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Scientists simulate backward time travel using quantum entanglement

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Re: Scientists simulate backward time travel using quantum entanglement

#31

Post by nyssos »

dheerajvs wrote: post #23
halfcat wrote: post #19

Earlier quoted context omitted.

> unlikely to make a meaningful difference at distances measured less than how far light travels in that time PBS Space Time did an episode that posed the question as a delayed choice quantum eraser experiment where the “long” leg is farther away, like on the moon, and we somehow reflect a particle back and forth to delay the observation indefinitely. I also wonder if they can do something like this at CERN. Their co…

Hasn't the supposed weirdness of the delayed choice quantum eraser experiment been debunked? Can someone in the field please confirm? I find contradictory videos on YouTube.

Depends on what you mean by "weirdness". Whether you see interference really does depend on which axis you choose to measure along, but it's not because you're sending signals backwards in time. The electron was in a superposition of interfering and not interfering all along: the delayed choice is just choosing which component of that superposed state you want to measure.

Re: Scientists simulate backward time travel using quantum entanglement

#32

Post by dr_kiszonka »

galaxyLogic wrote: post #29
mdekkers wrote: post #25

Earlier quoted context omitted.

That’s literally what it means, and it’s a minor nitpick I have - it’s an English paper, just use English. Using the German word here just increases noise.

I think it comes from Einstein whose Gedanken Experiments lead to the discovery of relativity. Einstein came from a German-speaking country. So what the authors are saying is "We're basically doing a similar thing as Einstein did". Jargon is to be avoided but this is more like a tribute to the great physicist Einstein.

A less charitable interpretation would be that is a form of self-aggrandizement.

Re: Scientists simulate backward time travel using quantum entanglement

#33

Post by nyssos »

tobiasSoftware wrote: post #24
halfcat wrote: post #19

Earlier quoted context omitted.

> unlikely to make a meaningful difference at distances measured less than how far light travels in that time PBS Space Time did an episode that posed the question as a delayed choice quantum eraser experiment where the “long” leg is farther away, like on the moon, and we somehow reflect a particle back and forth to delay the observation indefinitely. I also wonder if they can do something like this at CERN. Their co…

The delayed choice quantum eraser is misunderstood (even by PBS Spacetime) to invoke time travel/retrocausality. The truth is that the pattern seen on the screen is the same whichever set of detectors you send it to, and as such, there is no evidence of time travel. The more plausible explanation behind the delayed choice quantum eraser involves Heisenberg's Uncertainty Principle, which states that you cannot obtain…

> The more plausible explanation behind the delayed choice quantum eraser involves Heisenberg's Uncertainty Principle, which states that you cannot obtain position and momentum to a high degree of accuracy at the same time.

This is not what's going on: uncertainty principles are a generic feature of wave mechanics, quantum or classical. Delayed choice quantum eraser experiments are just an ordinary case of entanglement.

> I am writing a book on Quantum Physics and have spent months doing research and finding out that even many quantum physics Youtubers routinely say misinformation.

I strongly suggest you work through a quantum physics textbook first. Griffiths is a standard choice: the interpretational aspects leave a lot to be desired, but that's unfortunately unavoidable in introductory texts. You're right that physics youtubers have no idea what they're talking about - but frankly if that surprises you then you're really not ready to filter out the garbage on your own.

Re: Scientists simulate backward time travel using quantum entanglement

#34

Post by 77pt77 »

dr_kiszonka wrote: post #32
galaxyLogic wrote: post #29

Earlier quoted context omitted.

I think it comes from Einstein whose Gedanken Experiments lead to the discovery of relativity. Einstein came from a German-speaking country. So what the authors are saying is "We're basically doing a similar thing as Einstein did". Jargon is to be avoided but this is more like a tribute to the great physicist Einstein.

A less charitable interpretation would be that is a form of self-aggrandizement.

It's both.

