I don’t have a source to hand at the moment, but when I looked into the famous Delayed Choice Quantum Erasure experiment the consensus seemed to be:
- The double slit experiment’s conclusions still hold, but:
- The particularly exciting and stark results of the Quantum Erasure experiment may have been misinterpreted or miscommunicated to the public, in particular:
- The presenter of PBS SpaceTime has said that he regrets certain things about how he worded his video on the Quantum Erasure experiment, and I think may have left a comment on the video to that effect.
Every time I look into QM, I keep coming back to the same fundamental axiom: “Quantum Mechanics’ weirdnesses can make otherwise straightforward things frustrating, but will never make interesting inventions possible.” Like how entanglement is able to break locality (which is frustrating) but without breaking causality (which would be interesting). If you hear about a quantum principle and think “Wow, I could use that to build X,” then it’s more likely that you’re not fully understanding the principle (not “you” specifically, I’ve fallen for this myself countless times).
The only exception seems to be Quantum Computing, but even that only arises out of a deep deep mathematical analysis (you can’t get to QC on your own from the things in popular science books) and is only applicable to really niche applications.
It seems fairly obvious that the universe avoids doing work when it’s not necessary. I agree we’ll probably be disappointed looking for magical ways to make it yield much more.
> The only exception seems to be Quantum Computing
Yet so far it failed to do any useful work, correct? As I understand it, even the recent "quantum supremacy" results were about performing a humongous number of useless computations.
It would be funny if this turned out to also apply to quantum computing. Ie while we can build a quantum computer, we can't actually find any productive problem that calculates faster than a classical algorithm.
QC would turn out to be the biggest bust in physics (after string theory of course).
So far yes, but we should be able to in principle for a few kinds of problems.
Entanglement doesn't violate locality, it's measurement that does that. And that's because we don't have a rigourous handle on what measurement actually is, and why we call it "the measurement problem"!
Didn't they originally use polarizing filters to measure photonic phase?
If it were possible to measure the phase of a photon after a beam splitter in a nondestructive way, shouldn't it be possible to determine whether measuring one causes state collapse in the other?
This says that photonic entanglement is polarization, and that photonic phase can be inferred from second order of intensity, IIUC:
"Bridging coherence optics and classical mechanics: A generic light polarization-entanglement complementary relation" (2023) https://journals.aps.org/prresearch/abstract/10.1103/PhysRev...
Shouldn't it then be possible to nondestructively measure photons and thus entanglement?
> If it were possible to measure the phase of a photon after a beam splitter in a nondestructive way
"Non-destructive measurement" is an oxymoron. It's not a real measurement if it doesn't destroy the coherence of entanglement. Weak measurements do destroy some entanglement, just not "all" of it.
So you don't think a laser is an interesting invention? Those require quantum mechanics for the stimulated emission.
Quantum tunneling is key to many devices as well.
Then of course there's the reality that the mere existence of everything we see around us - the stability of atoms themselves - requires quantum mechanics.
Quantum Enxryption!
>about a quantum principle and think “Wow, I could use that to build X,”
We use quantum principles to build things all the time. What are you talking about?
https://en.wikipedia.org/wiki/Quantum_sensor#Research_and_ap... is just a few examples.
I’m talking about building sexy things like ansibles or FTL engines. The kinds of transcendent ambitions that Quantum Mechanics often inspire in laypeople like me.
Every device one has that has integrated circuits (chips) and some of the discrete components was designed based on the quantum mechanical properties of materials that were beyond us until we understood quantum mechanics - sometimes we get too accustomed to the wonder right in front of us. The Electrical Engineering curriculum at my university started with Quantum Electrodynamics for a semester. Figuring out how the sun and stars work required an understanding of the smallest particles, it's all kind of amazing.
I don’t think it was intended to say that quantum effects are never useful.
I interpreted the comment to mean that at at first glance quantum effects get things like instantaneous, FTL communications… but those most dramatic possibilities never work out when you dig deeper.
Let me put it this way: my axiom is aimed at people (like me) who read popular science books, skim the textbooks, and think there might be a way to make a time machine or if not that then “at least something interesting” of a similar nature.
If you have a graduate degree in quantum mechanics or work for Intel as a designer/engineer of microprocessors then yeah, you can consider yourself exempt.
I read this after someone recommended it here, you may enjoy it: https://www.penguinrandomhouse.com/books/612737/how-to-make-...
The title is inspired by that Carl Sagan quote from Cosmos, and the science is understandable for the most part by laypeople. There are science parts towards the end that I had to read a couple of times because it's just so unintuitive.
Even if we had a "stranglehold" on the deepest foundations of Quantum Mechanics it wouldn't help you with either of those things. In order for those things we need something beyond QM and a lot more grand. FTL travel and communication is in the ball park of relativity.
QM is not an umbrella term for sci-fi.
Night vision goggles use quantum mechanics. Pretty sexy.