Schrödinger's Cat, uncertainty, and observation question

In summary: The key issue has to do with the difference between improper and proper mixtures.There are ways to measure quantum phenomena using specialised equipment, but they are not as common as one might think.In summary, the descriptions of an observation or measurement in Quantum Mechanics have been quite vague. Since the word measurement is used alternatively, I am going to assume that this includes all types of measurements. This brings me to a question. If the box Schrödinger's cat was in was not lead lined (And we assume the source is not an Alpha emitter as the box would likely block it), would one be able to use a Geiger counter to detect if decay had occurred or would this take the cat out of superposition
  • #1
themadquark
22
1
First of all, from what I've read the descriptions of an observation or measurement in Quantum Mechanics have been quite vague. Since the word measurement is used alternatively I am going to assume that this includes all types of measurements, which brings me to a question. If the box Schrödinger's cat was in was not lead lined (And we assume the source is not an Alpha emitter as the box would likely block it) would one be able to use a Geiger counter to detect if decay had occurred or would this take the cat out of superposition, thus making it either dead or alive?
 
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  • #2
Yes. Any way of "looking inside the box" counts.
The idea of the thought-experiment is that the experimenter is able to choose when he looks.
 
  • #3
Simon is correct.

But please understand according to the standard Copenhagen interpretation QM is a theory about observations that appear in an assumed common sense classical world. In Schrodenger's Cat that observation occurs at the particle detector. Everything is common sense classical from that point on. The cat is alive or dead period. It makes no difference if its observed or not.

The purpose of Schroedinger's Cat was to illustrate a issue with Copenhagen. Since QM is a theory about observations in an assumed classical world and QM is the fundamental theory that is supposed to explain that world - well it obviously will find that a bit hard. It doesn't invalidate Copenhagen, but its a blemish. What is needed is a fully quantum theory of measurement.

A lot of progress has been made to that end:
http://www.ipod.org.uk/reality/reality_decoherence.asp

But without going into the details a few issues still remain eg the so called factoring problem.

Thanks
Bill
 
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  • #4
But yeah - a QM theory of measurement is kinda the physics form of the mind-body problem.
 
  • #5
I appreciate the excellent answers, but feel I must ask: What proposals are there for a specialised method of measuring quantum phenomena, if any?
 
  • #6
bhobba gave you a good link for how measurement may be modeled in QM.

In QM experiments we just use detectors and so on normally, using the theory to make predictions about the outcome. i.e. if we want to know if the cat is dead we open the box and look.
 
  • #7
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Related to Schrödinger's Cat, uncertainty, and observation question

1. What is Schrödinger's Cat thought experiment?

Schrödinger's Cat is a thought experiment proposed by physicist Erwin Schrödinger in 1935. It is a paradox that illustrates the principles of quantum mechanics and the concept of superposition. The experiment involves a cat in a sealed box with a device that has a 50% chance of releasing a poison, killing the cat. According to quantum mechanics, until the box is opened and observed, the cat is considered to be both alive and dead at the same time, in a state of superposition.

2. How does Schrödinger's Cat relate to the uncertainty principle?

Schrödinger's Cat thought experiment highlights the uncertainty principle, which is a fundamental principle of quantum mechanics. It states that it is impossible to know certain properties of a particle, such as its exact position and momentum, at the same time. In the experiment, the cat's state of being both alive and dead at the same time represents the uncertainty of the particle's state until it is observed.

3. What is the role of observation in Schrödinger's Cat experiment?

In Schrödinger's Cat experiment, observation plays a crucial role. According to quantum mechanics, the act of observation or measurement causes the superposition to collapse into one definite state. In this case, opening the box and observing the cat causes it to be either alive or dead, not both. This concept is known as the observer effect.

4. Is Schrödinger's Cat experiment meant to be taken literally?

No, Schrödinger's Cat experiment is a thought experiment that was designed to highlight the principles of quantum mechanics, rather than being a real experiment. It was proposed by Schrödinger to show the absurdity of applying quantum mechanics to macroscopic objects, such as a cat. It is not meant to be taken literally, but rather as a way to understand the concepts of superposition and uncertainty.

5. What is the significance of Schrödinger's Cat experiment in science?

Schrödinger's Cat experiment has significant implications in the field of science, particularly in quantum mechanics. It challenges our understanding of reality and the role of observation in determining it. The experiment has sparked many debates and discussions among scientists and philosophers, and it continues to be a crucial thought experiment in understanding the principles of quantum mechanics.

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