How does Classical Physics explain Quantum Entanglement?

  • #1

Main Question or Discussion Point

As a Computer Programmer, it's hard to wrap my head around Quantum Entanglement and non locality being explained in the context of Classical Physics. In other words, if the universe at it's core is physical where does Quantum Entanglement fit within a physical picture of reality?

There's been talks by Physicist like John Preskill that says space-time is a quantum error correcting code. This would mean most of space is physical qubits doing quantum correction to protect any code running on logical qubits.

Is spacetime a quantum error-correcting code?

http://online.kitp.ucsb.edu/online/entangled_c15/preskill/pdf/Preskill_Entangled15Conf_KITP.pdf
http://online.kitp.ucsb.edu/online/entangled_c15/preskill/pdf/Preskill_Entangled15Conf_KITP.pdf
Holographic quantum error-correcting codes: Toy models for the bulk/boundary correspondence

We propose a family of exactly solvable toy models for the AdS/CFT correspondence based on a novel construction of quantum error-correcting codes with a tensor network structure. Our building block is a special type of tensor with maximal entanglement along any bipartition, which gives rise to an isometry from the bulk Hilbert space to the boundary Hilbert space. The entire tensor network is an encoder for a quantum error-correcting code, where the bulk and boundary degrees of freedom may be identified as logical and physical degrees of freedom respectively. These models capture key features of entanglement in the AdS/CFT correspondence; in particular, the Ryu-Takayanagi formula and the negativity of tripartite information are obeyed exactly in many cases. That bulk logical operators can be represented on multiple boundary regions mimics the Rindler-wedge reconstruction of boundary operators from bulk operators, realizing explicitly the quantum error-correcting features of AdS/CFT recently proposed by Almheiri
https://arxiv.org/abs/1503.06237

Here's a paper published by Physicist Paola Zizzi who talks about Computational Loop Quantum Gravity.

Computability at the Planck scale

We consider the issue of computability at the most fundamental level of physical reality: the Planck scale. To this aim, we consider the theoretical model of a quantum computer on a non commutative space background, which is a computational model for quantum gravity. In this domain, all computable functions are the laws of physics in their most primordial form, and non computable mathematics finds no room in the physical world. Moreover, we show that a theorem that classically was considered true but non computable, at the Planck scale becomes computable but non decidable. This fact is due to the change of logic for observers in a quantum-computing universe: from standard quantum logic and classical logic, to paraconsistent logic.
https://arxiv.org/abs/gr-qc/0412076

It makes sense to me to me to design a program where I have random red dots moving around on the computer screen and the program is coded in a way that when a red dot gets entangled with another red dot and I click on that red dot, the red dot it's entangled with turns green. I can then extrapolate my computer screen to the size of the universe and I can click on a red dot on one side of the universe and instantly, the red dot it's entangled with will turn green even if it's on the other side of the universe. So subatomic particles would be like pixels on a space-time screen.

So my question is, how does Quantum Entanglement and non locality fit within a physical model?
 

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  • #3
atyy
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As @Lord Jestocost says, there is no way for classical physics (which local causality) to explain quantum entanglement.

However, if we give up local causality, Bohmian Mechanics provides one suggestion as to how a nonlocal "physical model" could produce quantum entanglement phenomena.
 
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However, if we give up local causality, Bohmian Mechanics provides one suggestion as to how a nonlocal "physical model" could produce quantum entanglement phenomena.
In which way exactly and does it fit better than a computational approach?
 
  • #5
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In which way exactly and does it fit better than a computational approach?
If a classical-like picture is what you want, then Bohmian mechanics fits better than any other (including computational) approach to quantum mechanics. I am not aware that someone wrote something like "Bohmian mechanics for computer programmers", but in my signature below you will find my "Bohmian mechanics for instrumentalists", which might be close enough.
 
  • #6
If a classical-like picture is what you want, then Bohmian mechanics fits better than any other (including computational) approach to quantum mechanics. I am not aware that someone wrote something like "Bohmian mechanics for computer programmers", but in my signature below you will find my "Bohmian mechanics for instrumentalists", which might be close enough.
Interesting read but there's a few problems.

First, I understand why Bell wanted to use the term beables over observables. The fact is, calling subatomic particles, particles is confusing. When you think of particles, you think of particles of sand or particles of salt not Quantum Entanglement, non locality, quantum tunneling or quantum teleportation. So I prefer to call them subatomic states verses particles. As QFT says, they're excitation's in the underlying quantum fields.

In your Summary you said:

In this paper we introduced the notion of perceptibles, which are macroscopic entities that we observe directly. Since perceptibles are macroscopic, they are distinguished in 16 the position space. The non-perceptibles such as wave function, atom, photon, etc. are theoretical constructs that explain the perceptibles. Our main axiom for the perceptibles is that all perceptibles are beables. Essentially, it means that the Moon is there even when we do not observe it. However, there is no strict border between perceptibles and non-perceptibles, which suggests that microscopic positions are beables too. This is the motivation for introducing Bohmian mechanics (BM), according to which particles have trajectories.

