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Is energy conserved when nobody looks?

by Stanisław Sołtan, Mateusz Frączak, Wolfgang Belzig, Adam Bednorz

This is not the latest submitted version.

Submission summary

Authors (as registered SciPost users): Adam Bednorz · Wolfgang Belzig
Submission information
Preprint Link:  (pdf)
Date submitted: 2019-09-25 02:00
Submitted by: Bednorz, Adam
Submitted to: SciPost Physics
Ontological classification
Academic field: Physics
  • Quantum Physics
Approach: Theoretical


Conservation principles are essential to describe and quantify mechanical processes. Classically, the conservation holds objectively because the description of reality can be considered independent of observation. In quantum mechanics, however, invasive observations change quantities drastically, even those conserved classically. Interestingly, we find that the non-conservation is manifest even in weakly measured correlations if some of the observables do not commute with the conserved quantity. Our observation casts some doubt on the fundamental compatibility of conservation laws and quantum objectivity.

Current status:
Has been resubmitted

Reports on this Submission

Anonymous Report 1 on 2019-12-14 (Invited Report)


1- Timely topic
2- Nicely written
3- Proper references and positioning
4- Scientifically valid


1- Dangerous (oversold) conclusions


This is an interesting paper that is reminiscent of recent developments of quantum foundations (contextual objectivity) and quantum thermodynamics (measurement driven engines)

However, I always find dangerous that sentences like "Our observation cast some doubt on the compatibility of conservation laws and quantum objectivity", since both are necessary conditions to practice physics.

In the case of energy, energy can indeed change while measuring an observable which does not commute with the Hamiltonian, but this does not violate the world's energy conservation since the measurement channel provides energy.
Actually, the authors summarize this quite well in their conclusion: Conservation laws are contextual.

Requested changes

1- Milden the last sentence of the abstract

  • validity: good
  • significance: ok
  • originality: high
  • clarity: ok
  • formatting: good
  • grammar: excellent

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