[Article] QM's famous Many World Interpretation

[EternalBlizzard]

Hi guys. So its been quite a while since my last article on QM. I was too busy due to my semester exams so im writing about Many-Worlds Interpretation now. Im pretty much out of shape now Anyways hope you guys enjoy it.

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Before i go on about MWI im gonna talk about Hugh Everett's Relative State Formulation. Actually MWI and many other interpretations such as the Many Minds are somewhat derived or you can say attempts to reconstruct Everett's theory because of some gaps left in it and because he didn't clearly explain what he meant. Relative State Formulation was Everett's doctoral thesis in 1957. He was troubled by the so called measurement problem and the wave-function collapse and thus created his theory which had no collapse in it. As a quick reminder..

• Before observation the system is continuously and deterministically evolving through time and is in a superposition of several states.
• As soon as the observation is made, the system collapses i.e probabilistically falls into any one of the states. A discontinuous, probabilistic evolution.

Let's conduct an easy experiment i found on a site in order to explain what Everett wanted to say. Suppose an observer "O" intends to measure the spin of a spin-1/2 system or particle "P" i.e the particle can only have spin up or spin down ( or you can say sping +1/2 and spin -1/2) along x-axis. The particle is in a superposition of 2 states.

• P spin up
  
• P spin down

Spoiler: show

Everett's Relative-State Formulation of Quantum Mechanics (Stanford Encyclopedia of Philosophy)
3. Everett's proposal contains the experiment in much greater detail.

Now according to collapse theories as soon as the observer measures the particle's spin it collapses to either spin up or spin down. The end result would look like..

(O measures spin up, P spin up) OR (O measures spin down, P spin down)​

But Everett proposed that this collapse doesn't happen. He proposed that when an observer measures the system it becomes entangled with it. Before we go on let's understand what entanglement is.

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If 2 systems say "A" and "B" are entangled then this means you can't define absolutely the state of a sub system (either A or B). You can only define the state of the system absolutely as a whole. For example let's say a pair of electrons or photons are entangled. For electrons suppose the total spin was zero then this means one has spin +1/2 and the other one has spin -1/2 while for photons it has something to do with vertical/horizontal polarization, for the time being think of the photons above as electrons. Together the spins cancel out each other and that's how 2 electrons occupy a single orbital if you remember. Before measurement both the electrons are in a superposition of the spin +1/2 and spin -1/2 states. Now we can't absolutely define the state of a single electron. Measurement on entangled systems are correlated i.e observing one subsystem would cause a change or should I say collapse the superposition of the states of the other. If one is +1/2 the other one would definitely be -1/2. But we know for sure that as a whole system their spin would be zero.Coming back to the topic, this meant that after measurement the observer became entangled with the particle and this entangled system, lets call it a composite system "S" (observer + particle) was in a superposition of states. These states would be....

(O measures spin up, P spin is up) + (O measures spin down, P spin is down)​

Notice the "+" sign. This indicates that its in superposition and the important thing to note is that its AFTER MEASUREMENT. All right if it's still in superposition then how come we get a single determinate result? Either up or down.Now here comes the tricky part which my puny mind did its best to comprehend. I'll try to explain as much as i understood. Everett said, since 'O' and 'P' now form an entangled system, its pointless to absolutely define the state of a sub-system ( remember we are interested in the particle). The state of the particle is relative to the state of the observer. Hence the name "Relative State Formulation". But the fact still remains that in reality we get a single determinate outcome. What i was able to comprehend was that observers are in superposition but are unaware of it. Now although objectively speaking the entangled system 'S' is in a superposition of states and 'O' has no determinate record whether spin is up or down but relatively 'O' has a determinate record. Because if we imagine 'P' in state "P spin is up" then relatively it is determinate that 'O' will be in state "O measures spin up". So subjectively an observer thinks he has a determinate record and that wave function has collapsed because he isn't aware that he is in superposition while objectively, no collapse has occurred and the wave function is still in superposition. That was the Relative State Theory of Hugh Everett. I know right, i too wanna say (wtf)