But what particles? BM only makes sense if the particle trajectories are trajectories of the fundamental particles. On the other hand, as discussed is Sec. 5.1, there are indications that the Standard Model particles might not be fundamental, suggesting that BM should not be applied to them. Moreover, the simplest version of BM makes a generic measurable prediction; it predicts that the fundamental particles obey non-relativistic QM. Analogy with phonons indicates that fundamental non-relativistic QM may lead to non-fundamental relativistic QFT, which, in principle, bypasses the problem of relativistic BM without knowing the details of those hypothetic fundamental particles.
http://de.arxiv.org/pdf/1811.11643v3

I think the evidence supports a computational, non physical reality vs. perceptibles, beables or non perceptibles. I understand why though, because it makes no sense that anything physical is associated with superposition, tunneling, teleportation, entanglement and more. That's the part I can't wrap my head around. How can the wave function or what we call subatomic particles be physical in any way? Here's a paper published about this:

The wave-function is real but nonphysical: A view from counterfactual quantum cryptography

Counterfactual quantum cryptography (CQC) is used here as a tool to assess the status of the quantum state: Is it real/ontic (an objective state of Nature) or epistemic (a state of the observer's knowledge)? In contrast to recent approaches to wave function ontology, that are based on realist models of quantum theory, here we recast the question as a problem of communication between a sender (Bob), who uses interaction-free measurements, and a receiver (Alice), who observes an interference pattern in a Mach-Zehnder set-up. An advantage of our approach is that it allows us to define the concept of "physical", apart from "real". In instances of counterfactual quantum communication, reality is ascribed to the interaction-freely measured wave function (ψ) because Alice deterministically infers Bob's measurement. On the other hand, ψ does not correspond to the physical transmission of a particle because it produced no detection on Bob's apparatus. We therefore conclude that the wave function in this case (and by extension, generally) is real, but not physical. Characteristically for classical phenomena, the reality and physicality of objects are equivalent, whereas for quantum phenomena, the former is strictly weaker. As a concrete application of this idea, the nonphysical reality of the wavefunction is shown to be the basic nonclassical phenomenon that underlies the security of CQC.
https://arxiv.org/abs/1311.7127

This experiment was realized here.

Direct counterfactual communication via quantum Zeno effect

Intuition from our everyday lives gives rise to the belief that information exchanged between remote parties is carried by physical particles. Surprisingly, in a recent theoretical study [Salih H, Li ZH, Al-Amri M, Zubairy MS (2013) Phys Rev Lett 110:170502], quantum mechanics was found to allow for communication, even without the actual transmission of physical particles. From the viewpoint of communication, this mystery stems from a (nonintuitive) fundamental concept in quantum mechanics—wave-particle duality. All particles can be described fully by wave functions. To determine whether light appears in a channel, one refers to the amplitude of its wave function. However, in counterfactual communication, information is carried by the phase part of the wave function. Using a single-photon source, we experimentally demonstrate the counterfactual communication and successfully transfer a monochrome bitmap from one location to another by using a nested version of the quantum Zeno effect.
https://phys.org/news/2017-05-counterfactual-quantum.html

Here you have information from point A to point B without a physical medium. You have the recent experimental evidence of Wigner's Friend on a quantum level.

Experimental test of local observer-independence

The scientific method relies on facts, established through repeated measurements and agreed upon universally, independently of who observed them. In quantum mechanics, the objectivity of observations is not so clear, most dramatically exposed in Eugene Wigner's eponymous thought experiment where two observers can experience seemingly different realities. The question whether these realities can be reconciled in an observer-independent way has long remained inaccessible to empirical investigation, until recent no-go-theorems constructed an extended Wigner's friend scenario with four observers that allows us to put it to the test. In a state-of-the-art 6-photon experiment, we realise this extended Wigner's friend scenario, experimentally violating the associated Bell-type inequality by 5 standard deviations. If one holds fast to the assumptions of locality and free-choice, this result implies that quantum theory should be interpreted in an observer-dependent way.
https://arxiv.org/abs/1902.05080

Wigner's Friend tells us that Wigner's Friend in the lab can "collapse the wave function" in the H and V basis in the lab and the single photon is no longer entangled. Wigner outside the lab can carry out an interference measurement and he still sees interference and he can assume that his friend in the lab hasn't carried out a measurement.

He gets a call from his friend who tells him he carried out the measurement and the results now Wigner doesn't see interference. This sounds like Bayesian updating and if we were talking about anything Universal, why didn't Wigner's Friend "collapse the interference" for Wigner?

If you look at things like space-time as a quantum error correcting code, quantum logic gates forming around black holes, black hole thermodynamics and the holographic principle, it screams a computational universe.

This would mean, 96 or 98% of space is doing quantum error correction for the information encoded on logical qubits. We could be the 2 or 4% of quantum error correction that has decohered.

A 3-qubit code encodes a single logical qubit into three physical qubits and it can correct for a single, σx, bit-flip error.

The two logical basis states |0>L and |1>L are defined as

|0>L = |000>, |1>L = |111>

Extrapolate that 3 qubit code into all of space doing error correction but this error correction will not be perfect. This could be why space needs to be so vast. You need a lot of error correction to protect information on logical qubits if they're encoding something like the universe. A small percentage will decohere and this could be our universe. So a computational universe seems to make more sense based on recent experiments.
 

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