The quantum state of the Universe

[accdd]

The dimension of the space of quantum states of multiple particles grows exponentially as the number of particles increases. I would have expected to more likely find the quantum state of many particles in a strange state (such as an entangled one) but it is not so, why? Why isn't the universe entangled? Just because macroscopic objects are continually hit by particles, forcing measurements? If so, then do single particles far away in vacuum (not subject to continuous measurements) evolve towards entangled states? Why isn't the universe in a weird quantum state?
Sorry for the mistakes, i am using a translator.

 

[PeroK]

Why do you think the universe is not in an entangled state? How do you know the universe is not in a "weird quantum state"? Perhaps it is. What is the definition of "weird" in this context?

 

[accdd]

By weird quantum state I mean a state that cannot be expressed as a product of individual particles.
I know the universe is not in a weird quantum state because I have read that if the particles are distant and their respective wave functions do not overlap, we can approximate the wave function of both as the product of the individual wave functions, and this is not a weird quantum state.
If we have distant particles that are not interacting with anything their quantum state should evolve towards a state that is not the product of the individual particles. Wouldn't this create long-distance correlations that are not observed? What is the evidence that the universe is in a "weird" quantum state?

 

[PeroK]

By weird quantum state I mean a state that cannot be expressed as a product of individual particles.

That makes no sense to me. Are you using weird to mean entangled?

What is the evidence that the universe is in a "weird" quantum state?

I don't have a working definition of "weird".

 

[accdd]

If entagnled is any state that cannot be expressed as the product of the states of the individual particles that compose it, then yes. I used the word "weird" because I don't know if either the word entangled is valid for describing states of physically distant particles.

 

[CoolMint]

There are quantum states and there is the Universe. Through measurements, quantum states become the Universe. Obviously, measurements are ubiquitous otherwise you'd have no Universe. Throw in observers or many worlds and the mystery is solved(btw those 2 are the most popular interpretations along with decoherence which also employs many worlds)

 

[A. Neumaier]

The dimension of the space of quantum states of multiple particles grows exponentially as the number of particles increases.

The dimension is countably infinite already for a single particle, and this does not change for multiple particle states. Only in quantum field theories one may have Hilbert spaces with an uncountable dimension.

I would have expected to more likely find the quantum state of many particles in a strange state (such as an entangled one) but it is not so, why? Why isn't the universe entangled? Just because macroscopic objects are continually hit by particles, forcing measurements? If so, then do single particles far away in vacuum (not subject to continuous measurements) evolve towards entangled states? Why isn't the universe in a weird quantum state?
Sorry for the mistakes, i am using a translator.

The state of any large piece of the universe is not even approximately the product of single particle states. This is consistent with the cluster property that asserts that particles far away from each another are asymptotically independent. This makes the 2-particle state approximately the product of two single particle states. But any open, convex part of the universe containing an observer and two far away particles is nevertheless in a very complex multiparticle state.