Now MWI was given by Dewitt. Some sites say it was given by Everett while some say Everett never spoke of many worlds. The concept is similar to Hugh Everett's theory though. Before we go further I want to draw your attention on the topic of "What is the difference between universe and a world". While many sites loosely say "universe" splits into branches or something like that, so far what i have gathered, that's wrong. The Universe is one. World is the totality of all the particles. Universe can contain many worlds. We can think of Universe as the space that contains many worlds. In MWI the role of the observer has vanished. Everything apart from the observer and system is the environment. Whether it be an apparatus or conscious human being, when anyone tries to interact with the system it becomes entangled with it. The apparatus in turn is entangled with the world/environment because if we view everything in terms of atoms and molecules, air molecules keep bumping into the apparatus. In MWI the concept of decoherence has great value. Whenever something interacts with the quantum systems information from the system is lost to the environment and this is decoherence. When this happens the Universe branches into many worlds for all the possible states. This Universe has a wave-function known as the universal wavefunction which never collapses. It's a superposition of all the worlds that have branched and are yet to be branched.

One interesting thing I came upon while researching was "Who am I?". Im gonna copy paste directly from there.

“I” am an object, such as the Earth, a cat, etc. “I” is defined at a particular time by a complete (classical) description of the state of my body and of my brain. “I” and “Lev” do not refer to the same things (even though my name is Lev). At the present moment there are many different “Lev”s in different worlds (not more than one in each world), but it is meaningless to say that now there is another “I”. I have a particular, well defined past: I correspond to a particular “Lev” in 2012, but not to a particular “Lev” in the future: I correspond to a multitude of “Lev”s in 2022. In the framework of the MWI it is meaningless to ask: Which Lev in 2022 will I be? I will correspond to them all. Every time I perform a quantum experiment (with several possible results) it only seems to me that I obtain a single definite result. Indeed, Lev who obtains this particular result thinks this way. However, this Lev cannot be identified as the only Lev after the experiment. Lev before the experiment corresponds to all “Lev”s obtaining all possible results. (source is given above)

Do note that MWI is deterministic as there is no role for probability as all possible outcomes are true. One interesting argument against MWI was, from where does the energy to create multiple worlds come from? Didn't research much into this but one answer was don't to think the splitting of the worlds in MWI as branches of a tree but instead as a rope. If one event can cause several outcomes, one outcome can have several causes too. So think of it as unbranching into the past. In that way somehow energy is conserved. For example the above picture maybe wrong. Here if you imagine as a rope, then as a little strand combines with smaller ones then make a bigger one in the same way many causes lead to one single outcome as opposed to the usual thinking that one cause will have several outcomes.

Im going to provide links below for those who want to further research on the topic.

I was hesitating to discuss this topic but i think im going to discuss it anyway. Personally i think, we need more Muslims researching on that topic. I think we can easily thin out most of the theories out there and research the one that conforms most with Islam. For e.g there is a consequence of MWI that all possible futures and histories are real ( in different worlds). Although i have yet to know how because the universe branches only in quantum experiments (that's what i think. If someone can clear that up, all the better) So if that consequence is true then i don't think MWI conforms with Islam. As thinking back it could mean Muslims lost the battle of Badar in one world? It could mean all sorts of things. Another great argument could be the Quantum Suicide thought experiment. If you setup a gun pointed at you in a quantum experiment so that each time the apparatus measures spin up, the gun fires and vice versa. The probability is 50/50 that the apparatus gets spin up or down. So each time the apparatus measures the spin, the universe branches into 2 worlds. One in which you are dead and another in which you are alive. Keep on doing that and you will be quantumically immortal :crazy:

This experiment supports MWI rather than Copenhagen because supposing we believe C.I then there is a probability whether the gun fires or not. If you know basic probability.. then given the no of trials and the probability the outcome (given the events are independent), the probability that the outcome occurs on every trial is (probability of the outcome)^no of trials.
So if i perform the experiment 100 times and still find myself alive then its not just a coincidence since the probability to be alive after 100 trials is (0.5)^100 = very small where as if MWI is true then there is a 100% chance that i am alive because all possible outcomes are true. In other words i must be in a parallel world line rather than "kept on surviving by chance" as C.I. interprets. More detailed in the last link provided below.

Spoiler: show

Q: According to the Many Worlds Interpretation, every event creates new universes. Where does the energy and matter for the new universes come from? | Ask a Mathematician / Ask a Physicist
Why the Many-Worlds Formulation of Quantum Mechanics Is Probably Correct | Sean Carroll
The Everett Interpretation
Quantum Suicide: How to Prove the Multiverse Exists, in the Most Violent Way Possible

Thanks for reading guys. I admit this might not be as good as my previous ones as this was too serious :s
If you watch anime then you should watch Steins Gate and Noein: Mou hitori no kimi e for some quantum fantasy Both are epic

 

[Jester]

Holy wall-o-text. Gonna read this when I wake up tomorrow.

