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Each time I look video in regards to quantum physics there is almost always one point where they claim small matter can be represented by a wave function (can be everywhere but the item in question has an higher % of being at a specific location than far away) until it is observed (now seen as a particle).

In practice, what is considered as an "Observer"?

Is consciousness essential to the observer role?

Example1: Let's say X is not observed (so in the wave function state), then a device is placed to determine the location of X but the result is never looked at by a conscious being (assuming a human) .

Is X considered observed so now represented by a particle?

Example2: Same example as 1 but now a conscious being looks at the result of the device.

I assume X is now being considered observed therefore it is now represented as a particle.

Greg7000
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Is consciousness essential to the observer role?

No. What is usually meant by an 'observer' could be better described as 'something that interacts with the system.

Consider a particle (perhaps an electron) floating around in space, and let's call it X. X does not have a well defined position in space, instead it is described by a wavefunction. If it collides with a photon flying around you could still say X was 'observed by the photon', in that the photon interacted with the system of X. But photons don't have consciousness.

Jesse
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I would say that observer of a system A is any physical system B whose state remains unchanged through interaction with system A, or whose state always changes in the same way regardless of the state of system A. In other words it's a system that doesn't get any information about system A even when interacting with it.

If an interaction only changes the state of system A, but it doesn't change the state of system B, then system B is not an observer. Examples are: mirror reflecting a photon, a plate with two slits in Young experiment, alight-splitting plate. They definitely interact with our experimental system A, but does not change their own state. Thus they are not observers.

Systems that do change their state when interacting with system A are observers. The examples are: a particle detector, a soalr panel, a conscious person. All of them upon interaction change their state, and that change can be later further observed.

Of course no system truly remains unchanged in the interaction; so it can be argued that any real system interacting with system A is its observer. However, it can be noticed that sometimes system B observeres only some qualities of system A, and does not observe others. For example let's take the mirror reflecting a photon. It does not change it's state depending on the polarization of the reflected photon, so it does not observe the polarization of the photon; at the same time, it does change it's momentum accordingly to the momentum of the reflected photon, and thus it observes the momentum of the photon.

Adam Latosiński
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