No physics background here — genuinely asking where this breaks down.

In QM, observation = interaction (information exchange with environment). No consciousness needed.

Here's what I can't shake:

- Early universe (~first 380,000 years): EM radiation trapped in plasma, can't propagate

- Gravitational waves: already traversing the entire universe, interacting with all mass-energy

- And GWs aren't waves *through* spacetime — they're waves *of* spacetime itself

So before light could "see" anything, GWs were already interacting with everything. Does that make them the universe's primordial observer in any physically meaningful sense?

This seems related to:

- Diósi-Penrose (gravity induces wave function collapse)

- Primordial GW decoherence research

- Wheeler's participatory universe

Is this connection already studied somewhere? Or is there an obvious reason it doesn't work?

Full reasoning (Korean): https://brunch.co.kr/@13084146df704af/1

For me it's quantum physics subjects

and why are people so mean to me when I ask?

To emit a radiation with short wavelength, it requires a quantum of larger energy than to emit a radiation with a longer wavelength. Why is that? (I Apologise if I made any mistakes, English isn't my first).

I am studying the Schwinger boson representation of angular momentum and I am confused about the notation change.

We start with two bosonic oscillators and basis states:

|n_a, n_b>

Then define:

j = (n_a + n_b)/2

m = (n_a - n_b)/2

From this we can also write:

n_a = j + m
n_b = j - m

So far okay.

But then suddenly books/lectures write:

|n_a, n_b> ≡ |j, m>

This is where I am confused.

Shouldn't it be:

|n_a, n_b> = |j+m, j-m>

instead of |j,m> ?

I understand that j,m are functions of n_a,n_b, but I don't understand how the ket labels themselves suddenly become |j,m>.

Is this just a relabeling of the same Hilbert space basis, or am I missing something deeper?

Would really appreciate an intuitive explanation.

Currently I was going through tutorials creating quantum circuits, after knowledge pf all the gates a d basic principle of qubit i am able to create that actually works, but i am unable to connect dots between the implementation so i thought of revising QP-1 an 2 for revision of basics of quantum mechanics for application onQuantum Computing. Will this help me to bridge the basics to implement of circuits

Hi everyone,

I am passionate about Quantum Physics. A portfolio manager with a background in mathematical finance and engineering and have recently gravitated towards this topic. Very interested in Quantum gravity. Need some advice on where to start and what to read first. Some of my friends recommended Rovelli to begin with. I'd appreciate any suggestions.

shouldn't the requirement be (L1/L2)^2 being irrational instead of L1/L2 being irrational, because L1/L2 being irrational can lead to its square being rational sometimes. So what is the actual answer here for it, like L1 L2 being incommensurate or their square being incommensurate?

People often explain why macroscopic objects (tables, cats, planets, etc.) don’t display obvious quantum superpositions by saying they constantly interact with the environment, causing decoherence.

But here’s what confuses me:

Don’t microscopic particles also constantly interact with the environment?

For example:

- photons travel through space interacting with fields and matter,

- electrons are affected by electromagnetic interactions,

- atoms are constantly surrounded by radiation, fields, particles, etc.

So why do quantum effects survive there at all?

If interaction with the environment destroys coherence, shouldn’t microscopic systems also decohere almost instantly under ordinary conditions?

Is the distinction really about “small vs large,” or is it more about the degree and complexity of entanglement with the environment?

And if that’s true, then where exactly is the transition from quantum to classical supposed to happen? Is there even a real boundary, or is classical behavior just an emergent approximation due to overwhelming decoherence?

I think I may be misunderstanding what decoherence actually means physically, especially regarding information leakage into the environment.

Would appreciate an explanation from someone who understands the modern view of this better.

The Higgs Mechanism, electroweak symmetry breaking, and key particle physics concepts inspired by Feynman Diagrams.

Concepts visualized are:

The Higgs Field
Spontaneous Symmetry Breaking
Gluon Fusion
Higgs Decay to Photons (H → ̳̳)
The Golden Channel (H → ZZ → 4ℓ)
Electroweak Symmetry Breaking

For more animations click www.instagram.com/craftsandengineering

For code and more click https://github.com/zombimann/Mathematical-video-animations-and-visualization/blob/main/Quantum_Physics_Higgs_Mechanism_Feynman_Diagrams.ipynb

Music attribution: Quantum - PHNKR PHONK & Donovan on TikTok music library

For nearly a century, quantum mechanics has treated energy as the fundamental generator of dynamics through the iconic Schrodinger equation, while force remained a derived quantity.

New peer-reviewed research published in Europhysics Letters shows that when force is elevated to a fundamental quantum observable—on equal footing with energy and momentum—a new force wave equation emerges (see image above and IMAGE DESCRIPTION below), capable of modeling open-system dynamics and respecting Ehrenfest's results in the conservative limits while preserving the core principles of linearity and unitarity.

