Regarding this experiment which was carried out in 2012:


I'm wondering how could the scientific society be totally convinced(prior to this paper being published) based on a purely theoretical ground that the Observer Effect is not the true content of Kennard's derivation of Heisenberg's uncertainty principle, notwithstanding that his derivation doesn't resort to interactive measurement( measurement with light being shed on a system or whatever you like).

Since one could still stick to a view on QM which considers the theory as the theory of measurement and not an intrinsic and interaction-free general theory so that even Kennard's derivation can be considered as merely a semantical flourishing of the "observer effect" rather than a theoretically vital refusal of the "observer effect".

I mean one could still take the position that QM is intrinsically inclusive of interactive measurements that are carried out to exploit information about a system, no matter if the language and semantics seemed to be ignorant/independent of any interaction. A view that considers QM as an effective theory of measurement that has interaction implicit in itself.

I guess it's not bad to share the abstract of the paper itself which doesn't leave space for ambiguity:

While there is a rigorously proven relationship about uncertainties intrinsic to any quantum system, often referred to as “Heisenberg’s Uncertainty Principle,” Heisenberg originally formulated his ideas in terms of a relationship between the precision of a measurement and the disturbance it must create. Although this latter relationship is not rigorously proven, it is commonly believed (and taught) as an aspect of the broader uncertainty principle. Here, we experimentally observe a violation of Heisenberg’s “measurement-disturbance relationship”, using weak measurements to characterize a quantum system before and after it interacts with a measurement apparatus. Our experiment implements a 2010 proposal of Lund and Wiseman to confirm a revised measurement disturbance relationship derived by Ozawa in 2003. Its results have broad implications for the foundations of quantum mechanics and for practical issues in quantum mechanics.

  • $\begingroup$ Related: physics.stackexchange.com/q/24068/50583 and its linked questions $\endgroup$
    – ACuriousMind
    Commented Jan 11, 2021 at 16:19
  • $\begingroup$ Also, without clicking on the link you provided, it is completely unclear what "influential experiment" you are talking about. Please consider including a summary of the content in the question itself. $\endgroup$
    – ACuriousMind
    Commented Jan 11, 2021 at 16:20
  • $\begingroup$ @ACuriousMind In none of the answers to similar questions, no one has alluded to any theoretical or even experimental reason behind why one shouldn't take into account QM as a flourished and only seemingly observation independent theory of nature that takes into account observer effect implicitly. Everybody is satisfied with the semantical circumvention of the problem which was already done by Kennard for the first time. I'd be happy if one could go beyond this rather linguistic justification and convince us that the observer effect HUP leads to falsifiable contradictions. Perhaps via EPR. $\endgroup$ Commented Jan 11, 2021 at 19:22

1 Answer 1


The easiest theoretical way to see that the uncertainly principle can't be explained by interaction with the measurement apparatus is just to note that the uncertainly principle applies even when there is no interaction with the measurement apparatus.

For example, if you put a thin cloud chamber in the path of a wide coherent particle beam, you'll see short particle tracks that are localized in position, and downstream from the cloud chamber the particles will have a wider distribution of transverse momenta, at least as wide as required by the uncertainty principle. If there's a small hole in the cloud chamber, then particles not detected by the cloud chamber (which therefore must have gone through the hole) will spread out transversely downstream from the cloud chamber in the same way as if they'd been detected by the cloud chamber at that location.

I think it would be very difficult to do an experiment of this sort in practice, and there would inevitably be loopholes, i.e., ad-hoc alternate explanations of the result. But in a thought-experiment, you can close loopholes by fiat and assume quantum mechanics to be true, and the prediction of quantum mechanics is unambiguously that the uncertainty principle applies when there isn't an interaction just as when there is.

  • $\begingroup$ Isn't the HUP connected with the theory of quantum mechanics at the basic level of commutators?quantummechanics.ucsd.edu/ph130a/130_notes/node188.html $\endgroup$
    – anna v
    Commented Jan 12, 2021 at 6:10
  • $\begingroup$ I'm curious about your view on Balentine's argument to reject Bohm's interpretation of UP, as well as Heisenberg-Bohr's. Here on page 365, there's a couple of thought experiments provided to reject both views: The Statistical Interpretation of Quantum Mechanics L. E. BALLENTINE Rev. Mod. Phys. 42, 358 – Published 1 October 1970 link $\endgroup$ Commented Jan 12, 2021 at 12:26
  • $\begingroup$ At all. What you're referring to is a merely mathematical formalism which is absolutely insufficient and doesn't clarify the meaning of UP. As an example consider Heisenberg-Bohr who multiple times gave an account of UP as an observer effect while Bohm's view on UP is the modern one that you're referring to. But Balentine criticizes both former views based on gedankenexperiments. @annav $\endgroup$ Commented Jan 12, 2021 at 12:34
  • $\begingroup$ And one should keep in mind that it's not merely a matter of interpretation as the EPR paradox and Bell's inequalities are quite contributing to our understanding of the world. Especially that they are experimentally grounded. @annav $\endgroup$ Commented Jan 12, 2021 at 12:34
  • $\begingroup$ @BastamTajik I was asking "benrg". For me, as an experimentalist , the fact that the quantum field theoretical model is very successful in fitting the grand majority data is enough of a proof that the commutators describe which variables can behave with an uncertainty relation and which with none. . imho all the rest is navel gazing. $\endgroup$
    – anna v
    Commented Jan 12, 2021 at 13:21

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