Physicists Reverse Time Using Quantum Computer (phys.org) 95
fahrbot-bot shares a report from Phys.Org: Researchers from the Moscow Institute of Physics and Technology teamed up with colleagues from the U.S. and Switzerland and returned the state of a quantum computer a fraction of a second into the past. They also calculated the probability that an electron in empty interstellar space will spontaneously travel back into its recent past. The study is published in Scientific Reports.
Quantum physicists from MIPT decided to check if time could spontaneously reverse itself at least for an individual particle and for a tiny fraction of a second. That is, instead of colliding billiard balls, they examined a solitary electron in empty interstellar space. "Suppose the electron is localized when we begin observing it. This means that we're pretty sure about its position in space. The laws of quantum mechanics prevent us from knowing it with absolute precision, but we can outline a small region where the electron is localized," says study co-author Andrey Lebedev from MIPT and ETH Zurich. The physicist explains that the evolution of the electron state is governed by Schrodinger's equation. Although it makes no distinction between the future and the past, the region of space containing the electron will spread out very quickly. That is, the system tends to become more chaotic. The uncertainty of the electron's position is growing. This is analogous to the increasing disorder in a large-scale system -- such as a billiard table -- due to the second law of thermodynamics.
"However, Schrodinger's equation is reversible," adds Valerii Vinokur, a co-author of the paper, from the Argonne National Laboratory, U.S. "Mathematically, it means that under a certain transformation called complex conjugation, the equation will describe a 'smeared' electron localizing back into a small region of space over the same time period." Although this phenomenon is not observed in nature, it could theoretically happen due to a random fluctuation in the cosmic microwave background permeating the universe. The team set out to calculate the probability to observe an electron "smeared out" over a fraction of a second spontaneously localizing into its recent past. It turned out that even across the entire lifetime of the universe -- 13.7 billion years -- observing 10 billion freshly localized electrons every second, the reverse evolution of the particle's state would only happen once. And even then, the electron would travel no more than a mere one ten-billionth of a second into the past. The researchers then attempted to reverse time in a four-stage experiment by observing the state of a quantum computer made of superconducting qubits, instead of an electron. The researchers "found that in 85 percent of the cases, the two-qubit quantum computer returned back into the initial state," reports Phys.Org. "When three qubits were involved, more errors happened, resulting in a roughly 50 percent success rate. According to the authors, these errors are due to imperfections in the actual quantum computer. As more sophisticated devices are designed, the error rate is expected to drop."
Quantum physicists from MIPT decided to check if time could spontaneously reverse itself at least for an individual particle and for a tiny fraction of a second. That is, instead of colliding billiard balls, they examined a solitary electron in empty interstellar space. "Suppose the electron is localized when we begin observing it. This means that we're pretty sure about its position in space. The laws of quantum mechanics prevent us from knowing it with absolute precision, but we can outline a small region where the electron is localized," says study co-author Andrey Lebedev from MIPT and ETH Zurich. The physicist explains that the evolution of the electron state is governed by Schrodinger's equation. Although it makes no distinction between the future and the past, the region of space containing the electron will spread out very quickly. That is, the system tends to become more chaotic. The uncertainty of the electron's position is growing. This is analogous to the increasing disorder in a large-scale system -- such as a billiard table -- due to the second law of thermodynamics.
"However, Schrodinger's equation is reversible," adds Valerii Vinokur, a co-author of the paper, from the Argonne National Laboratory, U.S. "Mathematically, it means that under a certain transformation called complex conjugation, the equation will describe a 'smeared' electron localizing back into a small region of space over the same time period." Although this phenomenon is not observed in nature, it could theoretically happen due to a random fluctuation in the cosmic microwave background permeating the universe. The team set out to calculate the probability to observe an electron "smeared out" over a fraction of a second spontaneously localizing into its recent past. It turned out that even across the entire lifetime of the universe -- 13.7 billion years -- observing 10 billion freshly localized electrons every second, the reverse evolution of the particle's state would only happen once. And even then, the electron would travel no more than a mere one ten-billionth of a second into the past. The researchers then attempted to reverse time in a four-stage experiment by observing the state of a quantum computer made of superconducting qubits, instead of an electron. The researchers "found that in 85 percent of the cases, the two-qubit quantum computer returned back into the initial state," reports Phys.Org. "When three qubits were involved, more errors happened, resulting in a roughly 50 percent success rate. According to the authors, these errors are due to imperfections in the actual quantum computer. As more sophisticated devices are designed, the error rate is expected to drop."
