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Time Warp: Delayed-choice quantum erasure

drgblackwell.substack.com

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Re: Time Warp: Delayed-choice quantum erasure

#51

Earlier quoted context omitted.

They do. In fact i always thought this was the answer to the matter/antimatter imbalance. Feynmann diagrams literally show anti matter as the same particle as a matter particle, just travelling back in time (see election/positron interactions). So what happens when matter and antimatter are created in a big boom? Well the antimatter is in the past, we're here in the future.

Not sure how we could ever prove something like that but it's certainly an amusing and symmetrical view of the universe: big bangs create two universes, moving in opposite time directions from each other. Each seeing the other's particles as anti-particles. Thinking about it though: photos are their own antiparticle. So I'd expect to see a lot more cosmic microwave background than we should because at least in the ea…

I'm not at all invested in the above except as a vague thought experiment but imho...

No theory can match CMB as well as the current theories that add cosmic inflation on an as needed basis in time and space to make CMB observations match perfectly. But cosmic inflation is a completely unknown mechanism (no explanation at the level of particle physics) and it was added specifically to make CMB match perfectly. In some ways i think the current 'we observe CMB to be this so we'll move these free variables to make it match' make CMB non-falsifiable. You could add similar free variables to any theory to make CMB match.

Re: Time Warp: Delayed-choice quantum erasure

#52
I did some actual research in making a delayed choice quantum erasure system and the TLDR of why any of these "time travel" results is that what you have to keep in mind is that it is that the entanglement you create you have to still use a classical channel of information to transmit the information as a result which is still bound the speed of light which is what the quantum erasure systems must also show that it doesn't occur.

Re: Time Warp: Delayed-choice quantum erasure

#53
post #40

Quantum physicist here. My PhD back in the day was about the entanglement between downconverted photons. I've thought about this more than I like to admit. While I appreciate the blog post, it seems a bit disingenuous. I hope everyone understand that if you take two entangled photons A and B and detect A before B, then the outcome of the measurement of B must depend on the outcome of the earlier measurement of A, bec…

> I hope everyone understand that if you take two entangled photons A and B and detect A before B, then the outcome of the measurement of B must depend on the outcome of the earlier measurement of A, because measuring A causes the collapse of the joint state and determines the wavefunction of B undergoing the later measurement. This bakes in an assumption that collapse happens, which I don't believe everyone agrees w…

Sure sure, you can ignore that wording. The point is that the first measurement determines the state of the particle undergoing the second measurement.

Re: Time Warp: Delayed-choice quantum erasure

#55
post #29

Earlier quoted context omitted.

Theoretically you'd just need an enormous telescope to collect enough light to resolve an image. Though based on the features that modern telescopes can resolve on the moon ~1 light second away, it'd probably need a telescope on the scale of a galaxy

At some point there might be it be enough photons, though, right?

Nope! We can detect individual photons (and measure their properties) and a mirror can (nearly) perfectly focus and collect every photon that hits it. The frequency of detection events would change with the distance, but the frequency doesn't hugely matter, one photon per week is enough for science!

Re: Time Warp: Delayed-choice quantum erasure

#56
post #40

Quantum physicist here. My PhD back in the day was about the entanglement between downconverted photons. I've thought about this more than I like to admit. While I appreciate the blog post, it seems a bit disingenuous. I hope everyone understand that if you take two entangled photons A and B and detect A before B, then the outcome of the measurement of B must depend on the outcome of the earlier measurement of A, bec…

The delayed choice experiment doesn't contain a bell inequality, so spacelike seperation doesn't really mean much here. You can reproduce the results with local classical models.

Re: Time Warp: Delayed-choice quantum erasure

#57
post #40

Quantum physicist here. My PhD back in the day was about the entanglement between downconverted photons. I've thought about this more than I like to admit. While I appreciate the blog post, it seems a bit disingenuous. I hope everyone understand that if you take two entangled photons A and B and detect A before B, then the outcome of the measurement of B must depend on the outcome of the earlier measurement of A, bec…

The author talks about "two downconverted photons" each at half the energy, in that simple linear experiment. Is that mainstream physics? If so ... big ask, but do you happen to have a butt-simple reference at the undergrad QM level? It feels like I need more equipment than a fixed pair of slits to downconvert frequencies.

