Comments about "Schrödinger's cat" in Wikipedia

This document contains comments about the article Schrödinger's cat in Wikipedia
In the last paragraph I explain my own opinion.

Contents

Reflection

Introduction

The article starts with the following sentence.
Schrödinger's cat is a thought experiment, sometimes described as a paradox, devised by Austrian physicist Erwin Schrödinger in 1935
IMO you can not really discus Schrödinger's cat as a thought experiment. You can only discus the setup of an actual experiment and the possible outcomes, but not a whole theory.
The scenario presents a cat that may be simultaneously both alive and dead, a state known as a quantum superposition, as a result of being linked to a random subatomic event that may or may not occur.
The half live of this subatomic event or radioactive decay can be established by performing 1000 experiments. As such is the outcome of the Schrodinger Cat experiment 100% defined: If you wait long enough the cat is dead even without looking inside the box.

1. Origin and motivation

The EPR article highlighted the bizarre nature of quantum superpositions, in which a quantum system such as an atom or photon can exist as a combination of multiple states corresponding to different possible outcomes.
First of all it is very important to describe the quantum system in great detail and what is meant with multiple states.
Any way there is a hugh difference between an atom (which consists of protons, electrons and neutrons i.e quarks) versus a photon (which can be polarized). Secondly the concept of superpositions should be explained.
The prevailing theory, called the Copenhagen interpretation, said that a quantum system remained in this superposition until it interacted with, or was observed by, the external world, at which time the superposition collapses into one or another of the possible definite states
You have to know the physical details of the process involved. To claim that a process is in superposition requires a clear definition of what is meant. Generally speaking it is important to know if the process has reached its final state. You can speak about a final state only for stable processes. It is like stopping a spinning wheel before its come to rest by itself.
According to Schrödinger, the Copenhagen interpretation implies that the cat remains both alive and dead until the state has been observed.
That has nothing to do with the physical state of the cat, which is either alive or dead.
Schrödinger did not wish to promote the idea of dead-and-alive cats as a serious possibility; on the contrary, he intended the example to illustrate the absurdity of the existing view of quantum mechanics.
If that is the opinion of Schrödinger, than he was right
However, since Schrödinger's time, other interpretations of the mathematics of quantum mechanics have been advanced by physicists, some of which regard the "alive and dead" cat superposition as quite real
Than they are wrong

2 Thought experiment

Schrödinger's famous thought experiment poses the question, "when does a quantum system stop existing as a superposition of states and become one or the other?"
You can not discuss such an isue as a thought experiment.
Our intuition says that no observer can be in a mixture of states—yet the cat, it seems from the thought experiment, can be such a mixture.
The whole problem has nothing to do with our intuition. Neither an observer, nor a cat, nor any process can be in a mixture of two states, which are each other complement: 0 or 1
What is feasible is that the true state is not known.
Is the cat required to be an observer, or does its existence in a single well-defined classical state require another external observer?
Again observers have nothing to do with this.

3. Interpretations of the experiment

Since Schrödinger's time, other interpretations of quantum mechanics have been proposed that give different answers to the questions posed by Schrödinger's cat of how long superpositions last and when (or whether) they collapse.
It is strange that these concepts are discussed with a thought experiment.
Concepts like "how long superpositions last" can only be decided based on actual experiments.
First of all you need a good physical definition.

3.1 Copenhagen interpretation

A commonly held interpretation of quantum mechanics is the Copenhagen interpretation.In the Copenhagen interpretation, a system stops being a superposition of states and becomes either one or the other when an observation takes place.
The physical state of any physical process has nothing to do if we humans look at it Yes or no. See also: Reflection 1 - Quantum Mechanics
This thought experiment makes apparent the fact that the nature of measurement, or observation, is not well-defined in this interpretation.
What is not well defined is what is meant that a physical process can be in two states simultaneous.
Niels Bohr, never had in mind the observer-induced collapse of the wave function, so that Schrödinger's cat did not pose any riddle to him.
Than what was the problem accordingly to Niels Bohr?
The cat would be either dead or alive long before the box is opened by a conscious observer.
That is 100% corect.
Analysis of an actual experiment found that measurement alone (for example by a Geiger counter) is sufficient to collapse a quantum wave function before there is any conscious observation of the measurement, although the validity of their design is disputed.
The "collapse of a quantum wave function" has nothing to do with this experiment, nor with any physical experiment.
"Observation" of the outcome has also nothing to do with this.
The thought experiment requires an "unconscious observation" by the detector in order for waveform collapse to occur. In contrast, the many worlds approach denies that collapse ever occurs.
Only the last part of the second sentence makes any sense.

3.2 Many-worlds interpretation and consistent histories

In the many-worlds interpretation, both alive and dead states of the cat persist after the box is opened, but are decoherent from each other.
If you want to understand something then that 'something' should be clear. What means decoherent?
when the box is opened, the observer and the possibly-dead cat split into an observer looking at a box with a dead cat, and an observer looking at a box with a live cat.
Nonsense Observing a process has nothing to do with the physical evolution of a process.
However, the mainstream view (without necessarily endorsing many-worlds) is that decoherence is the mechanism that forbids such simultaneous perception.
The mainstream view should be that observing any process has no influence on the outcome.

3.3 Ensemble interpretation

The ensemble interpretation states that superpositions are nothing but subensembles of a larger statistical ensemble
If you want to understand something then that 'something' should be clear.
I do not understand any part of this 'discussion'.

3.4 Relational interpretation

The relational interpretation makes no fundamental distinction between the human experimenter, the cat, or the apparatus, or between animate and inanimate systems; all are quantum systems governed by the same rules of wavefunction evolution, and all may be considered "observers".
Specific wavefunctions have nothing to do with this.

3.5 Transactional interpretation

In the transactional interpretation the apparatus emits an advanced wave backward in time, which combined with the wave that the source emits forward in time, forms a standing wave.
Waves have nothing to do with the evolution of physical processes

3.6 Zeno Effects

For example, if you peek a look into the cat box frequently you may either cause delays to the fateful choice or, conversely, accelerate it.
In principle an operator can influence the outcome of an experiment. However just by looking, with your hands behind your back, should not cause any influence. Otherwise you are cheating.

3.7 Objective collapse theories

4. Applications and tests

5. Extensions

The issue here is, does the wave function "collapse" when the first observer looks at the experiment, or only when the second observer is informed of the first observer's observations?
There is no issue of wave function "collapse"

6. See also

Following is a list with "Comments in Wikipedia" about related subjects

Reflection 1 - Quantum Mechanics

The problem with the Schrödinger's Cat experiment is that we humans have nothing to do with the outcome of the experiment, which is in essence the outcome of a radio active process i.e. if the element has decayed Yes or No.
The outcome is either Yes or No. It can not be both. We humans have nothing to do with this. Observing the outcome has also no influence. To claim that the cat, before you look, is in both states simultaneous, is of no physical significance.

You cannot compare playing with a slot machine with the Schrödingers cat experiment because the two have one important difference. When you stop the slot machine, specific at that moment the final state (result) of the machine is decided. When you stop the slot machine later you get a different result.
When the half life time of the radio active element is 1 second and you look after 1 minute you know that the cat is dead. If you look after 1 hour the result is the same. If you look after 1 second you have a 50% chance that the cat is alive or dead, but never in both states.

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Created: 28 July 2017
Updated: 26 Ocober 2017

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