Quantum mechanics is often framed in terms of intrinsic randomness, where uncertainty isn’t just a matter of incomplete knowledge (epistemic) but a fundamental feature of reality itself (ontic). But how confident should we be that this interpretation is correct?

The Key Distinction:

•	Epistemic Uncertainty: Lack of knowledge about an underlying deterministic reality. Think of a die roll—we don’t know the outcome in advance, but if we had all the relevant variables (force, angle, air resistance), we could predict it.

•	Ontic Uncertainty: Reality itself is fundamentally indeterminate. No hidden variables—quantum states are genuinely probabilistic in nature.

The Problem: Are We Confusing the Two?

Most of quantum physics today assumes ontic uncertainty, particularly with the standard Copenhagen interpretation. But let’s take a step back:

•	Bell’s theorem rules out local hidden variables, but does that necessarily mean all uncertainty is ontic?

•	Pilot-wave theory (Bohmian mechanics), a deterministic alternative, produces the same predictions as standard QM but treats uncertainty as epistemic.

•	Quantum Bayesianism (QBism) argues that quantum states are just a tool for updating our personal beliefs, shifting uncertainty back into an epistemic framework.

Open Questions:

1.	If uncertainty is truly ontic, then why does the universe obey precise mathematical laws at all? Why should probability distributions follow rigid rules instead of varying unpredictably?

2.	Could quantum uncertainty be a sign that we’re missing a deeper layer of deterministic structure?

3.	Is it even meaningful to separate epistemic from ontic uncertainty, or is the distinction itself flawed?

Physicists lean toward ontic uncertainty, but historically, science has often mistaken practical limitations in knowledge for fundamental randomness. Could quantum mechanics be another case of this?

Curious to hear thoughts—are we too quick to assume fundamental indeterminacy? Or is the randomness in QM truly baked into reality itself?

Hi I am a bachelors student in Berlin. I am doing BSC Computer Science. I want to pursue masters in quantum physics. I have studied general relativity theory and quantum physics including the schrödinger equation and the Maxwell's 4 equations integral and differential forms through 1 year course in my home country. The course was also computer science but it had physics as a main subject. How can I study physics or specially quantum physics in Berlin so I could presue master in quantum physics

I recently read an article about negative time. I don't remember the entirety of the article, but there was an experiment that resulted in negative time. Which brings me here, im new to reddit and I'm curious if there's anyone here that has better understanding of time in relation to quantum particles...? I'm not sure if I'm asking the right question, but is it possible that with negative time (not time travel) is it far fetched to think time can stop if it's not being observed..?

My entire life I've loved physics and the concept of physics. Potentially later on in life I'd love to get into quantum computing, but I'm not keen on going to university or anything right now.

I want to start diving myself into the world of quantum mechanics.

Does anyone have any books, audiobooks, videos, series, anything educational that they'd recommend?

I studied physics in highschool, and done a bit of self study. I just want to dive in further. I'm so interested.

Thomas Campbell basically says that the wave pattern is a product of our simulated reality. This is the first explanation I’ve heard of why this happens. Please share your thoughts and correct my errors along the way. Thanks have a great day.

I have very little knowledge of quantum physics however I am reading a book and the author says electrons change from wave to particle when observed. But if they are one way when no one is looking…how does one know? Wouldn’t someone have to be observing in order to know?

My question is regarding the delayed choice quantum eraser experiment:

https://en.m.wikipedia.org/wiki/Delayed-choice_quantum_eraser

I have been told on this subreddit that the signal photons with entangled idler photons that hit D3 and D4 do actually interfere with themselves, but that no interference pattern can be reconstructed at D0 in relation to the photon hits at D3 and at D4 because it is not possible to measure for each signal photon that has an entangled idler photon that hits D3 or D4 both the which-way information and a coherent phase relationship necessary for an interference pattern to be discovered across the full set of signal photons that have entangled idlers that hit D3 or D4 respectively as an aggregate. I am not sure about this as it seems to fly in the face of everything demonstrated by the standard double-slit experiment, where the photons are automatically coherent due to the absence of a BBO, yet don't seem to interfere with themselves when which-path information is measured. Is the interpretation of the results of the delayed choice quantum eraser experiment I have presented above correct? I just want some second opinions on this.

To clarify, I do of course understand that an interference pattern can be reconstructed at D0 in relation to the photon hits at D1 and the photon hits at D2. I am asking in this question specifically about whether signal photons that are entangled with idlers that hit D3 or D4 interfere with themselves as well, and whether complementarity simply conceals this when which-way information is present.

Hi there, amateur here — hoping this isn’t a waste of anyone’s time.

As a consequence of the principle of locality /local causality, have any physicists defined "the present" as the region surrounding an observer where decoherence has occurred?

I came across the notion that the future is probabilistic, the past is deterministic, and the present is the moment of transition, collapse, or (more elegantly) decoherence. I hope that's not too hand-wavey.

Building on that notion (and acknowledging that causality propagates over time), could we conceptualize an "emerging causal network" or "bubble of now," local to the observer, where particles have decohered relative to the observer? Crucially (in my speculative view), this bubble wouldn't just be a simple sphere or light cone but affected by nearby superpositions — like unobserved cats or qubits — with those effectively remaining part of the future.

If this interpretation holds, I find it fascinating that quantum objects* might literally shape the present, challenging our classical intuitions.

Does this view align with any existing work? Thanks in advance for your time and insights.