Re: Time Warp: Delayed-choice quantum erasure

#58
post #35

I literally posted about this topic a few days ago! But for some reason it was flagged as a “Dupe” and buried by someone: https://news.ycombinator.com/item?id=43173195 It links here: https://chatgpt.com/share/67bde29f-a56c-800a-8e26-44a5a3ad23... I will summarize by saying that I think our current understanding of Faster-than-Light communication is wrong, and the no-go theorem about no information transmission faster…

I'm sorry but the chat format is a really poor way to share ideas. It's long, meandering, and contains many instances of wrong and not-even-wrong assertions by you (expected, you don't claim to be an expert, but hurts your credibility) and by chatGPT (expected, hallucinations, but makes it impossible to believe any assertion without already knowing what makes sense). If you believe you came up with something worth sh…

You're totally right that I am not a scientific expert on this by any means. But often, breakthroughs in science come not from orthodoxy or experts, but exactly the people who don't believe in the orthodoxy. https://en.wikipedia.org/wiki/Planck%27s_principle

Examples include:

Einstein's theory of relativity vs luminferous ether orthodoxy

Rutherford's discovery of radioactivity vs the 100 million age of the earth orthodoxy following Lord Kelvin, Feynman noted how scientists kept staying within a certain range until the next generation suddenly felt bold enough to go further https://www.americanscientist.org/article/kelvin-perry-and-t...

Pasteur's discovery of microbes against the orthodoxy that continually ridiculed people like Ignaz Semmelweiss even decades later https://en.wikipedia.org/wiki/Ignaz_Semmelweis ... people still believed in spontaneous generation of living matter

Galileo's insistence on the heliocentric model, etc. https://www.history.com/this-day-in-history/galileo-is-accus...

Ancient greek ideas of phlogiston, the four humours, etc. or the idea that the heart rather than the brain is where thoughts originate, were in place for millennia

So, engage me on the substance. Discuss the actual substance of what I said. I am saying that PWT explains what we observe in quantum mechanics, and preserves realism at the expense of locality. And that FTL communication is not just possible but a lot less weird than Everett's MWI. I am saying that even if we can escape the light cone that doesn't mean necessarily that we can send information back in time (the ways postulated involve a lot of assumptions) and even if we did, it wouldn't violate any major principles.

I'm saying that we have to use classical mechanics to move the entangled parties apart. So we can't escape our existing light cone, or send messages to the past. But going forward, once we do set it up, we can build e.g. security systems that can't be stopped because they "teleport" some information to another location, even if wires are cut and electrical signals are blocked. I'm saying you don't need to classically move things in order to teleport information.

Einstein's objections that you can send information back in time involve exotic constructs and massive assumptions. And even if they were true, this wouldn't cause any paradoxes. Because the effect is tiny, and the probability of it being amplified is tiny, same as the probability of you passing through a wall due to quantum fluctuations.

But, the way it would manifest is that measurements would be probabilistically biased one way or the other. If there is an intelligence on the other side, it can actually act on this information. This FTL doesn't mean sending info back in time. But even if we were able to, then eventually with enough bandwidth we could communicate with the past, through this thing. It would be like a magic 8-ball that tells you some things. With enough bandwidth you might be able to bootstrap a stronger solution, ending up with a Closed Timelike Curve. I'm saying that there are still no paradoxes at that point because if you can believe Everett's MWI of worlds forking all the time everywhere, then you can certainly believe that worlds fork in these extremely rare scenarios of a closed timelike curve. So you have a sort of corkscrew where in some worlds you bootstrapped the thing, and in other world a lot of information is arriving from the future. But all that is very theoretical and not required just for FTL communication.

The way we achieve FTL communication is to improve quantum error-correction, as Microsoft has done. Once we have enough qubits, it may turn out that the randomness was because we are just "were not able to throw the dice in a controlled enough manner". That's what the DeBroglie-Bohm's Pilot Wave Theory says. It postulates local realism (attributing the randomness to our limitations), and accepts FTL information transmission via pilot waves. And by the way the other, wackier, theories don't rule out FTL communication either.

So we will soon enter an era where we can test this. When we overcome the quantum error rates and prevent decoherence, we'll be able to actually INFLUENCE remote measurements at FTL speeds. Not perfectly, but enough that we can send information. That's my prediction. Then we'll know if PWT is actually true.

This idea that all interpretations of quantum theory are exactly the same, in that they produce exactly the same predictions, is only true while the randomness and error rate is high. Once we learn to cancel out the errors, suddenly we'll get a "clearer picture" and be able to throw the dice more accurately.

Re: Time Warp: Delayed-choice quantum erasure

#59

Earlier quoted context omitted.

At some point there might be it be enough photons, though, right?

Nope! We can detect individual photons (and measure their properties) and a mirror can (nearly) perfectly focus and collect every photon that hits it. The frequency of detection events would change with the distance, but the frequency doesn't hugely matter, one photon per week is enough for science!

It is definitely possible that I’m missing something here.

But, for example, if we are trying to get an image of a dinosaur, and we’re only getting one photon per week, how’s that work? The dinosaur should have moved before the second photon is sent off, right?

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