Trivial? (Score:1)
I thought time evolution in quantum mechanics was given by unitary operators, which are always invertible. What's so interesting?
Phase conjugation and time reversal (Score:3)
I came here to say that phase conjugation is not time reversal but I thought about it some more and there are limited ways you might call it pseudo time reversal.
Phase conjugation of a light wave is old stuff. When you do it reverses the direction a shaped wavefront propagates. Since the argument of a wave function f(k*z-w*t) goes backwards when you change the sign on t it's mathematically the same as making time negative. So the wave goes back to where it came from. Notably if it went through phase dis
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I just modded you up as informative - but most of what you said was beyond my understanding. Too bad there isn't an "Informative - I think..." mod option. ;-)
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The dead giveaway that all this is fake news is that the quantum computer wasn't moving. Everyone knows that it has to be moving at precisely 88 miles per hour.
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The dead giveaway that all this is fake news is that the quantum computer wasn't moving. Everyone knows that it has to be moving at precisely 88 miles per hour.
or look like British Police box and be bigger on the inside...
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Boo that !!
Worst... Headline... EVAR! (Score:1)
The experiment was about reversing entropy, not actually reversing the flow of time.
That is interesting enough, why make up stupid headlines?
Same thing happened a ways back about some chemist unboiling an egg [livescience.com], which some copywriters (not linked article) tried to make it sound like time was being reversed.
Re:Worst... Headline... EVAR! (Score:5, Insightful)
I'm not sure they reversed entropy either. I thought that wasn't actually possible (much like time travel).
They took an electron and took it from state A to B and back to A. The energy required to go from B to A probably caused a net increase in entropy.
I concur though that it feels an ambitious headline. Does this mean I'm reversing time when I take a piss into the glass I drank out of?
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Everything in the universe is made up of stuff that is following the path of least resistance while hurling towards the future in a relentless, never-ending push to maximize the rate of entropy growth.
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Entropy is a rule based on probability.
So there is allways a miniscule chance that entropy spontanuously reverses.
And the smaller the system (for instance a couple of particles) the larger the chance of reversal.
Comment removed (Score:5, Funny)
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The universe will stop, and reverse time causing the everything to collapse into a singularity again. That means as the universe goes backwards, the dead will rise from the grave, humanity will eat excrement, un-chew food, and effectively vomit whole pieces of good. Oh, and you will reverse ageing until your a baby and get sucked up by a vagina.
Fun times.
This is the plot to "Yug Ylimaf" - the fourth episode of season 11 of Family Guy. This in turn may have been inspired by "Backwards' - the first episode of Red Dwarf.
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This in turn may have been inspired by "Backwards' - the first episode of Red Dwarf.
Well, the first episode of Red Dwarf’s third season, anyway...
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you will reverse ageing until your a baby and get sucked up by a vagina.
So as long as the average slashdotter can just find a way to live until nine months before the end of the universe, he won't die a virgin.
There's hope for everyone.
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I'm not sure they reversed entropy either. I thought that wasn't actually possible (much like time travel).
Everything in physics is reversible, though you have to reverse polarity and chirality when you reverse time.
Importantly, entropy works the same in both directions. A system in a state of low entropy will probably increase in entropy in both directions in time!
Here's an example. The classic example of entropy is that an egg breaking seems natural, but an broken egg re-assembling itself is so unlikely as to seem impossible. But the change in entropy in breaking an egg is tiny compared to the change in en
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I'm not sure they reversed entropy either. I thought that wasn't actually possible (much like time travel).
Everything in physics is reversible, though you have to reverse polarity and chirality when you reverse time.
Importantly, entropy works the same in both directions. A system in a state of low entropy will probably increase in entropy in both directions in time!
