MWI for simultaneous events

In summary, according to MWI, when two independent experiments are taking place, there are four branches or "worlds" in the "multiverse", each representing one of the four possible combinations of outcomes for the two experiments. The state of the "multiverse" before measurement is the tensor product of the two individual states, and each machine does not know the outcome of the other machine until the measurement takes place.
  • #1
Abdullah Naeem
4
0
Suppose there are two independent experiments taking place [itex] \left\vert \Phi\right\rangle =\alpha _{1}\left\vert \phi _{1}\right\rangle +\beta_{1}\left\vert \phi _{2}\right\rangle [/itex] and [itex]\left\vert \Psi \right\rangle=\alpha _{2}\left\vert \psi _{1}\right\rangle +\beta _{2}\left\vert \psi_{2}\right\rangle [/itex]. According to MWI, when [itex]\left\vert \Phi \right\rangle [/itex] is measured, there are two "branches" of the world, one for each [itex]\left\vert\phi _{i}\right\rangle [/itex]. Similarly, for [itex]\left\vert \Psi \right\rangle[/itex]. My question is, what happens when a measurement for each [itex]\left\vert \Phi\right\rangle [/itex] and [itex]\left\vert \Psi \right\rangle [/itex] takes place simultaneously? As I see it, there are two worlds, one for each [itex]\left\vert \Phi \right\rangle [/itex] but for these worlds but in these worlds, what happens to [itex]\left\vert \Psi \right\rangle[/itex]? Is it that, in these two worlds, [itex]\left\vert \Psi \right\rangle [/itex] has not taken place?
 
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  • #2
In this case the full state of the "multiverse" is ##\left\vert \Phi\right\rangle\left\vert \Psi \right\rangle##. If you do the multiplication explicitly, you will see that it contains 2x2=4 branches (4 "worlds").
 
  • #3
Demystifier said:
In this case the full state of the "multiverse" is ##\left\vert \Phi\right\rangle\left\vert \Psi \right\rangle##. If you do the multiplication explicitly, you will see that it contains 2x2=4 branches (4 "worlds").

Thank you for your reply.
So the state of the world before measurement is [itex]\left\vert \Phi
\right\rangle \left\vert \Psi \right\rangle =\alpha _{1}\alpha
_{2}\left\vert \phi _{1}\psi _{1}\right\rangle +\alpha _{1}\beta
_{2}\left\vert \phi _{2}\psi _{1}\right\rangle +\beta _{1}\alpha
_{2}\left\vert \phi _{1}\psi _{2}\right\rangle +\beta _{1}\beta
_{2}\left\vert \phi _{2}\psi _{2}\right\rangle [/itex]. Four possibilities, right.
So, according to MWI, there will be four branches. I think my confusion
comes in the tensor product. I am thinking of two machines, [itex]\Phi [/itex] and [itex]
\Psi [/itex], each of which will enter two worlds. For the first machine [itex]\Phi [/itex],
the outcomes are either [itex]\left\vert \phi _{1}\right\rangle \left( \alpha
_{2}\left\vert \psi _{1}\right\rangle +\beta _{2}\left\vert \psi
_{2}\right\rangle \right) [/itex] or [itex]\left\vert \phi _{2}\right\rangle \left(
\alpha _{2}\left\vert \psi _{1}\right\rangle +\beta _{2}\left\vert \psi
_{2}\right\rangle \right) [/itex]. How does it know that the other outcome is
either [itex]\left\vert \psi _{1}\right\rangle [/itex] or [itex]\left\vert \psi
_{2}\right\rangle [/itex]?
 
  • #4
The first machine does not know that the second machine must have one of the two outcomes. But the "world" consists of both machines together. If you are interested in only one machine, then you cannot call it a "world".
 

1. What is MWI for simultaneous events?

MWI (Many Worlds Interpretation) for simultaneous events is a quantum mechanical interpretation that suggests there are multiple parallel universes that exist simultaneously. According to this interpretation, every time a quantum event with multiple possible outcomes occurs, the universe splits into different branches, with each branch representing a different outcome. This means that all possible outcomes of a quantum event are realized in different parallel universes.

2. How does MWI for simultaneous events differ from other interpretations?

MWI for simultaneous events differs from other interpretations, such as the Copenhagen interpretation, by suggesting that all possible outcomes of a quantum event are equally real and exist in parallel universes. In contrast, the Copenhagen interpretation suggests that the wave function of a quantum system collapses upon measurement, resulting in only one outcome being realized in the actual world. MWI also differs from the pilot-wave theory, which suggests that particles have definite positions and trajectories, but this theory has been largely abandoned due to experimental evidence.

3. What is the evidence for MWI for simultaneous events?

There is currently no direct evidence for MWI for simultaneous events, as it is difficult to test or prove the existence of parallel universes. However, MWI is consistent with the predictions of quantum mechanics and has been used to explain various quantum phenomena, such as the double-slit experiment and quantum tunneling. Additionally, some physicists argue that MWI provides a more elegant and simpler explanation for these phenomena compared to other interpretations.

4. Are there any criticisms of MWI for simultaneous events?

Yes, there are several criticisms of MWI for simultaneous events. One of the main criticisms is that it is an untestable theory, as the existence of parallel universes cannot be proven or disproven. Additionally, some argue that MWI violates Occam's razor, which states that the simplest explanation should be preferred. MWI also raises philosophical questions about the nature of reality and the role of consciousness.

5. How does MWI for simultaneous events impact our understanding of the universe?

MWI for simultaneous events challenges our traditional understanding of the universe as a single, deterministic entity. It suggests that there are countless parallel universes where different versions of events and outcomes exist simultaneously. This interpretation also raises questions about the nature of time and the concept of free will. While MWI is a controversial and unproven theory, it continues to spark debate and inspire new ideas in the scientific community.

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