Is there a 'decision time' for quantum states to become fixed?

[BernieM]

I have posted several other silly questions on these forums before, but am hoping this one isn't.

It occurred to me in a real way the other day that I am not interacting with the rest of the universe 'now', as in the absolutely present moment in time. That due to the speed of light restriction in the universe, all that I observe and interact with is 'in the past' measured in my reference frame of time.

When it comes to quantum situations such as schroedinger's cat, where the cat is both dead and alive until its observed, when such an observation does occur, is the state instantaneously set (dead or alive) or is there a 'decision time' for the cat to go from the limbo state to a fixed state due to the fact that nothing (at least I believe) should happen absolutely instantanously?

In other words does the state of the cat become set at the SAME moment in time in reference to the observer AND the cat?

 

[QuantumClue]

When the cat is said to be dead or alive, it really is taken as a real time phenomenon. At that moment, the cat truly is dead or alive according to this way of thinking, until a real time measurement is performed on the cat to ascertain whether it exists in the dead state or the alive state.

Real time measurement just means in this sense, until you perform that observation on the cat, the cat is in a superpositioning of states. Then when the act of measurement takes place, the system is pulled out of the superpositining, or atleast, this is what schrodingers cat says.

The fact you can pull the cat out of superpositioning instantaneously with the act of a measurement, just means that. A state of the cat is evaluated in real time. Real time measurements are things we do.

 

[BernieM]

In particle wave duality, when a particle's position is measured the wave function collapses. Is this collapse 'instantaneous' or does it take some fleeting moment of time?

 

[QuantumClue]

In particle wave duality, when a particle's position is measured the wave function collapses. Is this collapse 'instantaneous' or does it take some fleeting moment of time?

Completely instantaneous.

 

[vanesch]

In particle wave duality, when a particle's position is measured the wave function collapses. Is this collapse 'instantaneous' or does it take some fleeting moment of time?

Completely instantaneous, violating relativity in doing so BTW, but without observable violations of relativistic causality if the underlying quantum dynamics is relativistically invariant.
It is one of the main critics on the collapse as a physical phenomenon which fuel the interpretation debates.

In *practice* it works.