Measurement/observation in QM

[E92M3]

What counts as a measurement in QM? I am having trouble with this concept and have the following questions:

1. Can I say that by looking at a certain experiment I've collapsed the wave function into a particular state? In that case, doesn't it mean that a blind person will get a different result for a given quantum experiment?
2. What is capable of making a measurement? Is a conscious mind required? What if, for instance, a computer takes and stores reading. In this case, does the wave function only collapses when the scientist retrieves the data from the computer?
3. A charge object will affect the E and B field around it. Doesn't this mean that it is constantly under observation? The same can be said with any object with mass. We can always "feel" the object from its gravity, so are those measurements?
4. After a measure, we know what state the system is in, and if we immediately take a measure of any compatible (commutable) observable, we can be sure what eigenvalue we would get. In this case, how long would the system stay in such a state? Will it be in the state forever as long as we don't that measurements of non-compatible observables?

 

[malawi_glenn]

question 2 object to current philosophy of science discussion. It depends also on what interpretation of QM you have, the Copenhagen or Bohm etc.

3. there is a distinction between interaction and observation.

1. we don't look with our eyes on the experiment, the electrons etc are too small to be seen with our eyes, therefore the need of advanced apparatus

4. it depends on your hamiltonian which is the generator of time translations.

 

[Entropia]

I can provide some insights into the concept of measurement in quantum mechanics (QM). Measurement in QM is a fundamental aspect of the theory, and it is essential to understand it for a comprehensive understanding of QM.

1. In QM, measurement is defined as an interaction between a quantum system and a classical macroscopic apparatus. This interaction causes the system's wave function to collapse into a particular state, also known as the "collapse of the wave function." So, in a sense, by looking at an experiment, you are causing the wave function to collapse into a particular state. However, it is not just your observation that causes the collapse, but the interaction between the system and the apparatus.

As for your question about a blind person getting a different result, it is important to note that the collapse of the wave function is a probabilistic process. So, while the blind person may not see the result, the wave function will still collapse into a particular state, and the outcome of the measurement will be determined by the probability of that state.

2. In QM, any interaction with the quantum system can be considered a measurement. So, a conscious mind is not necessarily required for a measurement to occur. For instance, a computer taking and storing readings can also be considered a measurement if it interacts with the quantum system. However, the collapse of the wave function will only occur when the data is retrieved from the computer and observed by a conscious mind.

3. In QM, the concept of observation is different from the classical notion of observation. In QM, observation does not necessarily require a conscious mind or a physical apparatus. Any interaction with the quantum system can be considered an observation. So, in the case of a charged object affecting the electric and magnetic fields around it, it is not considered a measurement in QM.

4. In QM, the collapse of the wave function is a temporary process. Once the measurement is made, the system will remain in that state until the next measurement is made. So, the system will not stay in that state forever, and it can evolve into different states over time. Additionally, the concept of compatible and non-compatible observables is crucial here. If we measure a compatible observable, the system will remain in that state. However, if we measure a non-compatible observable, the wave function will collapse into a different state, and the system will evolve accordingly.

I hope this helps clarify the concept of measurement in Q