Can Instruments Alter Wave Functions Across Global Distances?

[bluecap]

What instrument can affect wave function of object?
If wave function doesn't have any locality. Then why can't an instrument here able to access and alter the wave function of any object in the world (and detectable in the other side of the planet)? How do you make such experiments. And what could possibility prevent the possibility of this experiment?

 

[Nugatory]

What instrument can affect wave function of object?

In the mathematical formalism of quantum mechanics, the wave function is an abstract mathematical object (it's the solution to a particular differential equation) so the idea of an instrument affecting it is meaningless. It's like asking what instrument can affect the equation $a(b+c)=ab+ac$.

 

[entropy1]

I wonder a bit about this too. If we have a collapse of the Singlet state, what is "caused" is the correlation between the measurements, right?

 

[DrChinese]

What instrument can affect wave function of object?
If wave function doesn't have any locality. Then why can't an instrument here able to access and alter the wave function of any object in the world (and detectable in the other side of the planet)? How do you make such experiments. And what could possibility prevent the possibility of this experiment?

In a limited (and somewhat semantic) sense, it can. Clearly the influence of a distant object on a measuring device here (perhaps a photon detector) would be vanishingly small. And in fact in many cases would likely cancel out entirely and you would see nothing - ever.

If you did detect something (in some rare case), that would in fact mean that the photon was not detected elsewhere. But you would have no good way to know that. In effect, many small particle (wave) probabilities are overlapping at all times.