Breaking down the wave function

[-=Red=-]

Please correct me if I am wrong as I am trying to get a better grasp on this.

As of now my understanding is that my bed is in my room. But according to the wave function it is also "smeared" across other spaces. Therefore my bed is also in the dining room. There is a VERY small chance but none the less it is there. Well since the act of observing breaks the wave the bed appears to be in my room. But that's just me. What about other people? Why is the bed in the same place in their view? They are a totally different observer. Why can't they break the wave having the bed appear in the dining room?

 

[Vanadium 50]

People are not required to be "observers". If you prefer, say "act of measurement".

 

[-=Red=-]

Anyone??

PS: Thanks for the correction Vanadium :)

 

[strangerep]

As of now my understanding is that my bed is in my room. But according to the wave function it is also "smeared" across other spaces. Therefore my bed is also in the dining room. There is a VERY small chance but none the less it is there. Well since the act of observing breaks the wave the bed appears to be in my room. But that's just me. What about other people? Why is the bed in the same place in their view? They are a totally different observer. Why can't they break the wave having the bed appear in the dining room?

Much confusion of this kind vanishes when one abandons the older interpretations
of QM that rely on this view of the wave function with so-called "collapse" by an
act of measurement, and then understanding that the wave function merely
determines a probability distribution.

Trying reading up on the "statistical interpretation", as presented in Ballentine's
textbook "QM - A Modern Development", or (more extensively) in his earlier paper:

L.E.Ballentine, "The Statistical Interpretation of QM",
Rev Mod Phys, vol 42, no 4, (1970), p358.

 

[eaglelake]

Please correct me if I am wrong as I am trying to get a better grasp on this.

As of now my understanding is that my bed is in my room. But according to the wave function it is also "smeared" across other spaces. Therefore my bed is also in the dining room. There is a VERY small chance but none the less it is there. Well since the act of observing breaks the wave the bed appears to be in my room. But that's just me. What about other people? Why is the bed in the same place in their view? They are a totally different observer. Why can't they break the wave having the bed appear in the dining room?

Physics is an empirical science. We describe the results obtained when we do experiments. In quantum mechanics the experimental results are all we have. Your bed is in your room. Period. This is an experimental result that everyone agrees with. The rest of your comments have no experimental basis. Rather they are based on speculation. Can you verify in an actual experiment that your bed is sometimes found in your dining room? Why would you think such a thing? As far as I know beds have never been seen to behave like photons, or electrons, or any other quantum particle. Your bed obeys the laws of classical physics. For beds, the laws of Newton and Einstein work just fine. Even if your bed were a quantum object, you would have to repeat the experiment many, many times with identically prepared beds before finding a bed in the dining room of an identical house. Once you observe your bed in your bedroom, your experiment is over. Your quantum bed will stay put where it is. Quantum theory does not suggest that somehow your bed is also in your dining room. Rest assured, no one will ever see your bed in two places at the same time. Theory gives only the PROBABILITY that an identically prepared bed will be found in the dining room. If the identical experiment is repeated, and a bed is found in the dining room, so be it, but that is not your bed. It is a different one! You do not need people to determine where your bed is found. You can invite others to look in your bedroom with you, but none of you are a necessary part of the experimental apparatus. The wave function for your bed experiment is not “smeared across other spaces”. ( I don’t know what other spaces you are referring to). The wave function is defined in a linear vector space and we use it to calculate probabilities. The wave function does not “break” when you observe the location of your bed. We only need one wave function to calculate the probability function for finding your bed in different locations. It is true that many believe that the wave function “collapses” when the bed is detected. But the wave function is not an observable and its collapse is not an experimental result. No one, to the best of my knowledge has ever seen a wave function or its collapse. And, certainly, the presence of other people will not collapse the wave function. Many others disagree with this, but I am suspicious of things that cannot be verified. That is my personal bias.
Best wishes.

 

[Born2bwire]

Please correct me if I am wrong as I am trying to get a better grasp on this.

As of now my understanding is that my bed is in my room. But according to the wave function it is also "smeared" across other spaces. Therefore my bed is also in the dining room. There is a VERY small chance but none the less it is there. Well since the act of observing breaks the wave the bed appears to be in my room. But that's just me. What about other people? Why is the bed in the same place in their view? They are a totally different observer. Why can't they break the wave having the bed appear in the dining room?

Let's ignore all the confusion that making this a macroscopic problem creates. If I have a quantum system and I make an observation, then the wavefunction collapses onto the state that I just measured. Now, as time passes, the wavefunction can relax and the probability density can start to spread so that if I measured again, it may be in a different state or it could again be in the same state. For example, we start with a system where an atom is excited and we measure it and find that it is still excited. If we allow a passage of time to come and go and measure it again, we may find it still excited or it may have dropped down to the ground state. But everytime we measure it and find it in that excited state, the wavefunction resets itself about that state.

The collapse of the wavefunction affects all subsequent measurements. In fact, if we keep measuring the system fast enough (say at intervals much much smaller than the lifetime of the state) then we can actually extend the life of the state far longer than it should statistically last. These multiple measurements, in a way, would be like if Harry measures the system, walks away, and then Mary comes over and measures the system (but to keep the system stabilized in this manner requires very short time scales between measurements). So if you have a fairly stable system to begin with, then repeated measurements of the system can even increase this stability by successively collapsing the wavefunction back onto the state before it has had enough time to relax so that the state has a statistically significant chance of changing.

So this is one way how different measurements can result in the same result. Now this is different than if we created a 1000 identical systems and measured them all, only once, at the same time. When we do this then we get a statistical spread of observations that should correlate with the probability density of the original system.

This is different from the question of why the bed never moves though. This has more to do with the fact that quantum effects are only significant on a very microscopic scale. When we start allowing large systems (and a bed is a very very LARGE system), then the quantum effects start to diminish and the behavior of the system becomes classical. In the end, the chance that your bed will spontaneously change (whatever that might be) will occur on a negilgible probability. Stuff like ages of the Universe amount of time would have to pass for something to change. Physicists don't like to say it would never happen, they just like to be pendantic but in actuality we are talking about time scales that are unconscionable.

 

[-=Red=-]

Thanks very much for these responses! Everyone!

Edit: I guess there is no "Solved" tag in here.