# How Can Entanglement Emerge If the Universe Is a Single Pure Universal Wave Function At the Most Fundamental Level?

If we accept the idea that only one pure universal wave function exists, as proposed by Hugh Everett and supported by H.-Dieter Zeh, Bryce de Witt, and even John Wheeler for some time [1–3], the question arises what causes the universal wave function to split into Everett’s relational branches in the first place? Is it some sort of an internal split or the entire wave function of the world splits into two identical functions like a single photon splits into two selves in some recent experiments [4]?

From the orthodox interpretation of quantum mechanics we borrow a very simple explanation of the origin of such a split [5,6]. An experimenter isolates a physical system of interest from the measuring apparatus, representing the rest of the world, mentally and, if necessary, also physically.

According to Everett and his proponents, the universal wave function is the only physical object that fundamentally exists [1–3]. Therefore only it can be isolated from the measuring apparatus. However there’s only one measuring apparatus as well — the same universal wave function.

It looks like the only split that is available for the universal wave function is the split into two selves with one observing the other, or in other words two identical wave functions mirroring each other: the universal wave function and its complex conjugate.

As only the left side of Schrödinger’s equation contains an imaginary number, the complex conjugate will change its sign to opposite also only in the left side of its equation compared to the original. The right part containing the time variable will not be changed. It can be interpreted as the wave function and its complex conjugate are evolving both in the same direction in time but are having something akin opposite spins as if they are rotating in opposite directions. Variables of the two functions don’t have definite values but they are rotating (or fluctuating) in opposite directions.

If we now imagine that the universe begins to physically interact with itself in order to complete the measurement such an interaction will lead to entanglement of the two selves of the universe with each other. Actually, if we assume that the universal wave function is a physical system then its interaction with itself will be exactly that physical interaction that causes entanglement.

According to Schrödinger, entanglement begins with the product of wave functions of the systems which are getting entangled [7]. Such a product of the wave function of the universe and its complex conjugate is an absolute square of the wave function of the universe.

Mathematically with an absolute square of a wave function we obtain probabilities of observation of definite values of its variables [8].

Kinematically we obtain a superposition of two blurred snapshots imposed over each other. It shows us all definite values which can be observed but doesn’t say anything about exact timing of observations. Now time is blurred and allows us to see only probabilities of observing a definite value at a definite time.

When self entanglement begins two functions with sets of variables rotating in opposite directions clutch together and get jammed but time keeps going. The connection between evolution of variables and the advancement of time gets broken. Therefore we can’t obtain exact timing of observations of definite values.

As soon as the measurement is completed by the wave function of the universe choosing the branch for its resurrection the entanglement gets lifted (Schrödinger’s term) and the evolution of the resurrected pure wave function resumes rotating in either one or the other direction. The resurrection will take place based on the selected definite value obtained by the measurement. It means that the resurrected wave function of the universe will not be exactly the same as it was prior to the measurement. The definite result of the measurement gets automatically recorded in the new wave function (actually two wave functions which get both restored) [7].

Self entangled universal wave function sets the background. There are no branches inside it. There are only patterns on its surface which change under the influence of the continuous flow on the surface of which they appear.

And so the classical world emerges. The stage for the reality show is set by self entanglement of the universal wave function. It’s waiting for decorations and actors to appear and the show will begin.

# References:

- Everett, Hugh, The Theory Of The Universal Wave Function, The Many-Worlds Interpretation of Quantum Mechanics, Princeton University Press Princeton, New Jersey, 1973
- Zeh, H.-Dieter, The strange (hi)story of particles and waves, 2018, arXiv:1304.1003v23 [physics.hist-ph], https://doi.org/10.48550/arXiv.1304.1003
- Päs, Heinrich. Can the Many-Worlds-Interpretation be probed in Psychology? 2017, arXiv:1609.04878v2 [quant-ph], https://doi.org/10.48550/arXiv.1609.04878
- X.-F. Qian, K. Konthasinghe, S. K. Manikandan, D. Spiecker, A. N. Vamivakas, and J. H. Eberly. Turning off quantum duality. Phys. Rev. Research
**2**, 012016(R) — Published 15 January 2020 - Neumann, John von, and Robert T. Beyer. Mathematical Foundations of Quantum Mechanics: New Edition. Edited by Nicholas A. Wheeler. NED-New edition. Princeton University Press, 2018. https://doi.org/10.2307/j.ctt1wq8zhp
- Heisenberg, Werner. Physics and Philosophy — The Revolution in Modern Science. 1958. Harper & Brothers Publishers, New York.
- Schrödinger, Erwin, The Present Status of Quantum Mechanics, Die Naturwissenschaften 1935. Volume 23, Issue 48.
- Zeilinger, Anton. On the Interpretation and Philosophical Foundation of Quantum Mechanics. (2008).