8 ms·
Scientists simulate backward time travel using quantum entanglement
- andreareina 3y agoPaper: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.131.150202 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 simulations to pinpoint a counterintuitive nonclassical advantage achievable with entanglement. Our experiment echoes a common information-processing task: A metrologist must prepare probes to input into an unknown quantum interaction. The goal is to infer as much information per probe as possible. If the input is optimal, the information gained per probe can exceed any value achievable classically. The problem is that, only after the interaction does the metrologist learn which input would have been optimal. The metrologist can attempt to change the input by effectively teleporting the optimal input back in time, via entanglement manipulation. The effective time travel sometimes fails but ensures that, summed over trials, the metrologist’s winnings are positive. Our Gedankenexperiment demonstrates that entanglement can generate operational advantages forbidden in classical chronology-respecting theories.
- pama 3y agoThere is a nice explanation at the end of the letter: “While PCTC simulations do not allow you to go back and alter your past, they do allow you to create a better tomorrow by fixing yesterday’s problems today.”
- DaveSchmindel 3y agoInteresting. Isn't that just problem solving? If yesterday's problems are unsolved by today, aren't they just today's problems?
- gerad 3y agoI read it as: - Today, I need to predict tomorrow’s weather. - Yesterday I made some measurements of the (temperature, pressure, etc) conditions that I need for today’s prediction. - Yesterday it was impossible to know what measurements I’d optimally need to take for today’s forecast. - Today, I can (quantumly, probabilisticly) go back in time and make sure I have the optimal set of measurements for today’s prediction. - I can’t change anything that happened between yesterday and today, but I now have better information I can use to change tomorrow.
- goodluckchuck 3y agoSo you can measure the past, but not change it?
- xwdv 3y agoIf you already know the optimal set of measurements why not skip the whole traveling back in time part and just change tomorrow today?
- gerad 3y ago> The problem is that, only after the interaction does the metrologist learn which input would have been optimal.
- dvaletin 3y agoBasically, having infinite budget you can send any gift you can imagine to your friend via Amazon at day-1 and cancel irrelevant orders at day-0 except correct one to make your friend happy at his BD, which is day+1. Make better future correcting your past decisions based on today information. Now the question is: how to get enough money?
- chrisweekly 3y ago"Our Gedankenexperiment demonstrates that..." "Gedankenexperiment" sounds an awful lot like "thought experiment".
- kadoban 3y agoThat's the translation, yeah. They're a very important tool in physics for exploring the consequences of known or hypothsized physical principles.
- mdekkers 3y agoThat’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.
- galaxyLogic 3y agoI 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.
- dr_kiszonka 3y agoA less charitable interpretation would be that is a form of self-aggrandizement.
- MrRolleyes 3y ago[dead]
- Guvante 3y agoLayperson's read but the paper seems to say "this is weird we were accurate than should be possible" combined with "causal order wouldn't make sense here" Much less "we found time travel" and more "that was weird maybe it was time travel". Also note that to my knowledge there is no form of talking about entanglement that involves time before entanglement or any meaningful manipulation of the entangled particle. Thus even if you could talk backwards in time with entangled particle it is unlikely to make a meaningful difference at distances measured less than how far light travels in that time.
- halfcat 3y ago> 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 conclusion was, it would be possible theoretically, but you wouldn’t be able to read the result. The sci-fi enjoyer part of me likes to believe CERN is a big delayed choice quantum eraser experiment used to receive messages from the future.
- elcritch 3y agoI'm reading (well listening to) a sci-fi novel based on that premise called "Quantum Radio". Pretty classic techno-thriller, complete with shadowy organizations. I really enjoyed the premise and setup of CERN data being used as a quantum radio reading messages from the future, or perhaps parallel universes.
- pmontra 3y agoThis one? [1] Beware, it's a review so there are possible spoilers. [1] https://sfbook.com/quantum-radio.htm https://sfbook.com/quantum-radio.htm
- 3y ago
- fullarr 3y agoI simulate backward time travel all the time It's called my imagination...
- wizardforhire 3y agoYah 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?…
- I_Am_Nous 3y agoI mean, not lately
- jrflowers 3y agoAnyone can do that in their imagination
- doublerabbit 3y agoYep. They're called drugs.
- amelius 3y agoI simulate backward time travel simply by putting the objects around me back into the state they were in some time ago.
- thunkle 3y agoWow these ads are intrusive. I just got done listening to Penrose talking about this. Interesting timing.
- pmontra 3y agoSo all those blank spots in the page are ads? uBlock Origin and NoScript, thank you!
