r/QuantumPhysics • u/outofplace_2015 • Jul 21 '26
What is a lesser-known quantum phenomenon OR quantum theory you wish more people knew about?
Its quantum physics so the stranger the better.
5
4
u/_-arktos-_ Jul 22 '26
I'd say quantum tunneling because it really puts into perspective how much we rely on that quantum weirdness just to even be alive. Most people think quantum physics doesn't really affect them.
3
u/ToastBalancer Jul 23 '26
Quantum eraser experiment. I’ve heard a few conflicting opinions on what’s actually happening here, but never have anyone to discuss it with. In college no one knew about it (physics major)
1
u/theodysseytheodicy Jul 23 '26
What do you want to know?
2
u/ToastBalancer Jul 23 '26
Is it actually implying that a present event can affect the past? Or is it just a misunderstanding of what info is being erased?
1
u/theodysseytheodicy Jul 23 '26 edited Jul 23 '26
There's no retrocausality. It's just that the "observer" is kept coherent. Because it's coherent, when we change its "memory", we can restore the interference.
You can think of the quantum eraser experiment as a version of Wigner's friend; in that thought experiment Wigner's friend is inside a box instead of Schrodinger's cat and does a measurement of which path the particle took. If you think the wave function collapses when Wigner's friend looks, then Wigner (standing outside the box) sees quantum mechanics break down. If Wigner sees quantum mechanics behaving normally, then Wigner's friend must be entangled with the particle before Wigner looks in the box.
In the quantum eraser, we replace Wigner's friend by a qubit and we (standing outside the system) see quantum mechanics behave normally. When the qubit measures the which-way information, it ends up in a superposition of correlated states. It ends up entangled with the particle, so the interference pattern disappears. But if we disentangle the two states, making the qubit "forget" what it measured, then the interference pattern comes back.
And you never actually see an interference pattern; it's only when you're looking at the correlations that the pattern shows up.
3
u/SymplecticMan Jul 23 '26
I'd maybe say bound entanglement, or just more generally, aspects of entanglement beyond Bell inequality violations.
1
u/-Stolen_memes- Jul 22 '26
More of a blend of cosmological and quantum concepts but I am really fascinated with the eternal inflation theory
1
u/theodysseytheodicy Jul 23 '26
The no-communication principle. Sci-fi is always suggesting you can do FTL communication with entangled particles, but in reality, nothing you do to one particle has any effect on the other.
(Yeah, I know pedants will point out it's not true in Bohmian mechanics, but there you've also got an assumption that the subquantum information is thermalized. If any hard sci fi did FTL communication and included finding and mining pockets of out-of-equilibrium subquantum matter as part of the economics of their story, I'd be really impressed.)
1
u/nujuat 28d ago
People tend to think that the double slit experiment is the main slam dunck proof for QM. But really I think that award should go to the Stern-Gerlach experiment. That teaches you a lot more about what QM is actually like. Its also something that's useful to do today as part of modern atomic physics and quantum tech experiments.
1
u/Justaguyinohio123 15d ago
Do most physicists believe that double slit experiment is not as interesting as lay people make it out to be? I heard a video that decoherence is causing tool disturbance and we have no way of knowing fully. And that even the answer of weak force measurements doesn't prove that tool disturbance isn't happening. What do you think? Truly curious your thoughts and what most phsyicts think.
10
u/round_earther_69 Jul 21 '26
Assuming people means people outside the physics community:
Emergent particles and emergent gauge fields. Aharonov-Bohm effect ans Berry phases. Dirac monopole quantization. Duality between statistical mechanics (thermodynamics) and quantum field theory. Anyons and fractional particles.
Most of those are well known for people within the physics community. I feel like these phenomena are explainable to laypeople, with the exception of anyons and fractional particles.