I.m sorry if it.s a dumb question, probably is 💀, but how does sound come to by from a quantum perspective? Most info I found online is on how sound is made by speakers or by the vocal cords but I guess my question is a bit more micro than that.

So I know space / time can be viewed like a coordinate graph on a flat piece of paper, x for time and y for space. But there’s another (idk the word for it so I’m going to call it a line) there’s ANOTHER line that is coming right up out the paper straight towards your face. And that’s where the imaginary numbers are. Am I on the right track? Also, is this 4D? Thanks I’m dumb but curious

Hey guys, I have been watching Quantum Physics videos for around one year now. Mostly all the theories are fun to know. I don't find it as difficult the memes show or as difficult everybody on the Internet complains it to be. I understand the Maths part must be difficult and I have no idea about mathemetical part but theories are not incomprehensible. What am I missing? Which theory could I possibly not have I watched? Please guide.

Edit 1: Guys, calm down. I never meant to trigger anyone. Neither did I mean that I know it all. Instead what I meant was I am not finding quantum physics difficult so I must be missing something big, help me find it out.

In the "classical MW view" we "start" with a universe, and as soon as quantum particles in superposition begin to “measure” themselves (becoming entangled with the environment), this causes a branch. Over time, these branches increase to inconceivable levels, branching upon branching. In the immediate past, there were fewer branches than in the present, and each present moment gives rise to countless branches. the many worlds.

Now, could we instead conceive of the future (what we traditionally think of as the future) as the superposition of every single possible event (the collection of all possible branches, of all possibile A-B AA AB BA BB etc, all ramification) and the present as the “eye of the needle” through which all these branches reduce to one?

Time would “flow” from the future (where all possible measurement outcomes are in superposition) toward the present’s eye of the needle, where particles become entangled with the environment and decohere

In this way, there would be no actual branches (the universe is always “decohered” in the past, is always a singular outcome; there are no existing many worlds) but only branches in future superposition.

To visualize it metaphorically, imagine a huge, shapeless ball of meat containing every possible fiber (the collection of all the many worlds, the collection of all ramification). Gradually, it is pushed through a grinder (the present measurment, the entanglement and decohrence), from which well-defined meat strands emerge to make hamburger patties stacked one on top of the other (the space-time slices of the past).

Maybe I got carried away with the misleading metaphors, but the technical question is: is the theory of many worlds time-invariant?

https://www.thebrighterside.news/space/revolutionary-new-theory-finally-unites-quantum-mechanics-and-einsteins-theory-of-general-relativity/

Is this physical review x journal a legit one?

I've read a few different papers on Hawking Radiation and noticed discrepancies. First, in Hawking's original letter introducing the concept, in Nature (1974), he describes it as the blue shifting of nodes of waves in a quantum field, so that they no longer cancel out, and thereby produce particles. However when I was reading more recent papers, they describe it similar to the Unruh effect, in that a static observer would observe a thermal radiation, while an accelerating one would not. I also have seen the virtual particle explanation but from what I can tell it seems to be made up by Hawking to sell his book as 1. His original letter doesn't use this explanation nor anything close to it and 2. the black hole should absorb a rougly equal amount of particles and anti particles, so its mass wouldn't change.

Which explanation is correct, and why? Why are there different explanations anyway?

If you shot an electron through a tube that splits into 3 tubes would it take a wave or particle form? Will it A, go down all 3, or B, it will stay as one electron and continue down one if the tubes? If it goes down all 3 then does this mean we can infinity duplicate matter or It is there still only one electron just spilt into probabilities? Wave particles duality is a strange concept, I would like to have a deeper understanding of it. Because the wave experiment makes sense but this one is less clear on an answer and I can’t seem to find anyone who has actually tried something of this nature.

Hello!! I had a couple of questions about the concept of Device Independent Quantum Key Distribution and how exactly Quantum Encryption works, and if I have the correct basic understanding so far. I’m a college student wanting to familiarize myself with this. The point is to have the sender of the sensitive info generate a pair of entangled photons to which they’d keep one pair and the second is routed down to the receiver along the same pathway as the information would. So this is what I don’t understand, when any third party wants to intercept or tune into the transfer, how is it that their act of tuning in disturbs the second photon which in turn disturbs the first? Afterward, the sender knows the data shouldn’t be sent and reroutes the person to some other transaction medium?

I just didn’t get in what way the hackers presence disturbs the photon.

What happens when you know you’re hacked now, will this just be repeated over and over again until there is a secure network?

Can this work anywhere that isn’t a data transfer website where you send things to a recipient, like if someone tapped into my phone, would this system help with that or does it just concern transactions or anything between people online?

