Summary
Jiang et al. show that source attribution in a three-source quantum interferometer depends on how the coherent alternatives are grouped. We agree with this result and with their conclusion that which-source statements acquire meaning only after the relevant alternatives and experimental context are specified. We suggest, however, that one published phrase requires a narrower scope. The paper states that it is impossible to ascribe a definite physical origin to the detected photon pair even with full path information [1]. In their transparent peer-review response, the authors also clarify that the quantum formalism gives an objective description and that different interpretational narratives describe the same underlying quantum evolution [2]. Taken together, these statements support a precise conclusion: the experiment rules out a unique, partition-independent crystal-origin attribution within the tested path framework. A broader claim about physical origin requires an additional premise about what that path description is assumed to exhaust.
What the experiment establishes
The experiment contains three indistinguishable photon-pair generation processes whose probability amplitudes contribute coherently to the same detected modes [1]. The apparatus can be described through different binary groupings of these processes. For each grouping, strong which-source information can be obtained, yet the inferred source changes when the grouping changes. The important experimental result is therefore not that quantum mechanics gives an ambiguous prediction. The formalism and detected rates are well defined. What changes is the source narrative associated with the chosen decomposition of the coherent alternatives.
This is also the interpretation emphasized by Jiang et al. during peer review. They state that the purpose of the work is to analyse how which-path or which-source statements acquire meaning in concrete experimental contexts and how different groupings may be operationally justified [2]. They further agree that quantum mechanics remains an unambiguous predictive framework, while different interpretational narratives can describe the same underlying quantum evolution [2]. We regard this contextual result as both clear and important.
Where the remaining scope question arises
The published paper nevertheless uses stronger language, stating that a definite physical origin cannot be ascribed even when full path information is available [1]. The meaning of this statement depends on what ‘physical origin’ denotes. If it means a single crystal label that must remain valid under every legitimate partition of the tested which-source description, the experiment directly supports the claim. No such partition-independent label survives.
A broader reading is different. It would treat the failure of a unique crystal-origin attribution as evidence that the physical event itself admits no more definite account of origin than the tested path variable provides. That step requires an additional premise: that the which-source description used in the experiment exhausts the physically relevant meaning of origin. The experiment does not independently test that premise. In particular, ‘full path information’ is full information for the specified path question; it is not, by that fact alone, a demonstration that the chosen path variable is a complete description of physical reality.
A context-dependent source attribution does not by itself establish that no more definite physical account of origin exists.
Why the peer-review clarification matters
The transparent peer-review record makes this distinction narrower, not unnecessary. Jiang et al. explicitly reject the suggestion that quantum mechanics itself is subjective and instead locate the subjectivity in the interpretational story attached to an objective quantum evolution [2]. This clarification substantially limits the possible disagreement. It also identifies the safest reading of their result: the experiment demonstrates that different decompositions support different source attributions, not that the formal evolution becomes indeterminate or observer dependent.
Our point therefore does not require hidden variables, deterministic trajectories, or a competing interpretation of quantum mechanics. It concerns the level of conclusion warranted by the experiment. A contextual which-source variable may fail to supply a unique crystal label even if one remains agnostic about whether any richer physical description of origin exists. Conversely, proposing such a richer description would require separate assumptions and separate evidence; Jiang et al.’s experiment neither establishes nor excludes it.
A narrower statement of the result
We therefore suggest expressing the central result as follows: in this three-source coherent interferometer, no unique crystal-origin attribution can be made independently of how the relevant path alternatives are grouped. This formulation preserves the full experimental finding, the contextual character emphasized in the Discussion, and the authors’ peer-review clarification that the quantum evolution itself is objectively described.
If ‘definite physical origin’ in the published article is intended only in this operational sense, then our contribution is a clarification of scope. If the phrase is intended more broadly, then a further completeness argument is required to identify the experimentally defined which-source variable with an exhaustive account of physical origin. The present interference experiment alone does not provide that additional step.
Conclusion
Jiang et al. compellingly demonstrate that source attribution depends on the chosen decomposition of coherent alternatives. Their peer-review clarification further states that these differing narratives concern the same objectively described quantum evolution. We therefore distinguish contextual source attribution from a stronger claim about physical origin. The data establish that no partition-independent crystal-origin label is available within the tested which-source framework. Describing this as the impossibility of a definite physical origin is equivalent only if ‘physical origin’ is restricted to that operational variable, or if an additional completeness premise is supplied.
References
1. Jiang, X. et al. Subjective nature of path information in quantum mechanics. Nature Communications 17, 2433 (2026). doi:10.1038/s41467-026-69034-7.
2. Jiang, X. et al. Peer Review File for “Subjective nature of path information in quantum mechanics”. Nature Communications (2026), associated with doi:10.1038/s41467-026-69034-7.
3. Submitted to Nature Communications as a Matters Arising
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