Undergrad Questions about QFT and the reality of subatomic particles

[Quantum Alchemy]

I've been reading about Quantum Field Theory and what it says about subatomic particles. I've read that QFT regards particles as excited states of underlying quantum fields.

If this is the case, how can particles be regarded as objective? It seems to me that this also removes some of the mystery associated with Quantum Mechanics.

It's often said that QM says, a particle like an electron can be in multiple states at the same time. This is confusing because when people think of a particle, they think of a particle of salt or a particle of sand. So naturally, it's mysterious as to how a particle of anything can be in multiple places at the same time.

With QFT, you remove this notion from the equation and are more in line with saying the particle only exists as potential until a measurement occurs so the potential has to be just as real as the actual. This brings us to the debate about the wave function being real or a mathematical abstraction that represents some underlying reality. My vote is that it's real but non physical as supported by Counterfactual Quantum Cryptography.

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 makes sense in light of QFT and recent experiments.

I see it like an Ocean with small ripples(quantum fluctuations) but at certain points of the Ocean these ripples get excited and turn into large waves(particles, galaxies, universes). We then have to ask what causes the ripples to become waves. If we look at the Ocean analogy, we can say the weather or maybe there's a school of fish or sharks under that point in the Ocean doing something under the water that's causing the ripples on the surface to turn into larger waves.

So it seems to me that the cause of the ripples turning into waves is more fundamental to reality than any particles which are just the end result of this excitation.

 

[PeterDonis]

I've been reading about Quantum Field Theory

Where? Please give references. (You give a link to one paper later in your post, but it doesn't say the things you are saying you read at the start of your post.)

It's often said that QM says, a particle like an electron can be in multiple states at the same time.

No, that's not "often said", at least not in acceptable sources like textbooks and peer-reviewed papers.

What is "often said" is that particles can be in states that are not eigenstates of common observables like position or momentum. That means that if you try to measure those observables for the particle, the result is probabilistic--QM only predicts the probabilities of getting different possible results. But the particle still has just one state; it is not in multiple states at the same time.

QFT is no different from ordinary QM in this respect.

 

[PeterDonis]

I see it like an Ocean...

Please read the PF rules on personal speculation. That's what your post from here on is. Even in this forum, which gives somewhat wider latitude because it is about interpretations and foundations, personal speculation is not allowed.

 

[Quantum Alchemy]

QM only predicts the probabilities of getting different possible results. But the particle still has just one state; it is not in multiple states at the same time.

Where's the evidence that the particle has one state prior to a measurement occurring? Also, it's not speculation, it's an analogy. I'm only describing what QFT says but using an analogy. I didn't know analogies weren't allowed.

QFT says in most places, these Quantum Fields just have small ripples or fluctuations. In the places where energy causes these small fluctuations to become much larger and we see particles and galaxies. So there wasn't any speculation.

In theoretical physics, quantum field theory (QFT) is a theoretical framework that combines classical field theory, special relativity, and quantum mechanics[1]:xi (but notably not general relativity's description of gravity) and is used to construct physical models of subatomic particles (in particle physics) and quasiparticles (in condensed matter physics).

QFT treats particles as excited states (also called quanta) of their underlying fields, which are more fundamental than the particles. Interactions between particles are described by interaction terms in the Lagrangian involving their corresponding fields. Each interaction can be visually represented by Feynman diagrams, which are formal computational tools, in the process of relativistic perturbation theory.

https://en.wikipedia.org/wiki/Quantum_field_theory

My analogy say nothing different than what QFT says. If you think it doesn't than it can be easily corrected using QFT not any speculation.

 

[PeterDonis]

Where's the evidence that the particle has one state prior to a measurement occurring?

This question makes no sense. The particle's state is part of the theory, not the data. The theory always models the particle as having one state. (More precisely, it does as long as the particle is not entangled; entangled particles don't have a well-defined state at all, only the joint system including all entangled particles does.)

it's not speculation, it's an analogy

Sorry, the part of your post that I said was speculation, is speculation. Please note that I didn't say all of your post was speculation, only that part. Saying "it's an analogy" doesn't excuse speculation; speculative analogies are still speculation. Anyway, science does not work by analogy.

I'm only describing what QFT says

No, you're not. You're describing your own personal speculative version of what QFT says.

My analogy say nothing different than what QFT says.

Wikipedia is not a valid source. Go look at a textbook or peer-reviewed paper.

 

[Quantum Alchemy]

This question makes no sense. The particle's state is part of the theory, not the data. The theory always models the particle as having one state. (More precisely, it does as long as the particle is not entangled; entangled particles don't have a well-defined state at all, only the joint system including all entangled particles does.)Sorry, the part of your post that I said was speculation, is speculation. Please note that I didn't say all of your post was speculation, only that part. Saying "it's an analogy" doesn't excuse speculation; speculative analogies are still speculation. Anyway, science does not work by analogy.

First, I haven't read anywhere that a particle exists in one state prior to measurement. Which state exactly and is the one state in many possible state prior to measurement? Any peer reviewed studies that support this would be appreciated.

Again, analogies are used all the time in scientific debates. I don't see anything in your rules that says analogies aren't allowed.

Speculation would be if I said that these excitation's were caused by a parallel universe. I simply gave an analogy on what I think QFT is describing and if others think I'm seeing it wrong they can say you're wrong because QFT says x,y or z. They don't need any speculation to refute my analogy.

 

[PeterDonis]

I haven't read anywhere that a particle exists in one state prior to measurement.

Then you evidently need to go read different sources. You haven't referred to a single textbook or peer-reviewed paper. Garbage in, garbage out.

Which state exactly and is the one state in many possible state prior to measurement? Any peer reviewed studies that support this would be appreciated.

Go read any QM textbook.

analogies are used all the time in scientific debates. I don't see anything in your rules that says analogies aren't allowed.

Analogies based on personal speculation are not allowed, because personal speculation is not allowed.

Speculation would be if I said that these excitation's were caused by a parallel universe. I simply gave an analogy on what I think QFT is describing and if others think I'm seeing it wrong they can say you're wrong because QFT says x,y or z. They don't need any speculation to refute my analogy.

No amount of quibbling about what is and is not "speculation" will help you here. Sorry.

Thread closed.