 

[EternalBlizzard]

Holy wall-o-text. Gonna read this when I wake up tomorrow.

I was surprised when i researched, QM isn't just physics and maths... its everything.. its a mixture of physics, maths, statistics, logic philosophy and many of its branches such as ontology and epistemology etc. It's just pure knowledge. That's why i guess people have difficulty in understanding and researching QM... if you are a physicist, you may find yourself limited by statistics. Each and every person is trying to come up with its own idea Plus there are many vague questions raised in QM such as what is reality? Who are we? What is knowledge? and that amazes me

When i start writing about it.... i just can't control it There's so much to discuss...

 

[goats]

for me i guess its like multiple frames of our existence and we exist in those frames as frames of a video clip.
currently we are in one frame and our future is another frame as was our past
but there could be multiple movies/video clips of our lives
its like modern gopen world games our decisions give way to multiple futures
but which one do we live?
and what about the others we dont live?
what happens to the the 'guy' who ends up dead or the 'guy' who ends up being a billionaire cause of a decision that 'guy' took today?

 

[Gizmo]

Great work as always, and also as always I didn't necessarily get it. :crazy:

I completely disagree with the last bit though, we don't need science to conform with religion and religious teachings. Better to look at science objectively and with a clean slate, i.e without your beliefs steering you into a particular direction. Just my two cents.

 

[EternalBlizzard]

Great work as always, and also as always I didn't necessarily get it. :crazy:

I completely disagree with the last bit though, we don't need science to conform with religion and religious teachings. Better to look at science objectively and with a clean slate, i.e without your beliefs steering you into a particular direction. Just my two cents.

I don't get it too though, Im just telling what i understood xD Anyways what exactly you don't understand.. I might try to explain in another way?

Addressing the last part. I ain't any religious scholar and i don't consider myself with ample knowledge about our religion but i will still argue that I think that's the reason why we are lacking in science. We think our religion and modern science are 2 different things when they aren't. Quran is a source of knowledge brah, not just "religious" knowledge. If you try to find the answer you can. If you can't then you aren't finding hard enough. If your beliefs ARE steering you into a particular direction, i don't think it can be wrong... it must be right. I seriously think Muslims have an advantage in the field of science.

Plus Quran has many references to biology and astronomy in it. There are scientist who were amazed when they studied Quran. Take a look at this site.
Scientists On The Qur'an

 

[Jester]

Gave it a look. Interesting read but your formatting is in dire need of fine tuning. I had a hard time telling where something was ending and something new was beginning. Also, some pictures or diagrams would really work well in supplementing the text, kinda like you did with the previous article. Especially in cases where there's anything that needs to be visualized, since I had to do several double-takes to see if I had misread something. It will also help articles with somewhat prosaic subject matters as this seem more palatable.

Good call on linking sources at the end, though. Keep it this way for future articles.

I was surprised when i researched, QM isn't just physics and maths... its everything.. its a mixture of physics, maths, statistics, logic philosophy and many of its branches such as ontology and epistemology etc. It's just pure knowledge. That's why i guess people have difficulty in understanding and researching QM... if you are a physicist, you may find yourself limited by statistics. Each and every person is trying to come up with its own idea Plus there are many vague questions raised in QM such as what is reality? Who are we? What is knowledge? and that amazes me

When i start writing about it.... i just can't control it There's so much to discuss...

I admire your gumption.

 

[EternalBlizzard]

Gave it a look. Interesting read but your formatting is in dire need of fine tuning. I had a hard time telling where something was ending and something new was beginning. Also, some pictures or diagrams would really work well in supplementing the text, kinda like you did with the previous article. Especially in cases where there's anything that needs to be visualized, since I had to do several double-takes to see if I had misread something. It will also help articles with somewhat prosaic subject matters as this seem more palatable.

Good call on linking sources at the end, though. Keep it this way for future articles.

That's the main problem here :s As you start going deeper in QM its all about how good your imagination is. That's why most of the experiments done are thought experiments as the Quantum suicide experiment or Schrodinger's cat experiment there. You will hardly find any pictures that will help make you understand a concept. The last one had pictures because of the famous Double Slit Experiment. This one is more, you can say, philosophy than science. But i'll admit it can use some pictures to help better visualize. I'll try fixing the format and adding pics. Thanks for the feedback