If there is anything I’m missing, please let me know!

I genuinely want to learn QM and I have a background in science but there was a gap in my studies. So now I find it so difficult to grasp unlike before. How do I start? I know I'll have to brush up and learn a lot of maths. Please give me a plan.

I'm a high school student with a little to no knowledge of quantum physics but a ton of interest. we learnt about paulis exclusion principal and are currently studying chemical bonding and hybridisation and stuff. i just had a thought and searched it up but didn't get the answers so I came here.

i was thinking that if electrons in the same orbitals must have opposite charge and that while hybridising when we excite an electron and it may or may not change its spin and then bonds with other electron with an opposite spin. does that mean that electrons in the same orbital or electrons that bond are entangled?

Can someone explain to me how a point particle exist. How can something that’s described as a point be a physical object with physical properties, I get leptons, quarks and bosons don’t have any internal structure but what does that even mean and how does that make them “point particles”

I don’t have a strong background in linear algebra and I’m learning independently while taking my quantum physics course. I have a couple of questions.

1. I want to better understand how I can think of manipulating quantum states using unitaries for the purpose of differentiating between the states. Specifically, I don’t have an intuition on when to apply CNOT gates.

2. Now my main question is can I construct a unitary that will map my basis to any basis I want? For example I want to map these states

[ 1 -1 -1 -1], [1, 1, -1, 1], [1, -1, 1, 1], and [-1, -1, -1, 1].

to an orthonormal basis

[ 1 0 0 0 ], [0 1 0 0], [0 0 1 0 ], and [0 0 0 1].

, such that I can differentiate between the four states. How do I approach such a problem?

In the world of quantum mechanics (QM), we have inferred and mathematically described a set of characteristics that are completely unperceivable, incompatible, untranslatable by our senses and cognitive apparatus, even though they can be incorporated into a formal mathematical framework (schroedinger equation, superposition, wave-particle duality etc). These characteristics, in a Kantian sense, are noumena.

When we "measure" or "observe" quantum phenomena through experiments, accelerators, measurment device etc, we are translating them, transposing them into a format that makes them perceivable, compatible, and translatable, apprehensible by our senses and cognitive apparatus. In essence, we are translating them, in Kantian terms, into phenomena.

Translating/transposing/redefining X from conceptual/existential system A to conceptual/existential system B is not something transcendental, particular, or mysterious. Do quantum phenomena change their "behavior" when they are translated compared to when they are not? Evidently, yes—that’s the point of translation: to make something different from what is originally, translated into a form the human brain can process visually and interact with.

is not the wave function collapses when observed or measured, it is simply translated into a format such that consciousness can process it.

I mean, it would be strange the other way around... given that evolutionarily our cognitive and empirical faculties have developed to locate food sources in the savannah, why should we be able to access the world of quantum particles "directly" and with no inter-mediation, translation into comprehensible form?

Is anyone looking into a SIKE wrapped QKD funneled through another pqk using binary in a light wave?

Why is the quantum velocity of a particle half its classical velocity? Is it because the wave packet that is supposed to represent the particle contains a range of k's? What physical significance does it have?

I’ve been reviewing Niels Bohr’s 1958 piece, Causality and Complementarity, and I’m curious if anyone else has explored some of its more intricate points. In particular, Bohr discusses a central problem that led to the quantum formalization: how the state of a physical system is defined by symbolic operations subjected to a non-commutative algorithm involving Planck’s constant. This formalism, he argues, prevents a deterministic, classical description of physical quantities but allows us to determine their spectral distribution through atomic processes.

Bohr highlights that the non-pictorial character of this formalism finds expression in statistical laws tied to observations obtained under specific experimental conditions. To address the ambiguity inherent in quantum experiments, he insists that the experiment must be described in plain language refined by classical physics terminology, since communication of what we have done and learned is essential for the scientific process. Yet, in quantum mechanics, there’s a crucial distinction between the measuring apparatus and the object of study, with the interaction between them forming an inseparable part of the phenomenon itself—something absent in classical physics.

How do we reconcile this non-deterministic formalism with Bohr’s demand for clear, classical language in describing quantum phenomena? Is Bohr suggesting that classical language is sufficient only for the experimental setup and measurement, but not for the phenomena itself?

I need to find energy level correction for a linear harmonic oscillator that is perturbed by a field

Vˆ = γ xˆ6

Can't wrap my head around this problem, maybe someone here can help

I believe that most people who have spent a lot of time looking into Quantum Mechanics have come to some type of idea within their mind of how they describe wave function collapse. I believe the pioneers of Quantum Mechanics anticipated this exact response to their framework. Individuals would try to reconcile the dichotomy of complementarity they worked so hard to create with their own arbitrary boundaries.