Here's an example. The classic example of entropy is that an egg breaking seems natural, but an broken egg re-assembling itself is so unlikely as to seem impossible. But the change in entropy in breaking an egg is tiny compared to the change in entropy in digesting an egg. So what are the odds of an egg re-assembling itself from CHON atoms? Well, it happens so often we have a name for the process: chicken.
When played "forward" in time, a chicken uses energy to reduce entropy to form an egg, and that energy is released when the egg is digested. Played "backwards" in time, once again energy is used to reduce entropy to form an egg, and that energy is released in the chicken.
tldr: like everything else in physics, entropy looks about the same "backwards".
Everything in Physics is reversible if you have an Eraser, too
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The direction of time is just, like, your opinion man.
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I concur though that it feels an ambitious headline. Does this mean I'm reversing time when I take a piss into the glass I drank out of?
Only if it was Budweiser. Otherwise it wouldn't taste the same as before...
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You're not reversing time, but you are reversing entropy. I mean, that's kind of what living things do. They use energy sources to lower their own entropy. You're doing it constantly. If you stopped doing it, your entropy would start increasing and you'd die. It's very easy to decrease the entropy of a system, as long as you balance it out by dumping that entropy (and a little bit more for good measure) somewhere else.
The energy required to go from B to A probably caused a net increase in entropy.
Not probably, definitely. Thermodynamics isn't just a good idea, it's the law!
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It is reversing time, like me restoring my PC from a backup and resetting the system clock to the time of the backup. For my PC being a closed system, it would be like it is back in time, but the passage of time hasn't changed.
The real exciting thing, is having a reset option on a quantum computer.
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More bullshit (Score:1)
They did not "send it back in time" anymore than the antimatter travels back in time.
If time was a thermodynamic phenomenon, why doesn't shit get younger when you put it in the fridge?
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Do you actually store shit in the fridge? If so, why? Does it reduce the smell or something?
Yes and yes. I guess you're no microbiologist.
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The ability to recall a previous state and return to it. I've got an idea, should we call this new invention something like "memory"?
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Calculation reversed, not time (Score:1)
They reversed a calculation on a quantum computer. Time was moving forward throughout the entire experiment.
Maybe some part of their algorithm might be useful somehow, but overall it seems like they were wasting time rather than reversing it.
Undo-Redo pattern (Score:5, Funny)
This doesn't prove time reversal, it show a quantum computer can unreliably implement the Undo-Redo pattern.
Re:Undo-Redo pattern (Score:5, Funny)
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Make Time Travel Great Again
Much better than the Democrat's desire for the 1850s.
How DARE you leave the thought plantation!
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Democrat's don't want to carry us back then. There were no social programs then (it's a wonder anybody survived).
No. They want to transport us physically....to Russia...so they can have their full-fledged socialism.
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It's a start.
So they can turn back time? (Score:5, Funny)
Somebody tell Cher!
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She can KEEP her 1/10th-nanosecond!
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Maybe she won’t marry Sonny this time. ... but then they’ll have to redo the sound track for Groundhog Day.
Errors Huh? (Score:2)
"in 85 percent of the cases, the two-qubit quantum computer returned back into the initial state," ... According to the authors, these errors are due to imperfections in the actual quantum computer.
Maybe the amazing headline result is due to one of these errors, rather than the null hypothesis being due to errors?
i call bullshit (Score:2)
Terrible Article (Score:1)
Article title misleading (Score:5, Insightful)
Fredkin gates? (Score:2)
Is this accomplishment an implementation of reversible computing? [wikipedia.org]
So now we know.... (Score:2)
... why Deja Vu happens...
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It's not really traveling to the past (Score:5, Insightful)
Time Travel Convention (Score:2)
These will have been my thoughts on the subject.
FTFY
The convention on Time Travel will be held last week. Tickets went on sale next month. Get yours yesterday before they run out!
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Was daylight savings time involved? (Score:5, Funny)
Why do I feel they forgot to carry the 2 ? (Score:2)
I can't wait to see if this was a IEEE floating point rounding problem.