- iosystem 3y agoI suppose the actual paper is describing retrocausality and not time travel but maybe I'm perceiving that wrong?
- westurner 3y ago"Scientists spot the telltale tick of a time crystal in a kid's toy" (2018) https://newatlas.com/time-crystal-found-crystal-growing-kit/54469/ https://newatlas.com/time-crystal-found-crystal-growing-kit/... Time Crystal: https://en.wikipedia.org/wiki/Time_crystal https://en.wikipedia.org/wiki/Time_crystal /q discrete time crystal "retrocausality" https://www.google.com/search?q=discrete+time+crystal+%22retrocausality%22 https://www.google.com/search?q=discrete+time+crystal+%22ret... Delayed choice quantum eraser: https://en.wikipedia.org/wiki/Delayed-choice_quantum_eraser https://en.wikipedia.org/wiki/Delayed-choice_quantum_eraser From https://news.ycombinator.com/item?id=28402527 https://news.ycombinator.com/item?id=28402527 : > one must perform electrodynamic engineering in the time domain, not in the 3-space EM energy density domain. And from https://news.ycombinator.com/item?id=35877402#35886041 https://news.ycombinator.com/item?id=35877402#35886041 : > Physical observation (via the transverse photon interaction) is the process given by applying the operator ∂/∂t to (L^3)t, yielding an L3 output ... > FWIU electrons are most appropriately modeled with Minkowski 4-space in the time-domain; (L^3)t Retrocausality > Physics: https://en.wikipedia.org/wiki/Retrocausality#Physics https://en.wikipedia.org/wiki/Retrocausality#Physics
- AIorNot 3y agoThe letter discusses a theoretical framework to understand certain quantum phenomena, which includes simulating hypothetical constructs known as Closed Timelike Curves (CTCs). CTCs in the realm of general relativity are paths through spacetime that, if they could exist, would allow for time loops and, in that sense, "time travel." However, in this letter, CTCs are not being used to propose actual time travel, but are rather a conceptual tool to explore certain quantum behaviors. In the scenario outlined in the paper, the authors simulate CTCs using quantum-teleportation circuits to explore how information can be "sent" back in time, effectively. In other words, they explore a situation where information from the future could be used to amend the state of a quantum system in the past to achieve a metrological advantage. They employ quantum entanglement and post-selection to simulate a scenario where a certain state in a quantum metrology experiment can be determined based on future information, which is then effectively sent back to amend the initial state of the system. The key takeaway is that the authors are not suggesting actual time travel, but are employing the notion of CTCs and quantum simulation to delve into a complex theoretical exploration of quantum metrology. This exploration reveals how entanglement can simulate what would be effects of retrocausality, meaning effects that appear to violate the typical forward flow of cause and effect, to achieve certain advantages in metrology, which is the science of measurement. From GPT In essence, this is a very high-level theoretical discussion that uses the concept of time travel as a tool to explore certain quantum phenomena, rather than a proposal or explanation of practical time travel.
- soperj 3y agoIf you can pass a message from the future, you could pretty easily game the stock market no? Even if it's just an equation you could pick a volatile stock and just send a + result or a negative result and that would determine whether you bought or shorted.
- __turbobrew__ 3y agoSomething 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 curious what in quantum mechanics is considered “canon” vs purely hypothetical ideas.
- halfcat 3y ago> what in quantum mechanics is considered “canon” vs purely hypothetical ideas Yes. And no.
- nyssos 3y ago> 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.
- deleted 3y ago[deleted]
- spoonfeeder006 3y agoIs 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?
- nyssos 3y agoIt's just entanglement.
- deleted 3y ago[deleted]
- deleted 3y ago[deleted]
- zubairq 3y agoHow similar is this technique to Ronald Mallett's time travel device? https://en.wikipedia.org/wiki/Ronald_Mallett https://en.wikipedia.org/wiki/Ronald_Mallett
- ben_w 3y agoNot very. Mallet's is based on relativity while this is based on quantum mechanics, and at the moment we don't even have a good way to combine the two models of reality. Also, Mallet's would (if it worked) send stuff back in time, whereas this (if I read it right which is a big if) would make a genuinely random choice now just happen to be slightly correlated with the correct answer to the question you're about to ask.
- galaxyLogic 3y ago(a cartoon on the web somewhere:) What do we want? Time-Travel! When do we want it? Doesn't matter!
- vt_mruhlin 3y ago> create a better tomorrow by fixing yesterday’s problems today This is exactly the kind of tag line an evil corporation in a sci-fi movie would brand this product with.