John von Neumann described this process as follows:

“The danger lies in the fact that the principle of the psycho-physical parallelism is violated, so long as it is not shown that the boundary between the observed system and the observer can be displaced arbitrarily in the sense given in the measurement problem.”

I argue that each of us is violating the principles of parallelism through our own psycho-physical process to describe the phenomenon, if and only if, we deny that the juxtaposition between the observer and the observed is subjective and cannot be described in empirical terms. There is a fundamental reason why we all can’t agree on the wave function collapse.

Although this will probably be rejected by most people here, however you describe the wave-function collapse is simply arbitrary in the sense of Bohr’s and John von Neumann’s framework they created to establish a rigorous system of describing the quantum world that is all around us. I’m curious if there are others who share this understanding with me, or if each of you has your own arbitrary boundaries that appear to reconcile the problem within your own mental framework?

In the absence of any potential, why does a particle(wave packet) possess a range of energies? Why doesn't it have a fixed value of energy? If there is no potential energy, then how can the kinetic energy of the particle change with repeated measurements? Isn't it a violation of the conservation of energy?

I want to see how this group understands or interprets the connection between Niels Bohr and John von Neumann regarding the measurement problem in quantum mechanics.

I’m currently reading Niels Bohr’s Atomic Physics and Human Knowledge, particularly his discussion with Einstein. Bohr emphasizes a crucial point: there’s an impossibility of sharply separating the behavior of atomic objects from the interaction with the measuring instrument. Bohr’s key argument here is that the conditions under which a phenomenon appears are defined by how we choose to measure it. This is part of his complementarity principle, where what we observe (such as position or momentum) depends entirely on the experimental setup—there’s no pre-existing “reality” waiting to be revealed independently of our measurement.

This made me think of John von Neumann’s Mathematical Foundations of Quantum Mechanics, where he introduces the concept of the “cut” (Schnitt). According to von Neumann, we can place the cut arbitrarily between the quantum system and the classical measuring apparatus, but the measurement process remains the same: at some point, the observer’s interaction with the system causes the wave function to collapse. No matter where you place the cut, the observation itself is what finalizes the measurement, collapsing the system into a definite state.

It seems like both Bohr and von Neumann are pointing to the inseparability between the observed system and the act of observation or measurement. For Bohr, the measurement defines the phenomenon we observe, and for von Neumann, the cut between the quantum system and the observer is fluid—but the measurement still collapses the wave function into a classical outcome.

I’m curious how others interpret the connection between these two views. Are Bohr and von Neumann essentially saying the same thing in different ways? Or do you see important distinctions in their interpretations of measurement and the observer’s role in quantum mechanics?

How can they conclude that non local variables are proven by bells Therom and physics breaks down at the quantum level?

That sounds like a huge leap in logic to me.

To my understanding bell Therom proves 1 of 2 things is write:

1. FTL is not possible
2. We actually don’t understand what matter is.

I’m no scientist so maybe I’m missing something here but it seems super straight forward to me. The only think we can know is that we don’t know. It’s definetly a lot more conceivable that matter is a variable that can be infinite.

"The Fabric of the Cosmos" with Brian Greene (the four-part miniseries) first aired on November 2, 2011. For me and many others, it played a huge role in sparking interest in quantum physics because it did a really good job at explaining things in a way anyone can understand.

I'm curious if this subreddit would be interested in doing a scheduled rewatch this November? There have been some advances in testing certain theories since the series came out, so it could lead to some really interesting group discussions. Since it was a PBS show, it's available to watch for free—at least in the US. I can also try to find ways for anyone outside the States to watch it (maybe even stream via Discord if nothing else).

The whole idea of a scheduled rewatch is pretty common in anime subreddits, and I think the concept could work well here too (maybe?). Just wanted to gauge the interest level.

Was also hoping to eventually start a book club type thing for this eventually but this seems the easiest to dive into right now

Now if an electron is there at an orbit, it has a specific spin opposing the other. But when it goes to a higher exited state, does the spin changes or it remains the same. What it there are two more electrons whose spins are in opposite direction nd are stable. So which spin will the additional electron show? 🤔

Everyone must have that problem that when they saw the solution it was just so illuminating. I for me solving the hydrogen atom is just beautiful, and the physics that it reveals is awesome like quantized energy levels. Also the variational method for solving the ground state of a simple molecule is pretty awesome to see that bonding is actually predicted