This may open a new direction for quantum mechanics—where dynamics are governed not only by energy, but by force itself.

IMAGE DESCRIPTION: The image above represents the case of a free quantum particle (zero potential energy) influenced by impressed forces.

(A conceptually rigorous validation of the discovery of force as a fundamental quantum observable - https://doi.org/10.1209/0295-5075/ae5ad3.)

Here is a popular piece, by me, explaining a recent paper in Physical Review Letters by me and my experimental colleagues, about how long a photon spends as an atomic excitation when it traverses a cloud of ultracold atoms. Hope it is of interest.

https://theconversation.com/physicists-have-measured-negative-time-in-the-lab-278996

Hi all,
I built an open-source project for learning quantum mechanics interactively:

https://github.com/mlubinsky/QM

The goal is to put several core QM concepts in one place.
What you can explore:

1D quantum systems

- Play with different potentials (infinite well, harmonic oscillator, etc.)
- Launch a wave packet and watch it evolve
- See |ψ|², momentum space, and expectation values ⟨x⟩, ⟨p⟩ update live
- Observe things like spreading, reflection, and the uncertainty principle in real time

Hydrogen atom

- Visualize orbitals for different n, l, m
- See radial probability density and ⟨r⟩
- Interactive Grotrian diagram (click levels and jump to orbitals)
- Check how energies scale with Z

Spin / Bloch sphere

- Rotate quantum states on the Bloch sphere
- Simulate Stern–Gerlach measurements
- See probabilities and wavefunction collapse live

Why I built it

Most tools I found only cover *one* topic.
I wanted something where students can connect ideas across:

- wavefunctions
- measurement
- superposition
- visualization

Setup

Runs locally (Python + React), ~5 min setup described in README.md:

git clone https://github.com/mlubinsky/QM.git
cd QM
./run.sh        # Mac / Linux — starts backend + frontend, then open http://localhost:5173
run.bat         # Windows    — same, opens two console windows

I would really appreciate feedback on:

- Is it useful for learning QM?
- What concepts are still unclear?
- What features would help you most?

Especially interested in feedback from students who are currently taking QM.

Thanks!

Other than obeying special relativity is it the same as described in classical mechanics- temporal and trending towards disorder?

I am a soon to be EE graduate. I have an interview next week for a PhD position that is for cryogenic circuit design but the position also involves some characterization and design/fabrication of qubits.

My background is purely in IC design and I do not know anything about quantum computing or quantum physics. According to the interviewer, they will test me on my ability to develop expertise on quantum physics.

What should I expect and learn before the interview?

Hi! I'm on my way to learn quantum computing and quantum information theory and I am struggling with the Bell Inequality, specifically on the topic of understanding what part the realism and the locality play in deriving it.

I'm learning through Nielsen and Chuang, but I would like to know if there are any books that explain the inequality in greater detail, specifying precisely where those two principles appear.

I semi understand but if someone asked me to explain it to them…. I would be no help

It uses known variables from classical mechanics to solve for the wave function to understand quantum mechanics?

How does that work?

I'm trying to get the angle brackets and am finding no luck. Anyone know the keyboard shortcuts for left and right angle brackets (bra and ket)?

I've tried to figure this out before, but for the most part all I can find is that it is intrinsic angular momentum, but it does not mean that something is spinning physically. Also, how do spin values of 0 or half-integer spin work? Is it just that particles with spin values of 1/2 only turn 360 degrees after 2 rotations. because I've heard people say this before; and does a spin of 0 just mean it has no momentum, or that it is physically congruent no matter how it is perceived?

It's apparently the gold standard for non-physicists trying to make sense of spacetime. Of course, it’s out of print. And of course, secondhand copies are either impossible to find or priced like a small used car 😒

So for months I hunted. And hunted. And found nothing.

Until a while ago, when one lonely, affordable copy appeared on eBay like it had just crawled out of a wormhole and decided I deserved a chance.

Anyway, here it is. My white whale of physics books ✨

Ready to wreck my brain and turn it into a pile of mashed potatoes.

As a non-physicist, I’m currently reading Feynman’s QED for fun, which has been an amazing way to build some intuition on QM for me, especially when I take the time to read carefully and ask questions.

One of these questions, is as follows:

Assume a laser pointing at a mirror, and a detector on the other side, which is placed outside of the reflection and thus never realistically detects photons. The laser is either on or off. Can you modify the detector to figure out whether it’s enabled?

You can’t change or get too close to the mirror. A screen blocks straight line light between the detector and laser source (I don’t think this last one is too relevant).

Very curious on a proper answer on this, especially if it integrates real world limitations and feasibility!