*I imagine black hole event horizons and relativistic horizons would also qualify.

If you're a high-schooler or a 1st/2nd-year undergraduate who’s intrigued about how quantum computing and quantum physics work, then the "BeyondQuantum: Introduction to Quantum and Research" programme by ThinkingBeyond Education may just be the perfect opportunity for you.

It is an immersive twelve-week online programme running from March-May for highschoolers and undergrads across the globe to learn about the maths, physics and coding of quantum computing, plus what STEM research is like.

Video introducing BeyondQuantum ... https://youtu.be/0H7mReDZpVg?si=NkNjXYlBeMudxKB-

and all the details about how to apply... https://youtu.be/OsgqC_wa01Y?si=w1xXH5DOyZiFPOLf

See more info about the schedule, programme structure, and last year's iteration on the main site: https://thinkingbeyond.education/beyondquantum/

For questions, contact info@thinkingbeyond.education  (or comment below).

[*Applications close on January 31st 2025]

I’ve been reading a lot of dissertation papers lately about quantum physics and just wanted to know what type of math do I need to start out with to get into quantum physics what tools do I need to be efficient in?

The Observer effect doesn't prove quantum Superposition

Because the particles don't physically exist in multiple locations,

It's just impossible to observe them (with tools that interfere with their movements) in a way that wouldn't affect their movements, Like opening a door and letting in a draft.

However there are still other experiments that suggest quantum Superposition but not in the commonly used observer effect narrative?

(I couldn't find a layman's explanation for these experiments so I am woefully lost)

No AI. You need to be able to speak for yourself. Whatever you copypaste from a LLM is not interesting, and it's not you. We're interested in you.

But if you're not interested in us, and show it by not following the rules, you get kicked out.

Is this clear enough?

I know it isn't, and it won't be many hours at all before the next illiterate gets the ban.

Would anyone be interested in reading and discussing the book "the theory of open quantum systems" by breuer and petruccione ? Im a master student with focus in solid state physics

So I'm not an expert but in a discussion about time travel this doubt appeared to me and it's killing me, basically my question is if quantum mechanics are truly random would that mean that everytime you travel to the past the next events would be different independently of you interacting with them or not since the mechanics behind them are random?

Sorry for grammar errors I'm not good with english.

I am a junior in high school and I was looking into a career in quantum computing. As far as I have seen, it pays really well (200k+ in my area after a few years), but I was wondering what majors would I need for this? My friends were telling me I would need to have a degree in comp sci along with if I get a masters or PhD in quantum mechanics. Can anyone fact check this?

Hi I'm new here and very interested in quantum mechanics but only really have a slightly deeper than surface level understanding of it. I've never fully understood what counts as a quantum observer and haven't been able to find an answer that I understand online.

The 2 slit experiment had 2 distinct results for when the electrons were being observed and when they weren't, right? So in theory, we could have an objective measure of if a quantum particle is being observed and therefor its waveform is collapsed (1 line or 2 lines showing up on the paper).

The variable in the 2 slit experiment was if the human scientists were in the room looking at it. This is going to be my long list of questions that I haven't found answers for yet:

- What if they closed their eyes?

- What if a camera was pointed at it? If that would count, why doesn't the lines being recorded on the paper where they're hitting count?

- What if they had the results of the waves somehow converted into audio?

- What if they got a child to look at it or someone who otherwise has no idea what they're looking at?

- What if they had a cat watching it?

Theoretically the particles are a binary observed or not observed, so all of these questions should be able to have a yes or no answer.

Edit: I misunderstood the idea of "measurement" before. A person looking at it doesn't affect anything but having equipment set up to monitor which slit the particles traveled through did affect it. That being said, I'm curious where the line is drawn for what kind of equipment would count for properly measuring the data? I know a camera could record it. What if the camera recorded it to a database but didn't immediately display it? What if it recorded to a database but deleted the data immediately after it was logged?

I was reading about FRET/coulombic energy exchange and stubled accross this sentence: " It can be shown that the most important term within the coulombic interaction is the dipole–dipole term, which obeys the same selection rules as the corresponding electric dipole transitions of the two partners (∗A → A and B → ∗B)" (Where A stands for acceptor and B for Donor).

Now I am wondering if "the electric dipole transtion" is the same kind of dipole as in electronic transitions (like for UV-Vis absorption), where the selection rules are the Laport and spin selectino rule, and if they also apply for FRET. Or in general, are there selection rules, like the Laport rule, also for FRET transitions?

Hello everybody , I’m a computational aerodynamicist , and I have been considering starting to learn more about the physics of the very very small , I love aerodynamics, but the fundamental voice in me that wanted to get into STEM was always into particle physics. I am 22 years of age , what would you guys recommend for me as text books to start with ? I am sick about watching endless videos about M-theory , quantum physics, even our reality and I keep circling back to the actual science behind it , I want in !

Just the basics for a good friend who has zero background for any of this.

https://en.m.wikipedia.org/wiki/Delayed-choice_quantum_eraser

I have often heard it said that observation does not influence the outcome of quantum experiments by virtue of consciousness, but rather due to interaction between the observed particle and the measurement instruments in the relevant experiment by collapsing the wave function of the relevant particle. But how does the design of the experimental setup of the delayed choice quantum eraser experiment allow for the wave function of the photons connected to the measurements at D3 and at D4 to collapse purely as a result of measurement instruments rather than conscious observation?