Re: Scientists simulate backward time travel using quantum entanglement

#35

Post by nyssos »

__turbobrew__ wrote: post #13

Something I wonder is where is the line in quantum physics where there is no experimental evidence? Obviously things like wave-particle duality have been rigorously experimentally proven, but you hear things about quantum fields, virtual particles, quantum gravity, and others and to a layperson like my self it seems like there is much less — maybe even no — experimental evidence for some of these theories. I’m always…

> but you hear things about quantum fields

Fields are not exotic objects at all: they're just assignments of some quantity (a number, a vector, a linear transformation, something more complicated) to each point in some space. Take the elevation of every point on the Earth's surface, for instance: that's a field. Wind velocity is a field. The stresses inside some solid material are a field. They're absolutely foundational to physics.

> virtual particles

Virtual particles are a mnemonic device for approximating certain very complicated integrals, they don't actually exist.

> quantum gravity

Quantum gravity is a topic, not (yet) a particular thing. We have an extremely good theory of gravity (general relativity), and an extremely good theory of most of the rest of physics (the Standard Model, and more generally quantum field theory) - and they're impossible to reconcile with each other. So despite their empirical success, we know for a fact that both are false. What we want is a single consistent theory that incorporates both fundamental particle physics and gravity: a theory of quantum gravity. And while we know roughly what sort of experiments would allow us to investigate it directly, they would require particle colliders larger than the Earth to carry out. So for the moment all the theorists can really do is investigate candidate theories in preparation for the day when someone (hopefully) figures out an easier way to test them.

> what in quantum mechanics is considered “canon”

All of the formalism, very little of the interpretation.

Re: Scientists simulate backward time travel using quantum entanglement

#36

Post by nyssos »

spoonfeeder006 wrote: post #18

Is this actually simulating backward time travel? Or is it just doing entanglement? I.e. somehow entangling the state of your "gift" on day 1 with the message you receive later so that when you get the message it collapses the state of the gift to the right one?

It's just entanglement.

Re: Scientists simulate backward time travel using quantum entanglement

#37

Post by euroderf »

dr_kiszonka wrote: post #32
galaxyLogic wrote: post #29

Earlier quoted context omitted.

I think it comes from Einstein whose Gedanken Experiments lead to the discovery of relativity. Einstein came from a German-speaking country. So what the authors are saying is "We're basically doing a similar thing as Einstein did". Jargon is to be avoided but this is more like a tribute to the great physicist Einstein.

A less charitable interpretation would be that is a form of self-aggrandizement.

Sort of like wrapping yourself in the flag.

Of Einstein.

Re: Scientists simulate backward time travel using quantum entanglement

#38

Post by forgotusername6 »

chrisweekly wrote: post #17
andreareina wrote: post #2

Paper: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.13... > We construct a metrology experiment in which the metrologist can sometimes amend the input state by simulating a closed timelike curve, a worldline that travels backward in time. The existence of closed timelike curves is hypothetical. Nevertheless, they can be simulated probabilistically by quantum-teleportation circuits. We leverage such simul…

"Our Gedankenexperiment demonstrates that..." "Gedankenexperiment" sounds an awful lot like "thought experiment".

This has just unlocked a childhood memory of mine. I read a book as a young child about a girl and her grandfather who did experiments about space and time. The girl's name was Gedanken. It explored some of Einstein's theories in the form of short adventures. I've been struggling to find the name of the book. Does anyone else remember this book?

Re: Scientists simulate backward time travel using quantum entanglement

#39

Post by fodkodrasz »

chrisweekly wrote: post #17
andreareina wrote: post #2

Paper: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.13... > We construct a metrology experiment in which the metrologist can sometimes amend the input state by simulating a closed timelike curve, a worldline that travels backward in time. The existence of closed timelike curves is hypothetical. Nevertheless, they can be simulated probabilistically by quantum-teleportation circuits. We leverage such simul…

"Our Gedankenexperiment demonstrates that..." "Gedankenexperiment" sounds an awful lot like "thought experiment".

With the main difference that it sound way cooler.

Re: Scientists simulate backward time travel using quantum entanglement

#40

Post by doublerabbit »

wizardforhire wrote: post #5
fullarr wrote: post #4

I simulate backward time travel all the time It's called my imagination...

Yah but have you set up a set of statically significant entangled bosons in a Hau array and then coupled those to your cerebral cortex to be able to meaningfully act upon the knowledge gained by said imagination?…

Yep. They're called drugs.
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