Regarding the observer effect.

[vegetto34]

I got a question. Is this excerpt from wikipedia correct?

http://en.wikipedia.org/wiki/Observer_effect_(physics )

A common layman misuse of the term refers to quantum mechanics, where, if the outcome of an event has not been observed, it exists in a state of 'superposition', which is akin to being in all possible states at once. In the famous thought experiment known as Schrödinger's cat the cat is supposedly neither alive nor dead until observed. However, most quantum physicists, in resolving Schrödinger's seeming paradox, now understand that the acts of 'observation' and 'measurement' must also be defined in quantum terms before the question makes sense. From this point of view, there is no 'observer effect', only one vastly entangled quantum system.

Does that mean there is no observer effect when acts of observation and measurement are defined in quantum terms?

Does anyone have sources that augment or dispute this excerpt?

Thanks.

 

[Fredrik]

A measurement is an interaction between the system and its environment (which includes the measurement device), so the state of the system can obviously be changed by the measurement.

So this "observer effect" (as defined by the article) is clearly present in QM, but no one uses that term. I don't remember seeing it in any of the QM books I've read.

It's true that the measurement device obeys the rules of QM, but in realistic situations, the interactions between the device and its environment will ensure that the "pointer" (the component that indicates the result of the measurement) behaves in a way that's indistinguishable from classical behavior. In fact, if it behaved in any other way, we wouldn't consider it a measurement.

 

[vegetto34]

I see. So the excerpt isn't necessarily wrong? In other words, is it open to interpretation.

 

[D H]

I see. So the excerpt isn't necessarily wrong? In other words, is it open to interpretation.

The excerpt is not particularly well written and puts the emphasis on the wrong syLLAble. IMO, the paragraph on the uncertainty principle should have been first and foremost. The lay misinterpretation of the uncertainty principle is that it is the observer effect. This interpretation misses the mark in that the uncertainty principle talks about the uncertainty in a canonical pair of variables. http://en.wikipedia.org/wiki/Uncertainty_principle" says it much better (emphasis mine):

That is, the more precisely one property is known, the less precisely the other can be known. This is not a statement about the limitations of a researcher's ability to measure particular quantities of a system, it is a statement about the nature of the system itself as described by the equations of quantum mechanics.

 

[vegetto34]

Does that mean the term, the observer effect is used? I understand that the phenomena exists, but I haven't seen many academic sources using the term. However I've heard the term used in journals outside QM, though.

 

[f95toli]

No, it it not used at all as far as I know.
Although presumably you could across is it or something similar if you were reading academic paper that deals with the "philosophy" of QM and modern physics (and I don't mean interpretations but really philosophy), but that is not really physics (or science).

 

[kote]

No, it it not used at all as far as I know.
Although presumably you could across is it or something similar if you were reading academic paper that deals with the "philosophy" of QM and modern physics (and I don't mean interpretations but really philosophy), but that is not really physics (or science).

Interpretations are really philosophy. "Observer effect" isn't a technical philosophical term I've ever come across before though.

For examples of academic philosophy on QM see any of the papers on http://www.princeton.edu/~hhalvors/papers/.