explicit adversarial measurement deviations and demonstrates their effect on witness violation using classical photonic states claimed to be separable. No equation or result is defined in terms of a fitted parameter that is then relabeled as a prediction, no self-citation chain bears the central claim, and no ansatz or uniqueness theorem is smuggled in. The derivation chain consists of direct construction plus laboratory realization rather than reduction to its own inputs.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the domain assumption that classical photonic states are separable and that the only deviation from ideal measurements is the adversarially chosen error; no free parameters are introduced beyond the reported experimental fidelity value.

axioms (1)
  • domain assumption Classical light in the spatial degree of freedom is separable and cannot exhibit quantum entanglement.
    Invoked to guarantee that any apparent entanglement signal must originate from the measurement deviation rather than the input state.

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discussion (0)

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Reference graph

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